Draft Regulator Specifications and 
Regulator Specification Test Code 
Sheets 
Date: December 2022 
 We are the Department for Environment, Food and Rural Affairs. We’re responsible for 
improving and protecting the environment, growing the green economy, sustaining thriving rural communities and supporting our world -class food, farming and fishing industr ies. 
 
We work closely with our 33 agencies and arm’s length bodies on our ambition to make our air purer, our water cleaner, our land greener and our food more sustainable. Our mission is to restore and enhance the environment for the next generation, and to leave the environment in a better state than we found it.  
 
 
© Crown copyright 202 2 
This information is licensed under the Open Government Licence v3.0. To view this 
licence, visit  www.nationalarchives.gov.uk/doc/open- government -licence/
  
This publication is available at www.gov.uk/government/publications    
Any enquiries regarding this publ ication should be sent to us at  
Department for Environment, Food and Rural Affairs,  
Water Services Team,  Ground Floor,  Seacole Building,  
2 Marsham Street,  
London,  
SW1P 4DF  
Or email at: drinkingwaterquality@defra.gov.uk
 
www.gov.uk/defra   
  page  
5 
19
 
42  
48 54 60 
69 
80 91 97 Contents 
Regulator S pecifications 
Specification for the prevention of B ackflow 
WC S uite Performance Specification 
Regulator S pecification Test C ode Sheets 
Test Code Sheet 15 11.2 Flush Rate 
Test Code Sheet 15 12.12 Wash of bow l 
Test Code Sheet 16 11.16 Liquid contaminant, dye  retention 
Test Code Sheet 22 12.3 Type AG – Vacuum / D imensional 
Test Code Sheet 22 13.15 Type AC – Dimensional 
Test Code Sheet 22 13.20 Type AUK4 
Test Code Sheet 22 13.21 Joints bel ow critical w ater l evel 
Test Code Sheet 5 011.7 Warning pipe and overflow provision 
To be withdrawn 
Test Code Sheet 50 11.5 Overflow – Measurement of di mension 104   
 
Regulator Specifications:  
    
 
Specification for the prevention of Backflow  
    
 
 
 
 
Draft Specification on the Prevention 
of Backflow 
Specification for backflow prevention devices and 
arrangements  
Date: December  2022 
 
  
We are the Department for Environment, Food and Rural Affairs. We’re responsible for 
improving and protecting the environment, growing the green economy, sustaining thriving rural communities and supporting our world -class food, farming and fishing industr ies. 
 
We work closely with our 33 agencies and arm’s length bodies on our ambition to make our air purer, our water cleaner, our land greener and our food more sustainable. Our mission is to restore and enhance the environment for the next generation, and to leave the environment in a better state than we found it.  
 
 
 
© Crown copyright 2021 
This information is licensed under the Open Government Licence v3.0. To view this 
licence, visit  www.nationalarchives.gov.uk/doc/open- government -licence/
  
This publication is available at www.gov.uk/government/publications    
Any enquiries regarding this publication should be sent to us at  
Department for Environment, Food and Rural Affairs,  
Water Services Team,  Ground Floor,  Seacole Building,  
2 Marsham Street,  
London,  
SW1P 4DF  
Or email at: drinkingwaterquality@defra.gov.uk
 
www.gov.uk/defra   
   
Contents  
Introduction  ..........................................................................................................................3  
Conformity testing  ................................................................................................................4  
Schedule 2: Paragraph 15 Backflow prevention ..................................................................4  
Backflow prevention arrangements and devices  ..................................................................5  
1. General interpretation of terms relating to backflow prevention  ....................................5  
2. Interpretations of backflow prevention arrangements as listed in Table 1  ....................6  
3. General interpretations of backflow prevention devices as listed in Table 2  .................8  
Fluid category backflow prevention suitability for arrangements and devices  ......................9  
Table 1: Schedule of non- mechanical backflow prevention arrangements and the 
maximum  permissible  fluid category  for which they  are acceptable  ..................................9  
Table 2: Schedule of mechanical backflow prevention arrangements and the maximum 
permissible fluid category for which they are acceptable  ................................................11  
Introduction  
The Water Supply (Water Fittings) Regulations 1999 1 (the ‘Regulations’) , have the 
specific purpose to prevent the waste, misuse, undue consumption, contamination or 
erroneous measurement of public water supplies , meaning those supplied by a water 
undertaker (an appointed water company) or a water supply licensee 2.  
The Regulations apply to any water fitting installed or used, or to be installed or used, in premises to which water is or is to be supplied by a water undertaker or water supply licensee. 
 
 
 
1 The Water Supply (Water Fittings) Regulations 1999 - 
https://www.legislation.gov.uk/uksi/1999/1148/contents  
2 Ofwat: Licence and licensee holders - www.ofwat.gov.uk/regulated-companies/ofwat -industry -
overview/licences/   The Regulations set out the legal requirements for plumbing systems and play an 
important role in protecting public health, safeguarding public water supplies and promoting the efficient use of water within premises. The Regulator, which is the Secret ary 
of State or  Welsh Ministers , can approve specifications to ensure fittings are of an 
appropriate quality and standard and suitable for the circumstances in which they are used. They can also approve specifications to ensure fittings are installed, connected, altered, repaired or disconnected in a workmanlike manner.  
This specification  sets out  the different types of arrangements and devices available for 
preventing backflow and back -siphonage (see sections 2 and 3) and, in tables  1 and 2,  
those fluid categories for which each arrangement and device is suitable. This specification is accompanied by a series of Test Code Sheets . 
Conformity testing  
When using a Regulator Specification or standard to demonstrate conformity  with 
Regulation 4(1)(a) , that manufacturers should, as good practice,  have in place a 
documented system of assessment of the performance of the backflow prevention 
arrangement or device. They should also have factory production controls to ensure 
consistency of manufacturing and product performance as described in the C onstruction 
Products Regulations 2011 as amended. 
Schedule 2: Paragraph 15 Backflow 
prevention  
15. 
(1) Subject to the following provisions of this paragraph, every water system shall 
contain an adequate device or devices for preventing backflow of fluid from any appliance, fitting or process from occurring.  
(2) Paragraph (1) does not apply to- 
(a) a water heater where the expanded water is permitted to flow back into a 
supply pipe, or  
(b) a vented water storage vessel supplied from a storage cistern,  
where the temperature of the water in the supply pipe or the cistern does not exceed 25°C.  
(3) The device used to prevent backflow shall be appropriate to the highest applicable fluid category to which the fitting is subject downstream before the next such device.  (4) Backflow prevention shall be provided on any supply pipe or distributing pipe-  
(a) where it is necessary to prevent backflow between separately occupied 
premises, or  
(b) where the water undertaker has given notice for the purposes of this Schedule that such prevention is needed for the whole or part of any premises . 
(5) A backflow prevention device is adequate for the purposes of paragraph (1) if it is in accordance with a specification approved by the regulator for the purposes of this Schedule.  
Backflow prevention arrangements and 
devices  
1. General interpretation of terms relating to 
backflow prevention  
“An air gap”  means a visible, unobstructed and complete physical air break between the 
lowest lev el of water discharge and the level of potentially contaminated fluid downstream 
(critical water level) within a cistern, vessel, fitting or appliance, hereinafter called a receptacle, that:  
(a) is not less than 20 mm or twice the internal diameter of the inlet pipe whichever is 
the greater; and  
(b) from which water discharges at not more than 15° from the vertical centreline of the 
water stream.  
“Critical level”  means the physical or piezometric level of the fluid in any part of the 
receptacle two seconds after cl osing the water inlet, starting from maximum water level.  
“Maximum level ” means the highest physical or piezometric level of the fluid reached in 
any part of the receptacle when operated continuously under fault conditions . 
“Spillover  level ” means the level at which the fluid in a receptacle will first spill over the 
top edge of a receptacle if the inflow of water exceeds the outflow through any outlet and 
any overflow pipe.  
“Tap gap”  means the vertical distance between the lowest part of a tap outlet and the 
spillover level of the appliance or receptacle over which the tap disc harges.  
An “upstand”  means either one of two alternative arrangements of water fittings to prevent 
backflow by back -siphonage:  Type  A upstand  An upward flowing supply or distributing pipe surmounted by 
an anti -vacuum valve (Type DA), or an anti -vacuum valve 
combined with a single check valve (Type DUK1), any part of 
the outlet of which is located not less than 300mm above the 
spillover level of an appliance  
Type B upstand  A branch pipe serving an appliance, where the height of any part of the branch connect ion to the vented distributing pipe is 
not less than 300 mm above:  
a. the spillover level of the appliance; or  
b. the highest possible discharge point served by the vented distributing pipe, whichever is the highest.  
“A verifiable backflow prevention device”  means a device, consisting of one or more 
backflow prevention elements, which can be tested in- situ; usually achieved by the 
provision of test ports immediately upstream, and between, the mechanical elements comprising the device.  
“flushing device ” means a device fitted to a flushing cistern to provide controlled 
measured volume(s) of water for flushing the receiving vessel (e.g. to a WC pan).  
NOTE : A flushing device can be a siphon, drop valve, flap valve or pressurised 
cistern etc. For the purposes of this specification, the flushing device includes the 
activator (i.e. handle, button, linkages, etc.) and all seals, pistons, or other integral 
components.  
2. Interpretations of backflow prevention 
arrangements as listed in Table 1 
“Type AA -  Air gap w ith unrestricted discharge ” means a non- mechanical backflow 
prevention arrangement of water fittings where water is discharged through an air gap into a receptacle which has at all times an unrestricted spillover to the atmosphere.  
“Type AB -  Air gap with weir overflow ” means a non -mechanical backflow prevention 
arrangement of water fittings complying with Type AA, except that the air gap is the 
vertical distance from the lowest point of the discharge orifice which discharges into the 
receptacle, to the cri tical level of the rectangular weir overflow.  
“Type AC -  Air gap with vented submerged inlet and circular overflow ” means a non-
mechanical backflow prevention arrangement of water fittings with a vented, but submerged, inlet; the air gap being measured ver tically downwards from the lowest point 
of the air inlet to the critical level.  “Type AD -  Air gap with injector ” means a non- mechanical backflow prevention 
arrangement of water fittings with a horizontal injector and a physical air gap of 20 
millimetres or twice the inlet diameter, whichever is the greater.  
“Type AF - Air gap with circular overflow ” means a non- mech anical backflow prevention 
arrangement of water fittings with an air gap measured downwards from the lowest point of the discharge orifice, which discharges into the receptacle, to the critical level.  
“Type AG -  Air gap arrangement with minimum size circul ar overflow ” means a non-
mechanical backflow prevention arrangement of water fittings with an air gap; together with an overflow, the size of which is determined by measure or a vacuum test.  
“Type AUK1 -  Air gap with interposed cistern”  means a non -mechani cal backflow 
prevention arrangement consisting of a cistern with a Type AG overflow and an air gap; 
the spillover  level of the receiving vessel (WC pan or other receptacle) being located not 
less than 300 millimetres below the overflow pipe and not less than 15 millimetres below 
the lowest level of the interposed cistern.  
Note in the case of WC suites within the Regulator’s Specification Test Code Sheet 2213.14 (Type AUK1 air gaps), reference to the distance from the spillover level of the receiving vessel and the invert of the “warning pipe” can be taken to be the 
dimension from the spillover level of the receiving vessel and invert of the overflow pipe.  
“Type AUK2 -  Domestic tap gap ” means the height of air gap between the lowest part of 
the outlet of a ta p, combination fitting, shower head or other fitting discharging over a 
domestic sanitary appliance or other receptacle, and the spillover level of that appliance, where a fluid category 2 or 3 risk is present downstream . 
“Type AUK3 -  Higher risk tap gap ” means the height of an air gap between the lowest 
part of the outlet of a tap, combination fitting, shower head or other fitting discharging over any appliance or other receptacle, and the spillover level of that appliance, where a fluid category 4 or 5 ri sk is present downstream . 
“Type AUK4  - Air gap with interposed flushing cistern ” means a non- mechanical 
backflow prevention arrangement consisting of a flushing cistern feeding by gravity a receiving vessel; the interposed flushing cistern incorporating a Type AG or Type AC air 
gap; an overflow; the spillover level of the receiving vessel (e.g. WC pan) being located not less than 150 millimetres below the overflow pipe (or combined warning/overflow pipe), and not less than 15 millimetres below the internal spillover level with all devices (e.g. 
flushing valve and associated attachments)  completely removed.  
“Type DC -  Pipe interrupter with permanent atmospheric vent ” means a non-
mechanical backflow prevention device with a permanent unrestricted air inlet, the device 
being installed so that the flow of water is in a vertical downward direction.  3. General interpretations of backflow prevention 
devices as listed in Table 2 
“Type BA -  Verifiable backflow preventer with reduced pressure zone”  means  a 
verifiable mechanical backflow prevention device consisting of an arrangement of water 
fittings with three pressure zones with differential obturators and that will operate when potential backflow conditions obtain or there is a malfunction of the valve.  
“Type CA -  Non-verifiable disconnector with different pressure zones”  means a non -
verifiable mechanical backflow prevention device which provides disconnection by venting the intermediate pressure zone of the device to the atmosphere when the difference of 
pressure between the intermediate zone and the upstream zone is not greater than 10% of 
the upstream pressure.  
“Type DA -  Anti-vacuum valve (or vacuum breaker) ” means a mechanical backflow 
prevention device with an air inlet which is closed when water w ithin the device is at or 
above atmospheric pressure but which opens to admit air if a vacuum occurs at the inlet to the device.  
“Type DB -  Pipe interrupter with atmospheric vent and moving element ” means a 
mechanical backflow prevention device with an air  inlet closed by a moving element when 
the device is in normal use but which opens and admits air if the water pressure upstream of the device falls to atmospheric pressure, the device being installed so that the flow of water is in a vertical, downward di rection.  
“Type DUK1 -  Anti-vacuum valve combined with a single check valve ” means a 
mechanical backflow prevention device comprising an anti -vacuum valve with a single 
check valve located upstream.  
“Type EA -  Verifiable single check valve”  means a verifiable mechanical backflow 
prevention device which will permit water to flow from upstream to downstream but not in the reverse direction.  
“Type EB -  Non-verifiable single check valve”  means a non- verifiable mechanical 
backflow prevention devi ce which will permit water to flow from upstream to downstream 
but not in the reverse direction.  
“Type EC -  Verifiable double check valve ” means a verifiable mechanical backflow 
prevention device consisting of two verifiable single check valves in series, which will permit water to flow from upstream to downstream but not in the reverse direction.  
“Type ED -  Non-verifiable double check valve”  means a non- verifiable mechanical 
backflow prevention device consisting of two single check valves in series, which will 
permit water to flow from upstream to downstream but not in the reverse direction.  “Type HA - Hose union backflow preventer ” means a mechanical prevention backflow 
device for fitting to the outlet of a hose union tap and consisting of a single check v alve 
with air inlets that open if the flow of water ceases.  
“Type HC - Diverter with automatic return ” means a mechanical backflow prevention 
device used in bath/shower combination tap assemblies which automatically returns the 
bath outlet open to atmosphere if a vacuum occurs at the inlet to the device.  
“Type HUK1 - Hose union tap incorporating a double check valve ” means a hose 
union tap in which a double check valve has been incorporated into either the inlet or outlet of the tap.  
“Type LA - Pressurised air inlet valve” means an anti -vacuum valve or vacuum breaker, 
similar to  Type DA but suitable for conditions where the water pressure at the outlet of the 
device under normal conditions of use is greater than atmospheric.  
“Type LB - Pressurised air inlet valve combined with a check valve downstream ” 
means a mechanical backflow  prevention device comprising a Type LA anti -vacuum valve 
and a single check valve located downstream.  
Fluid category backflow prevention s uitabi lity 
for arrangements and devices  
Table  1: Schedule of non-mechanical backflow 
prevention arrangements and the maximum  
permissible  fluid category  for which they  are 
acceptable  
Type  
 Description of backflow prevention 
arrangements and devices  Suitable for 
protection against 
fluid category  
Back-
pressure  Back-
siphonage  
AA Air gap with unrestricted discharge above spillover 
level 5 5 
AB Air gap with weir overflow  5 5 
AC Air gap with vented submerged inlet  3 3 
AD Air gap with injector  5 5 Type  
 Description of backflow prevention 
arrangements and devices  Suitable for 
protection against 
fluid category  
Back-
pressure  Back-
siphonage  
AF Air gap with circular overflow  4 4 
AG Air gap with minimum size circular overflow 
determined by measure or vacuum test  3 3 
AUK1  Air gap with interposed cistern (For example, a WC 
suite)  3 5 
AUK2  Air gaps for taps and combination fittings (tap gaps) 
discharging over domestic sanitary appliances, such as a washbasin, bidet, bath or shower tray shall not be less than the following:  
Size of tap or  Vertical distance of bottom of tap 
combination fitting outlet  above spillover level of  
 receiving appliance  
Not exceeding G ½  20 mm  
Exceeding G ½ but not  
exceeding G ¾  25 mm  
Exceeding G ¾  70 mm  X 3 
AUK3  Air gaps for taps or combination fittings (tap gaps) 
discharging over any higher risk domestic sanitary 
appliances where a fluid category 4 or 5 is present, 
such as:  
a any domestic or non- domestic sink or other 
appliance; or  
b any appliances in premises where a higher level 
of protection is required, such as some 
appliances in hospitals or other health care 
premises,  
shall be not less than 20 mm or twice the diameter of 
the inlet pipe to the fitting, whichever is the greater.  X 5 
AUK4 Air gap with interposed flushing cistern (for example in a WC suite)  3 5 Type  
 Description of backflow prevention 
arrangements and devices  Suitable for 
protection against 
fluid category  
Back-
pressure  Back-
siphonage  
DC Pipe interrupter  with permanent  atmospheric  vent X 5 
Notes:  
1 X Indicates that the backflow prevention arrangement or device is not applicable or 
not acceptable for protection against backpressure for any fluid category within 
water installations in the UK.  
2 Arrangements incorporating Type DC devices shall have no control valves on the outlet of the device; they shall be fitted not less than 300 mm above the spillover level of a WC pan, or 150 mm above the sparge pipe outlet of a urinal, and discharge vertically downwards .  
3 Overflows and warning pipes shall discharge through, or terminate with, an air gap, the dimension of which should satisfy a Type AA air gap.  
Table  2: Schedule of mech anical backflow 
prevention arrangements and the maximum 
permissible fluid category for which they are 
acceptable  
Type  
 Description of backflow prevention 
arrangements and devices  Suitable for 
protection against 
fluid category  
Back-
pressure  Back-
siphonage  
BA Verifiable backflow preventer with reduced pressure 
zone  4 4 
CA Non-verifiable disconnector with difference between 
pressure zones not greater than 10%  3 3 
DA Anti-vacuum valve (or vacuum breaker)  X 3 Type  
 Description of backflow prevention 
arrangements and devices  Suitable for 
protection against 
fluid category  
Back-
pressure  Back-
siphonage  
DB Pipe interrupter with atmospheric vent and moving 
element  X 4 
DUK1  Anti-vacuum valve combined with a single check 
valve 2 3 
EA Verifiable single check valve  2 2 
EB Non-verifiable single check valve.  2 2 
EC Verifiable double check valve  3 3 
ED Non-verifiable double check valve  3 3 
HA Hose union backflow preventer. Only permitted for use on existing hose union taps in house installations  2 3 
HC Diverter with automatic return (Normally integral with 
some domestic appliance applications only)  X 3 
HUK1  Hose union tap which incorporates a double check valve. Only permitted for replacement of existing 
hose union taps in house installations  3 3 
LA Pressurised air inlet valve  X 2 
LB Pressurised air inlet valve combined with a check 
valve downstream  2 3 Type  
 Description of backflow prevention 
arrangements and devices  Suitable for 
protection against 
fluid category  
Back-
pressure  Back-
siphonage  
Notes:  
1 X Indicates that the backflow prevention device is not acceptable for protection 
against backpressure for any fluid category within water installations in the UK.  
2 Arrangements incorporating a Type DB device shall have no control valves on the 
outlet of the device. The device shall be fitted not less than 300mm above the 
spillover level  of an appliance and discharge vertically downwards .  
3 Types DA and DUK1 shall have no control valves on the outlet of the device and 
be fitted on a 300 mm minimum Type A upstand.  
4 Relief outlet ports from Types BA and CA backflow prevention devices shall 
terminate with an air gap, the dimension of which should satisfy a Type AA air gap.  
   
 
WC Suite Per formance Specification  
    
 
 
 
 
Draft WC Suite Performance 
Specifications  
Specification for WC Suites delivering a single flush of 
6 litres maximum or a dual -flush of 6 litres maximum 
and reduced flush of no greater than 2/3 of the maximum flush  
Date: December 2022 
 
  
We are the Department for Environment, Food and Rural Affairs. We’re responsible for 
improving and protecting the environment, growing the green economy, sustaining thriving rural communities and supporting our world -class food, farming and fishing industries. 
 
We work closely with our 33 agencies and arm’s length bodies on our ambition to make our air purer, our water cleaner, our land greener and our food more sustainable. Our mission is to restore and enhance the environment for the next generation, and to leave the environment in a better state than we found it.  
 
 
 
© Crown copyright 2021 
This information is licensed under the Open Government Licence v3.0. To view this 
licence, visit  www.nationalarchives.gov.uk/doc/open- government -licence/
  
This publication is available at www.gov.uk/government/publications    
Any enquiries regarding this publication should be sent to us at  
Department for Environment, Food and Rural Affairs,  
Water Services Team,  Ground Floor,  Seacole Building,  
2 Marsham Street,  
London,  
SW1P 4DF  
Or email at: drinkingwaterquality@defra.gov.uk
 
www.gov.uk/defra   
 
  Contents  
Introduction  ..........................................................................................................................5  
Conformity testing  .............................................................................................................5  
Scope...................................................................................................................................6  
Normative references ...........................................................................................................6  
Definitions  ............................................................................................................................7  
Performance Requirements  ................................................................................................. 9 
General tolerances and measurements  ............................................................................9  
1 Inlet valve  ........................................................................................................................10  
1.1 Performance  .............................................................................................................10  
1.2 Anti -siphonage capability  ..........................................................................................11  
1.3 Joints below the water line ........................................................................................11  
2 Flushing devices  .............................................................................................................12  
2.1 Physical endurance and leakage  ..............................................................................12  
2.2 Chemical endurance  ................................................................................................. 13 
3 Flushi ng cisterns  .............................................................................................................14  
3.1 Marking  .....................................................................................................................14  
3.2 Warning  and Overflow  Pipe Provision  .......................................................................14  
3.3 Flush Volume  ............................................................................................................15  
3.4 Flush rate ..................................................................................................................16  
4 Water Closet Suite  ..........................................................................................................17  
4.1 Solids discharge and after -flush volume for maximum flush  .....................................17  
4.2 Paper discharge for reduced flush volume  ...............................................................18  
4.3 Liquid contaminant dye retention  ..............................................................................19  
4.4 Wash of Bowl  ............................................................................................................19  
4.5 Water seal depth  ......................................................................................................20  Informative Annex - Summary Requirements for Compatibility Testing  .............................21  
  Introduction  
The Water Supply (Water Fittings) Regulations 19991 (the ‘Regulations’) , have the specific 
purpose to prevent the waste, misuse, undue consumption, contamination or erroneous 
measurement of public water supplies, meaning those supplied by a water undertaker (an 
appointed water company) or a water supply licensee 2. 
The Regulations  apply to any water fitting installed or used, or to be installed or used, in 
premis es to which water is or is to be supplied by a water undertaker or water supply 
licensee.  
The Regulations set out the legal requirements for plumbing systems and play an 
important role in protecting public health, safeguarding public water supplies and 
promoting the efficient use of water within premises.  The Regulator,  which is the Secretary 
of State or Welsh Ministers , can approve specifications to ensure fittings are of an 
appropriate quality and standard and suitable for the circumstances in which they are used.  They can also approve specifications to ensure fittings are installed, connected, 
altered, repaired or disconnected in a workmanlike m anner.  
This specification sets out the performance and where necessary dimensional requirements expected from Water Closet (WC) suites and key components  within them . 
These include inlet valves, flushing devices  and flushing cisterns.  This specification is  
accompanied by a series of Test Code Sheets.  
Conformity testing  
Manufacturers of WC suites or an independent component of a suite shall demonstrate they are of a suitable quality and standard through conformity with this specification.  
In addition manufac turers should, as good practice,  have in place a documented system of 
assessment of the performance of the product and factory production controls to ensure consistency of manufacturing and product performance as described in the Construction Products Regulations 2011 as amended. 
 
 
 
1 The Water Supply (Water Fittings) Regulations 1999 - 
https://www.legislation.gov.uk/uksi/1999/1148/contents  
2 Ofwat: Licence and licensee holders - www.ofwat.gov.uk/regulated-companies/ofwat -industry -
overview/licences/   The expectation of this specification is that any element of a WC Suite offered for sale 
independently should enable other associated elements to meet the essential performance 
characteristics (parts 1 to 4)  of this specification w hen combined to form a WC Suite.  
Nonetheless, it is clearly unreasonable for the manufacturer of an independent component that may be used in a suite to ensure that the product would satisfy the requirements if installed with every other available other part that could make up a WC suite. Therefore, component manufacturers need to complete those tests relevant to their product and 
ensure that when installed as part of a whole WC suite their product would be capable of fulfilling the complete set of tests. W hosoever selects the components to form a WC suite 
should ensure that they form a compliant suite which satisfies all the tests in this specification (see Informative Annex).  
Scope 
This specification sets performance requirements and methods of test for W C suites 
designed to operate with either a pressure flushing valve or a flushing cistern incorporating some other flushing device. The WC Suite shall be capable of delivering a maximum flush volume of 6 litres or a dual -flush combining a maximum flush volu me of 6 litres and a 
reduced flush volume no greater than two thirds of the maximum flush volume.  
NOTE: This specification does not  cover  backflow prevention requirements (see 
Informative Annex) , which need to be considered separately . 
Normative references  
This specification incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subse quent amendments 
to or revisions of any of these standards apply to this specification only when incorporated 
in it by amendment or revision. For undated references the latest edition of the standard referred to applies.  
• BS 1212- 2 Float operated valves -  Specification for diaphragm type float operated 
valves (copper alloy body) (excluding floats).  
• BS 1212- 3 Float operated valves -  Specification for diaphragm type float operated 
valves (plastics bodied) for cold water.  
• BS 1212- 4 Float operated valves -  Speci fication for compact type float operated 
valves for WC flushing systems (including floats).  
• TCS 1211.15 Flushing device physical endurance and leakage  
• TCS 1411.3 Flushing device chemical endurance 
• TCS 1511.2 Flush rate  • TCS 1512.10 Paper discharge for reduced flush volume  
• TCS 1512.11 Solids discharge and after flush volume for maximum flush  
• TCS 1512.12 Wash of Bowl  
• TCS 1611.16 Liquid contaminant dye retention 
• TCS 2212.20 Backflow prevention Regulator ’s specification for WC suites (anti -
siphonage capabil ity) 
• TCS 2213.21 Joints below critical water level  
• TCS 3212.1 WC flush volume and water seal depth  
• TCS 5011.6 Water seal depth  
• TCS 5011.7 Warning pipe and overflow provision 
• TCS 6001.1 Marking for identification  
Definitions  
For the purposes  of this specifi cation the following  definitions  apply:  
After -flush volume  
Remaining flush water volume after the last of four specimens have left the outlet of the 
bowl. 
Critical level  
The physical or piezometric level of the fluid in any part of the receptacle two seconds after closing the water inlet, starting from maximum water level. [source the Regulations, 
Regulator’s Specification on the Prevention of Backflow : 1 General interpretation of terms 
relating to backflow prevention]  
Dual flush  
Flushing cisterns with two modes of operation, one delivering a larger volume than the other, in which:  
• the larger (full) flush option is not greater than 6 litres; and  
• the reduced smaller flush option is not greater than two- thirds the volume of the 
larger flush.  
Fluid contaminant  
Liquid to be removed from WC pan by flushing action.  Flush volume  
Volume of water discharged from the flushing device during a flush cycle.  
NOTE: In the case of devices that require a continuous water supply during flushing 
(e.g. for outlet seal and/or trap refill) the inflow during flushing forms part of the flush 
volume.  
Flushing Device  
Device fitted to a flushing cistern to provide controlled measured volume(s) of water to a 
WC for flushing.  
NOTE A flushing device can be a siphon, drop valve, flap valve or pressurised 
cistern etc. For the purposes of this specification, the flushing device includes the activator (i.e. handle, button, linkages, etc.) and all seals, pistons, or other integral components.  
Inlet valve  
Valve that controls and shuts off the flow of water into a flushing cistern, usually by an arm 
connected to a float . 
Residual fluid contaminant  
Liquid waste left behind in the WC bowl after completion of the flush.  
Regulations  
In this specification  means the Water Suppl y (Water Fittings) Regulations 1999.  
Regulator’s Specification Test Code Sheet (TCS)  
A technical specification which detail specific testing procedures which, either on their own or in combination with other TCSs, verify a water fitting (s) is of a suitable quality and 
standard and or in compliance with the requirements of the Regulations  or accompanying 
Regulator’s Specifications . 
Solid test media  
Media used to represent faecal matter . 
Warning level  
Level of spillover of a vertically mounted warning pipe connection or the invert of a horizontally mounted warning pipe connection, or the level at which an equally effective (warning) device would operate.  Warning pipe  
Means an overflow pipe whose outlet is located in a position where the discharge of water 
can be readily seen. [source the Regulations , Schedule 2: Paragraph 25 (7): WC's, 
flushing devices and urinals] . 
Water trap  
Water seal that prevents backflow of odour from a drain.  
WC suite  
WC Pan combined with either a flushing cistern with integral warning pipe connection -  or a 
device deemed to be no less effective -  and inlet/outlet devices, or a pressure flush  valve,  
with WC and flushing device installed  as a functioning unit. 
Performance Requirements  
General t olerance s and measurements  
In the absence of specific tolerances or accuracies for  measuring instruments the following 
shall apply.  
Tolerances and measurements  
1. Dimension : up to and including 75 mm ±5% ; over 75 mm ±2%. 
2. Flow rate and pressure: ± 5 % of the value specified.  
3. Temperature:  cold water ± 10 °C of the value specified.  
Accuracy of measuring instruments  
All the measuring instruments shall have an error limit of ±2 % of the measured value.  
Linear measuring instruments shall have a minimum res olution of 0. 5 mm 
Timing instruments shall have a minimum resolution of 0. 1 seconds  
Uncertainty of Measurement. When testing there should be in place a scheme of 
Uncertainty of Measurement to determine the budget range. The budget (See Figure 1) 
should acc ount for the variations (instrumentation, equipment etc.) that might occur 
throughout all stages of the testing process. Where Uncertainty of Measurement budget is likely to cross over the acceptance limit given by the requirement, it should be reported with the test result . Figure 1: Reporting uncertainty of measurement budgets  
 
1 Inlet valve  
An inlet valve for use within a WC suite, and satisfy this Specification,  shall be of an 
appropriate quality and standard (see Regulation 4) complying with BS  1212 Parts 2, 3, or 
4, subject to t he following essential characteristics  of: performance (1.1), anti-siphonage 
capability (1.2) and have no joints below the critical water  level (1.3) . 
1.1 Performance  
1.1.1 Requirement  
Inlet valves shall comply with  BS 1212 Parts 2, 3, or 4 , subject to the amendments  
specified below:  
Water quality  
• The water hardness during tests shall not exceed the range of 230 ±20 ppm of 
calcium carbonate during the course of the test . 
Endurance  
• The endurance test shall be undertaken for 200,000 cycles; and if the first inlet 
valve fails the test, the four valves subsequently tested must all satisfy the requirements.  
• The supply pressure for the endurance test shall be 1.5 ± 0.1 bar. 
• Inlet valves to BS 1212-2 :1990 shall be subject to an endurance test as described 
in BS 1212-3 :1991 using a supply pressure of 1.5 ±0.1 bar . Pa ss
(Pa sse s , within limits )Conditional Pas s
(Pa sse s , but overlaps  limits )Conditional Fail
(Fails , but overlaps  limit )Fail
(Fails , exceeds  limits )
Boundary of upper uncertainty
Boundary of lower uncertaintyReading tak enUpper limit
{Uncertainty of Meas urement budget1.1.2 Test method  
i Apparatus  
Apparatus as specified in BS  1212 subject to the additional requirements specified in 
Clause 1.1.1. Supply pressure requirements for pressurised cisterns shall conform with the 
manufacturer's recommendations.  
ii Procedure  
Subject the inlet valve to the tests as specified in BS  1212 Parts 2, 3, or 4 as appropriate. 
In testing against the endurance clause of BS  1212 (modified in  Clause  1.1.1) if the first 
inlet valve fails, four further valves shall be tested.  
iii Expression of results  
Record compliance, or failure to comply with the requirements of the appropriate part of 
BS 1212 and Clause 1.1.1.  
1.2 Anti -siphonage  capability  
1.2.1 Requirement  
When tested in accordance with the requirements of Clause 1.2.2 there shall be no 
evidence of  back -siphonage . 
1.2.2  Test method  
i. Apparatus and procedure  
Inlet valves to BS 1212 part 2 or 3 shall be tested in accordance with Test Procedure 4 (A) 
of the Regulator’s Specification Test Code Sheet 2212.20.  
Inlet valves to BS 1212 part 4 shall be tested in accordance with Test Procedure 4 (B) of 
the Regulator’s Specification Test Code Sheet 2212.20.  
ii Expression of results  
Record compliance, or failure to comply with the requirements of Clause 1.2. 1. 
1.3 Joints below the water line 
1.3.1 Requirement  
When tested as described in Clause 1.3.2 no mechanical joint  within a flushing cistern on 
submerged supply pipes or inlet devices shall be at or below the critical water level.  Mechanical joints  are joints which when undone open a direct pathway between the 
wholesome water (incoming supply) and the fluids stored within the f lushing cistern. These 
include joints  that: 
a. are ‘adjustable’ or can be ‘dismantled’;  or 
b. rely on elastomeric, or other  material , to provide a water -tight seal; or  
c. where the coupling of two components being dependent upon mechanically 
applied forces, with or  without the use of secondary  seal.  
Joints not considered mechanical joints  include:  
a. Nuts or jointing mechanism on the diaphragm housing assembly.  
b. Joints where the joining surface are permanently fused together , for example 
by a chemical process or the application of heat.  
1.3.2 Test method  
i. Apparatus  and procedure  
The flushing cistern, complete with all fitments (e.g. inlet valve, flushing device, overflow 
etc.) installed in accordance with the manufacturer's instructions , shall be tested in 
accordance with Test Procedure 4 (A) of the Regulator’s Specification Test Code Sheet 2213.21.  
ii. Expression of results  
Record compliance, or failure to comply with the requirement s of 1.3.1 . 
2 Flushing devices  
2.1 P hysical endurance and leakage  
2.1.1 Req uirement  
When tested as described in Clause 2.2.1, the flushing device shall not undergo any 
failure or permanent distortion of any components including linkages that prevents normal operation of the mechanism.  
No more than 2 instances of leakage are permi tted. A leak is defined as being visible 
discharge of water amounting to more than 3 separate drops. If the first flushing device fails the test, the four devices  subsequently  tested  must  all satisfy the requirements.  2.1.2 Test method 
i Apparatus  and procedure  
The flushing cistern, complete with fitments including flushing device, flushpipe (where 
appropriate) and cover, installed in accordance with the manufacturer's instructions shall be tested in accordance with Test Procedure 4.1 of the Regulator’s Specification Test 
Code Sheet 1211.15.    
In Test Code Sheet 1211.15 the following definitions shall apply:  
Short term leak test  means a leak test consisting of a 15 minute wait after flushing 
then positioning paper designed to change colour when wet,  under the flushing device 
for 10 minutes. A leak is defined as being visible discharge of water amounting to more 
than 3 separate drops.  
Long term leak test  means a leak test consisting of a 2 hour wait after flushing then 
position paper, designed to chan ge colour when wet, under the outlet for 15 minutes. A 
leak is defined as being visible discharge of water amounting to more than 3 separate 
drops.  
ii Expression of results  
Record compliance, or any failure to comply, with the requirements of  Clause 2.1.1.  
2.2 C hemical endurance  
2.2.1 Requirement  
When tested as described in Clause 2.2.2, there shall be:  
• no dimensional alteration of any component greater than 1 mm or 5% whichever is 
the lesser;  
• no weight loss of any component greater than 1 g or 5% whichever is the lesser;  
• no visible sign of physical change such that performance is impaired;  
• no deterioration in performance.  
The flushing device shall not leak after undergoing a 3000 cycle physical endurance test 
and the long term leakage test  (see 2.1.2 i) . 
2.2.2 Test method  
i Apparatus  and procedure  
The flushing device shall be tested in accordance with Test Procedure 4 of the Regulator’s Specification Test Code Sheet 1411.3.  In TCS 1411.3 the definition of long term leak test  shall be taken as that given in 2.1.2 i 
above.  
ii Expression of results  
Record compliance, or any failure to comply with the requirements of  Clause 2.2.1 . 
3 Flushing cisterns 
3.1 Marking  
3.1.1 Requirement  
Every flushing cistern, other than a pressure flushing cistern, shall be clearly marked 
internally with an indelible line to show the intended volume of flush, together with an 
indication of that volume. Discharge volume(s) shall be based on measurement from the 
water level in the cistern using the manufacturer's original equipment to the residual water level in the cistern on completion of a flush.  
3.1.2 Test method  
i Apparatus and procedure  
The flushing cistern shall be tested in accordance with the appropriate Test Procedure 4.1 (C) of the Regulator’s Specif ication Test Code Sheet 6001.1.  
ii Expression of results  
Record compliance, or any failure to comply with the requirements of Clause 3.1.1.  
3.2 Warning  and Overflow  Pipe Provision  
3.2.1 Requirement  
i Point of discharge  
When tested as described in Clause  3.2.2, every flushing cistern, not being a pressure 
flushing cistern, shall be  arranged - 
a) in the case of a combined warning and overflow pipe-   
i. with the discharge level between 20 mm and 51 mm inclusive, above the marked water level.  
or b) in the case of separate warning and overflow pipes - 
i. fitted with a warning pipe connection arranged with the discharge level 
between 20 mm and 41 mm inclusive, above the marked water level ; and 
ii. the top edge of any internal overflow between 30 mm and 51 mm  inclusive 
and not less than 10 mm above the warning level.  
An alternative, no less effective device, may be used in place of a warning pipe.  
ii Size of overflow  and air gap to drain  
In the case of an internal overflow  within a WC suite , i.e. one that disc harges into the flush 
pipe or bowl , requirements relating to the overflow size and the provision of air gaps to 
drain,  need not apply provided : 
a) the overflow is not less than 19 mm internal diameter at the point water enters the overflow to be discharged; and  
b) the critical water level (h) has been verified by test.  
3.2.2 Test method  
i Apparatus  and procedure  
The flushing cistern with warning pipe connection or a device deemed to be no less 
effective and internal overflow, if provided, installed in accordance with the manufacturer's 
instructions, shall be tested in accordance with Test Procedure 4 ( A) of the Regulator’s 
Specification Test Code Sheet 5011.7.  
ii Expression of results  
Record compliance or any failure to comply with the requirements of  Clause 3.2.1.  
3.3 Flush Volume  
3.3.1 Requirement  
i Full Flush  
When tested as described in Clause 3.3.2 with any adjustable flushing device set to 
deliver the maximum flush volume, the measured discharge shall on no occasion exceed 6 litres.  ii Reduced flu sh 
When tested as described in Clause 3.3.2 with any adjustable flushing device set to 
deliver a reduced flush volume, the measured discharge shall on no occasion exceed two 
thirds of the full flush volume.  
3.3.2 Test method  
i Apparatus  and procedure  
The f lushing cistern, complete with fitments including flushpipe and cover, installed in 
accordance with the manufacturer's instructions, on a firm, flat, vertical surface shall be 
tested in accordance with Test Procedure 4 (A) of the Regulator’s Specification Test Code 
Sheet 3212.1.  
ii Expression of results  
Record compliance or any failure to comply with the requirements of Clause 3.3.1.  
Note it is also possible to record any failure of the trap seal depth to conform with the requirements of Clause 4.5.1 4.13.  
3.4 Flush rate  
3.4.1 Requirement  
When tested as described in Clause 3.4.2, the mean flush rate of discharge per flush shall be ≥1.85 L/s for the full -flush and ≥ 1.6 L/s for the reduced- flush - if provided.  
3.4.2 Test method  
i Apparatus  and procedure  
A flushing cistern, complete with fitments including flushpipe  (where appropriate)  and 
cover, installed in accordance with the manufacturer's instructions on a firm, flat, vertical surface, shall be tested in accordance with Test Procedure 4 (A) of the Regulato r’s 
Specification Test Code Sheet 1511.2.  
ii Expression of results  
Record compliance or any failure to comply with the requirements of Clause 3.4.1.  4 Water Closet Suite  
4.1 Solids discharge and after -flush volume for 
maximum flush  
4.1.1 Requirement  
When tested as described in Clause 4.1.2, for the first six flush cycles, or for a minimum of 
eight out of ten flush cycles, each of the four test specimens shall be completely 
evacuated from the WC bowl and pan's outlet. The recorded after -flush volume in each 
flush cycle shall be no less than 40% of the full flush volume.  
4.1.2 Test method  
i Apparatus  and procedure  
The WC pan with associated flushing cistern and/or flushing device, or a close-
coupled/one- piece suite, satisfying the requirements of this specification, installed in 
accordance with the manufacturer’s instructions on a firm, flat horizontal/vertical surface as appropriate, shall be tested in accordance with Test Procedure 4 (A) of the Regulator’s Specification Test Code Sheet 1512.11.  
In Test Code Sheet 1512.11 the following shall apply:  
(a) in 4.2 b) t he undated reference to “Annex F of BS EN 997”  shall be taken as the 
“‘Preparation of test specimens ’ of BS EN 997  WC pans and WC suites with integral 
trap”; and  
(b) in 4.2 f) the timing device is to have an accuracy of 0.05 seconds; and  
(c) in 4.2 g) reference to “ Figure 1” , and in 4.3 reference “Figure 1 of AS 1172.1:1993 ” 
can be taken as the directing device in Figure 2 below , with all dimensions given in 
millimetres . Figure 2: Directing device  
 
ii Expression of results  
Record compliance, or any failure to comply with the requirements of  Clause 4.1.1.  
4.2 Paper discharge for reduced flush volume  
4.2.1 Requirement  
When tested as described in Clause 4.2.2, for the first six flush cycles, or for a minimum of 
eight out of ten flush cycles, all six sheets of toilet paper shall be flushed out of the WC 
pan and outlet.  
4.2.2 Test method 
i Apparatus  and procedure  
The WC pan with associated flushing cistern and/or flushing device (satisfying the 
requirements of this specification), or a close- coupled/one- piece suite, installed in 
accordance with the manufacturer’s instructions on a firm, flat horizontal/vertical surfac e as 
appropriate, shall be tested in accordance with Test Procedure 4 (A) of the Regulator’s 
Specification Test Code Sheet 1512.10 . 
In Test Code Sheet 1512.10 clause 4.2 b) the undated reference to “Annex E of BS EN 
997” shall be taken as  the “‘Basket method’  of BS EN 997  WC pans and WC suites with 
integral trap” . 
ii Expression of results  
Record compliance or failure to comply with the requirements of  Clause 4.2.1 . 
4.3 Liquid contaminant dye retention  
4.3.1 Requirement  
When tested as described in Clause  4.3.2, for the first five flush cycles, or for a minimum 
of nine out of ten flush cycles at full -flush volume, the contaminate level shall be ≤ 1%. For 
the first five flush cycles, or for a minimum of nine out of ten flush cycles at reduced- flush 
volume, when pr ovided, the contaminate level shall be ≤ 6%. 
4.3.2 Test method 
i Apparatus  and procedure  
The WC pan with associated flushing cistern and/or flushing device (satisfying the 
requirements of this specification), or a close- coupled/one- piece suite, installed in 
accordance with the manufacturer’s instructions on a firm, flat horizontal/vertical surface as appropriate, shall be tested in accordance with Test Procedure 4 (A) of the Regulator’s Specification Test Code Sheet 1611.16.  
ii Expression of results  
Record c ompliance, or failure to comply with the requirements of  Clause 4. 3.1. 
4.4 Wash of Bowl  
4.4.1 Requirement  
When tested as described in Clause 4.4.2 the arithmetic average of any unflushed area 
below the rim and above the surface of the trap shall be no greater than 50 cm2 after 5 
flushing operations . For rimless WC pans the surface to be tested is the area between the 
water surface of the trap and a horizontal line 85 mm below the top edge of the bowl . 
4.4.2 Test method  
i Apparatus  and procedure  
The WC pan w ith associated flushing cistern and/or flushing device (satisfying the 
requirements of this specification), or a close- coupled/one- piece suite, installed in accordance with the manufacturer’s instructions on a firm, flat horizontal/vertical surface as 
appropriate, shall be tested in accordance with Test Procedure 4 (A) of the Regulator’s 
Specification Test Code Sheet 1512.12.  
ii Expression of results  
Record compliance, or any failure to comply with the requirements of  Clause 4.4.1.  
4.5 Water seal depth  
4.5.1 Requirement  
When tested twice as described in Clause 4.5.2 , the water seal depth shall be no less than 
50 mm on either occasion. If any alternative trap seal device is utilised, a no less effective comparable seal shall be in operation.  
4.5.2 Test method 
i Apparatus and procedure  
The WC pan with associated flushing cistern and/or flushing device, or a close-
coupled/one- piece suite, all meeting the appropriate requirements of this standard, 
installed in accordance with the manufacturer’s instructions on a firm, flat 
horizontal/vertical  surface as appropriate shall be tested in accordance with either:  
(a) Test Procedure 4 (A) of the Regulator’s Specification Test Code Sheet 3212.1, if 
combined with the flush volume test (see 3.3.2); or  
(b) Test Procedure 4 (A) of the Regulator’s Specification Test Code Sheet 5011.6.  
ii Expression of results  
Record compliance, or failure to comply with the requirements of Clause 4.5.1.  
  Informative Annex -  Summary Requirements 
for Compatibility Testing 
This annex provides further background notes on the testing and compatibility of elements 
of the WC suite for the purposes of this specification.  
Users should note WC suites will require appropriate backflow protection in addition to conformance with this specification. This can be incorporated within the design of the WC suite. Backflow prevention requirements are set out in p aragraph 15 of Schedule 2 of the 
Regulations. The Specification on the Prevention of Backflow  details appropriate 
arrangements within Table 1 which includes Type AUKWC arrangement s specifically  for 
use with flushing cisterns  and subject to certain characteristics  compatibility testing.  Where 
backflow prevention is not incorporated within the design, separate backflow prevention arrangement will be required on the upstream supply  
Inlet valves mus t satisfy BS 1212 as modified in section 1 and have no joints below the 
critical water level . 
Flushing devices must satisfy the requirements with regard to physical and chemical endurance. They must also be capable of satisfying the flush volume test at full and, if appropriate, reduced flush volumes. They should also be capable of contributing towards the other requirements when tested in combination.  
Cisterns must consist of compliant components and so satisfy warning pipe and overflow provisions and the flush volume test. They should be suitably marked for the intended full 
and, if appropriate, reduced flush volume of the WC pan. They should also be capable of 
contributing towards the other requirements when tested in combination.  
WC pans must, for their intended flush volume, satisfy the requirements regarding solid and paper discharge; after -flush volume; liquid dye contaminant retention; wash of bowl 
and trap seal depth.  
The whole WC suite must comprise of fully compliant components which, when installed 
together, satisfy all the tests.  
It should be noted that when undertaking tests involving more than one component of a 
WC suite, components which could adversely affect the results of the whole test should not be changed without re- starting that test.    
 
Regulator Specification Test Code 
Sheets:  
    
 
Test Code Sheet 1511.2 Flush Rate  
    
Test Code Sheet  1 5 1 1 ● 2  Draft Issue  No. 7 
        Date of Issue: December  2022  
Sheet  1 of 5 
 
1. PURPOSE 
Flushing Cisterns: Flush Rate verification as described in WC Suite Performance 
Specifications.  
2. TYPE OF TEST (S) 
Flush Rate.  
3. WATER REGULATIONS REQUIREMENTS FOR FITTINGS  
Schedule 2 
25. (1) Subject to the following provisions of this paragraph-  
a. every water closet pan shall be supplied with water from a flushing 
cistern, pressure flushing cistern or pressure flushing valve, and shall be so made and installed that after normal use its contents can be cleared effectivel y by a single flush of water, or, where the installation is designed 
to receive flushes of different volumes, by the largest of those flushes;  
b. no pressure flushing valve shall be installed-  
i. in a house, or  
ii. in any building not being a house where a minimum f low rate of 1.2 
litres per second cannot be achieved at the appliance;  
c. where a pressure flushing valve is connected to a supply pipe or distributing pipe, the flushing arrangement shall incorporate a backflow prevention device consisting of a permanently v ented pipe interrupter 
located not less than 300mm above the spillover level of the WC pan or  
urinal:  
d. no flushing device installed for use with a WC pan shall give a single 
flush exceeding 6 litres;  
e. no flushing device designed to give flushes of different volumes shall have a lesser flush exceeding two- thirds of the largest flush volume;  
f. every flushing cis tern, other than a pressure flushing cistern, shall be 
clearly marked internally with an indelible line to show the intended volume of flush, together with an indication of that volume;  Test Code Sheet  1 5 1 1 ● 2  Draft Issue  No. 7 
        Date of Issue: December  2022  
Sheet  2 of 5 
 
g. a flushing cistern designed to give flushes of different volumes - 
i. shall have a readily discernible method of actuating the flush of 
different volumes; and  
ii. shall have instructions, clearly and permanently marked on the 
cistern or displayed nearby, for operating it to obtain the different volumes of flush;  
h. every flushing ciste rn, not being a pressure flushing cistern or a urinal 
cistern, shall be fitted with a warning pipe or with a no less effective device;  
i. every urinal that is cleared by water after use shall be supplied with water from a flushing device which-  
i. in the case of  a flushing cistern, is filled at a rate suitable for the 
installation;  
ii. in all cases, is designed or adapted to supply no more water than is necessary for effective flow over the internal surface of the urinal and for replacement of the fluid in the trap; and 
j. except in the case of a urinal which is flushed manually, or which is flushed automatically by electronic means after use, every pipe which 
supplies water to a flushing cistern or trough used for flushing a urinal shall be fitted with an isolating valv e controlled by a time switch and a 
lockable isolating valve, or with some other equally effective automatic device for regulating the periods during which the cistern may fill.  
(2) Every water closet, and every flushing device designed for use with a wate r 
closet, shall comply with a specification approved by the regulator for the purposes of this Schedule.  
(3) The requirements of sub- paragraphs (1) and (2) do not apply where faeces 
or urine are disposed of through an appliance that does not solely use fluid to remove the contents.  
(4) The requirement  in sub -paragraph (1)(i) shall be deemed to be satisfied - 
a) in the case  of an automatically operated flushing cistern servicing urinals 
which is filled with water at a rate not exceeding-  
i. 10 litres per hour for a cistern serving a single urinal;  
ii. 7.5 litres per hour per urinal bowl or stall, or, as the case may be, for each 700 mm width of urinal slab, for a cistern serving two or 
more urinals;  Test Code Sheet  1 5 1 1 ● 2  Draft Issue  No. 7 
        Date of Issue: December  2022  
Sheet  3 of 5 
 
b) in the case of a manually or automatically operated pressure flushing 
valve used for flushing urinals which delivers not more than 1.5 litres per 
bowl or position each time the device is operated.  
(5) Until 1st January 2001 paragraphs (1)(a) and (d) shall have effect as if they 
provided as follows - 
a) “every  water closet pan shall be supplied with water from a flushing cistern 
or trough of the valveless type which incorporates siphonic apparatus; ” 
b) “no flushing device installed for use with a WC pan shall give a single flush 
exceeding 7.5 litres; ”. 
(6) Notwithstanding sub- paragraph 1(d), a flushing cistern installed before 1st 
July 1999 may be replaced by a cistern which delivers a similar volume and 
which may be either single flush or dual flush; but a single flush cistern may not be so replaced by a double flush cistern.  
(7) In this paragraph-  
 “pressure flushing  cistern ” means a WC flushing device that utilises the 
pressure of water within the cistern supply pipe to compress air and increase the pressure of water available for flushing a WC pan;  
 “pressure flushing valve”  means a self -closing valve supplied with water 
directly  from a supply pipe or a distributing pipe which when activated will 
discharge a pre -determined flush volume;  
 “trap” means a pipe fitting, or part of a sanitary appliance, that retains liquid 
to prev ent the passage of foul air; and  
 “warning pipe”  means an overflow pipe whose outlet is located in a position 
where the discharge of water can be readily seen.  
4. BRITISH STANDARDS OR WATER SPECIFICATION, DEEMED TO 
SATISFY WATER REGULATIONS  
REQUIREMENTS  
4.1 None. 
5. GENERAL T OLERANCES AND MEASUREMENTS  
In the absence of specific tolerances or accuracies the general tolerances and 
measurements set out in the WC Suite Performance Specifications shall apply.  
 Test Code Sheet  1 5 1 1 ● 2  Draft Issue  No. 7 
        Date of Issue: December  2022  
Sheet  4 of 5 
 
6. TEST PROCEDURE  
6.1 Tests are applicable to the following fittings:  
WC FLUSHING CISTERNS, which require to be tested to the regulator’s specification  
(A) WC FLUSHING CISTERNS, WHICH REQUIRE TO BE TESTED 
TO THE REGULATORS SPECIFICATION 
Apparatus  
a) Cistern, complete with fitments including flushpipe and cov er, installed in 
accordance with the manufacturer's instructions on a firm, flat, vertical surface.  
b) calibrated measuring container  
c) fluid level sensing devices  
d) electronic timer  
e) water supply controlled by a stopvalve  
f) power supply  
Procedure  
Assemble the ciste rn with its fitments supplied by the manufacturer, as described in 
the manufacturer’s instructions. Fasten the cistern by its normal fixing devices to a 
solid background.  
For high level cisterns, connect a back wall flush pipe having a internal diameter equal 
to the diameter of the outlet discharge valve and overall length of the minimum 
supplied by the manufacturer, with an engagement length of 50 mm maximum.  
For low level and close coupled cisterns connect a flush pipe into the outlet valve having an internal diameter equal to the diameter of the outlet discharge valve and overall length of the minimum supplied by the manufacturer, with an engagement 
length of  50 mm maximum.  
Set the dual -flush controller or setting if provided to the full -flush volume in accordance 
with the manufacturer's instructions. Connect the water supply to the flushing cistern that is controlled by a stop valve and fitted, if necessary w ith a pressure regulating 
valve to give a static pressure of 3 ±0.5 bar at the inlet to the cistern float operated valve. Adjust the float operated valve so that the valve closes when the water level reaches the marked water line of the cistern operate the cistern at least once prior to 
carrying out the test. Fill the cistern to the marked water line, shut off the water supply, unless essential for the normal operation of the flushing device.  
NOTE. Where a water supply is essential for the normal operation of the device, 
maintain the supply at a hydraulic pressure of 1.5 ±0.1 bar or the minimum required to operate the device, whichever is the greater.  Test Code Sheet  1 5 1 1 ● 2  Draft Issue  No. 7 
        Date of Issue: December  2022  
Sheet  5 of 5 
 
Operate the flushing device completing one flushing cycle. On completion of the flush, 
using the calibrated measuring container or calibrated weigh scales or platform, add 
0.5 litres of water to the cistern. Locate and position a fluid sensing device at the water level in the cistern. Using the calibrated measuring container add further water to the cistern equi valent to the volume of full flush less 1.0 litres. Locate and position a 
second fluid sensing device at the water level in the cistern. Add further water to the cistern up to the marked water level for the full flush volume. Connect the two fluid level se nsing devices to the electronic timer and connect to the power supply. Operate 
the flushing device and on completion of the flush record the time taken to discharge the volume of water between the fluid level sensing devices as displayed on the timer. 
Repeat the procedure a further four times.  
If the flushing device is provided with a reduced flush facility shut off the water and 
power supplies, and operate the flushing (full flush) mechanism. Using the calibrated 
container, add to the cistern a volume of w ater equivalent to the difference between 
the full flush volume and reduced flush volume as recorded. Add a further 0.5 litres. Locate and position a fluid level sensing device at the water level in the cistern. Using the calibrated measuring container or calibrated weigh scales or platform, add further water to the cistern until it is filled to a volume equivalent to the volume of full flush recorded less 1.0 litres. Locate and position a second fluid sensing device at this water 
level in the cistern. Add further water to the cistern, up to the marked water level for 
the full flush volume recorded. Turn on the power suppl y. Set the dual -flush controller 
or setting to the reduced- flush volume in accordance with the manufacturer's 
instructions. Operate the fl ushing device and on completion of the flush record the 
time taken to discharge the volume of water between the fluid level sensing devices as displayed on the timer. Repeat the procedure a further four times.  
Expression of results  
From the five recorded t imes, at each flush volume, determine the average time and, 
using the following formula, calculate the mean rate of discharge using the following methods.  
For the full flush  
𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉  𝑉𝑉𝑜𝑜 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑ℎ𝑎𝑎𝑎𝑎𝑎𝑎𝑉𝑉 𝑝𝑝𝑉𝑉𝑎𝑎  𝑜𝑜𝑉𝑉𝑉𝑉𝑉𝑉  𝑜𝑜𝑉𝑉𝑉𝑉𝑑𝑑ℎ 𝑑𝑑𝑖𝑖 𝑉𝑉𝑑𝑑𝑙𝑙𝑎𝑎𝑉𝑉𝑑𝑑−1.0 𝑉𝑉𝑑𝑑𝑙𝑙𝑎𝑎𝑉𝑉𝑑𝑑
𝐴𝐴𝐴𝐴𝑉𝑉𝑎𝑎𝑎𝑎𝑎𝑎𝑉𝑉 𝑙𝑙𝑑𝑑𝑉𝑉𝑉𝑉  𝑑𝑑𝑖𝑖 𝑑𝑑𝑉𝑉𝑑𝑑𝑉𝑉𝑖𝑖𝑑𝑑𝑑𝑑
 
For the reduced flush  
𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉  𝑉𝑉𝑜𝑜 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑ℎ𝑎𝑎𝑎𝑎𝑎𝑎𝑉𝑉 𝑝𝑝𝑉𝑉𝑎𝑎  𝑎𝑎𝑉𝑉𝑑𝑑𝑉𝑉𝑑𝑑𝑉𝑉𝑑𝑑  𝑜𝑜𝑉𝑉𝑉𝑉𝑑𝑑ℎ 𝑑𝑑𝑖𝑖 𝑉𝑉𝑑𝑑𝑙𝑙𝑎𝑎𝑉𝑉𝑑𝑑−1.5 𝑉𝑉𝑑𝑑𝑙𝑙𝑎𝑎𝑉𝑉𝑑𝑑
𝐴𝐴𝐴𝐴𝑉𝑉𝑎𝑎𝑎𝑎𝑎𝑎𝑉𝑉 𝑙𝑙𝑑𝑑𝑉𝑉𝑉𝑉  𝑑𝑑𝑖𝑖 𝑑𝑑𝑉𝑉𝑑𝑑𝑉𝑉𝑖𝑖𝑑𝑑𝑑𝑑 
7. ACCEPTANCE CRITERIA  
When tested as described above, the mean flush rate of discharge per flush shall be ≥  
1.85 L/s for full flush and ≥  1.6 L/s for reduced flush -  if provided.    
 
Test Code Sheet 1512.12 Wash of bowl  
    
Test Code Sheet  1 5 1 2 ● 12  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  1 of 5 
 
1. PURPOSE 
Water Closet Suite: Wash of Bowl verification as described in WC Suite Performance 
Specifications . 
2. TYPE OF TEST(S) - 
Wash of bowl.  
3. REGULATION REQUIREMENTS FOR FITTINGS.  
Schedule 2 
25. (1) Subject to the following provisions of this paragraph-  
a. every water closet pan shall be supplied with water from a flushing 
cistern, pressure flushing cistern or pressure flushing valve, and shall be so made and installed that after normal use its contents can be cleared effectivel y by a single flush of water, or, where the installation is designed 
to receive flushes of different volumes, by the largest of those flushes;  
b. no pressure flushing valve shall be installed-  
i. in a house, or  
ii. in any building not being a house where a minimum f low rate of 1.2 
litres per second cannot be achieved at the appliance;  
c. where a pressure flushing valve is connected to a supply pipe or distributing pipe, the flushing arrangement shall incorporate a backflow prevention device consisting of a permanently v ented pipe interrupter 
located not less than 300mm above the spillover level of the WC pan or  
urinal:  
d. no flushing device installed for use with a WC pan shall give a single 
flush exceeding 6 litres;  
e. no flushing device designed to give flushes of different volumes shall have a lesser flush exceeding two- thirds of the largest flush volume;  
f. every flushing cis tern, other than a pressure flushing cistern, shall be 
clearly marked internally with an indelible line to show the intended volume of flush, together with an indication of that volume;  Test Code Sheet  1 5 1 2 ● 12  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  2 of 5 
 
g. a flushing cistern designed to give flushes of different volumes - 
i. shall have a readily discernible method of actuating the flush of 
different volumes; and  
ii. shall have instructions, clearly and permanently marked on the 
cistern or displayed nearby, for operating it to obtain the different volumes of flush;  
h. every flushing ciste rn, not being a pressure flushing cistern or a urinal 
cistern, shall be fitted with a warning pipe or with a no less effective device;  
i. every urinal that is cleared by water after use shall be supplied with water from a flushing device which-  
i. in the case of  a flushing cistern, is filled at a rate suitable for the 
installation;  
ii. in all cases, is designed or adapted to supply no more water than is necessary for effective flow over the internal surface of the urinal and for replacement of the fluid in the trap; and 
j. except in the case of a urinal which is flushed manually, or which is flushed automatically by electronic means after use, every pipe which 
supplies water to a flushing cistern or trough used for flushing a urinal shall be fitted with an isolating valv e controlled by a time switch and a 
lockable isolating valve, or with some other equally effective automatic device for regulating the periods during which the cistern may fill.  
(2) Every water closet, and every flushing device designed for use with a wate r 
closet, shall comply with a specification approved by the regulator for the purposes of this Schedule.  
(3) The requirements of sub- paragraphs (1) and (2) do not apply where faeces 
or urine are disposed of through an appliance that does not solely use fluid to remove the contents.  
(4) The requirement  in sub -paragraph (1)(i) shall be deemed to be satisfied - 
a) in the case  of an automatically operated flushing cistern servicing urinals 
which is filled with water at a rate not exceeding-  
i. 10 litres per hour for a cistern serving a single urinal;  
ii. 7.5 litres per hour per urinal bowl or stall, or, as the case may be, for each 700 mm width of urinal slab, for a cistern serving two or 
more urinals;  Test Code Sheet  1 5 1 2 ● 12  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  3 of 5 
 
b) in the case of a manually or automatically operated pressure flushing 
valve used for flushing urinals which delivers not more than 1.5 litres per 
bowl or position each time the device is operated.  
(5) Until 1st January 2001 paragraphs (1)(a) and (d) shall have effect as if they 
provided as follows - 
a) “every  water closet pan shall be supplied with water from a flushing cistern 
or trough of the valveless type which incorporates siphonic apparatus; ” 
b) “no flushing device installed for use with a WC pan shall give a single flush 
exceeding 7.5 litres; ”. 
(6) Notwithstanding sub- paragraph 1(d), a flushing cistern installed before 1st 
July 1999 may be replaced by a cistern which delivers a similar volume and 
which may be either single flush or dual flush; but a single flush cistern may not be so replaced by a double flush cistern.  
(7) In this paragraph-  
 “pressure flushing  cistern ” means a WC flushing device that utilises the 
pressure of water within the cistern supply pipe to compress air and increase the pressure of water available for flushing a WC pan;  
 “pressure flushing valve”  means a self -closing valve supplied with water 
directly  from a supply pipe or a distributing pipe which when activated will 
discharge a pre -determined flush volume;  
 “trap” means a pipe fitting, or part of a sanitary appliance, that retains liquid 
to prevent the passage of foul air; and  
 “warning pipe”  means an overflow pipe whose outlet is located in a position 
where the discharge of water can be readily seen.  
4. BRITISH STANDARD OR WATER SPECIFICATION DEEMED TO 
SATISFY WATER REGULATI ONS  REQUIREMENTS.  
4.1 None.  
5. GENERAL T OLERANCES AND MEASUREMENTS  
In the absence of specific tolerances or accuracies the general tolerances and 
measurements set out in the WC Suite Performance Specifications shall apply . 
6. TEST PROCEDURE.  
Note: Unless stated otherwise the temperature of the test fluid shall be 20 ±10ºC.  
6.1 Tests are applicable to the following fittings . Test Code Sheet  1 5 1 2 ● 12  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  4 of 5 
 
ALL WC CISTERNS AND PANS SUPPLIED AS SUITES, WHICH 
REQUIRE TO BE TESTED TO THE REGULATORS SPECIFICATION  
(A) ALL WC CISTERNS AND PANS SUPPLIED AS SUITES, WHICH 
REQUIRE TO BE TESTED TO THE REGULATORS SPECIFICATION.  
6.2 Apparatus  
a) WC pan with associated flushing cistern and/or flushing device, or a close 
coupled/one- piece suite, all meeting the appropriate requirements of this standard, 
installed in accordance with the manufacturer's instructions on a firm, flat  
horizontal/vertical surface as appropriate. The flushing device shall satisfy the requirements of this specification.  
b) supply of fine dry wooden sawdust;  
c) 2 mm grade sieve;  
d) water supply.  
6.3 Procedure  
Set the dual -flush controller or setting if provided to the full -flush volume in accordance 
with the manufacturer's instructions.  
Fill any cistern to the marked water level. Shut off the water supply, unless essential 
for the normal oper ation of the flushing device.  
NOTE: Where a water supply is essential for the normal operation of the device, 
maintain the supply at a hydraulic pressure of (1.5 ±0.1) bar or the minimum required 
to operate the device, whichever is the greater.  
Moisten the complete inner surface of the WC pan to be tested. Immediately 
afterwards, sprinkle 20 g of sieved sawdust as completely and evenly as possible over 
the moistened surface. Operate the flushing device measure and record any area of 
unflushed sur face.  
Repeat the procedure a further four times.  
NOTE: In the case of a bowl with a rim, the surface to be tested is below the flushing 
rim and above the water in the trap. In the case of a rimless bowl, the surface to be tested is the area between a hori zontal line 85 mm below the top edge of the WC pan 
and above the water in the trap.  
6.4 Expression of results  
On completion of the five test procedures calculate the arithmetic average of the unflushed area between the water level in the trap and the underside of the rim. 
Record compliance, or any failure to comply with the acceptance criteria.  
 Test Code Sheet  1 5 1 2 ● 12  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  5 of 5 
 
7. ACCEPTANCE CRITERIA  
When tested as described above, the arithmetic average of any unflushed area below 
the rim and above the surface of the trap shall be no greater than 50 cm2 after the five 
flushing operations.    
 
Test Code Sheet 1611.16 Liquid contaminant, 
dye retention  
    
Test Code Sheet  1 6 1 1 ● 16  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  1 of 5 
 
1. PURPOSE 
Water Closet Suite: Liquid contaminant dye retention verification as described in WC 
Suite Performance Specifications . 
2. TYPE OF TEST(S)  
Liquid contaminant, dye retention.  
3. REGULATION REQUIREMENTS FOR FITTINGS.  
Schedule 2 
25. (1) Subject to the following provisions of this paragraph-  
a. every water closet pan shall be supplied with water from a flushing 
cistern, pressure flushing cistern or pressure flushing valve, and shall be so made and installed that after normal use its contents can be cleared 
effectively by a single flush of water, or, where the installation is designed 
to receive flushes of different volumes, by the largest of those flushes;  
b. no pressure flushing valve shall be installed-  
(i) in a house, or  
(ii) in any building not being a house where a minimum flow rate of 1.2 litres per second cannot be achieved at the appliance;  
c. where a pressure flushing valve is connected to a supply pipe or distributing pipe, the flushing arrangement shall incorporate a backflow prevention device consisting of a permanently vented pipe interrupter 
located not less than 300mm above the spillover level of the WC pan or  
urinal:  
d. no flushing device installed for use with a WC pan shall give a single 
flush exceeding 6 litres;  
e. no flushing device designed to give flushes of different volumes shall have a lesser flush exceeding two- thirds of the largest flush volume;  
f. every flushing cistern, other than a pressure flushing cistern, shall be clearly marked internally with an indelible line to show the intended volume of flush, together with an indication of that volume;  Test Code Sheet  1 6 1 1 ● 16  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  2 of 5 
 
g. a flushing cistern designed to give flushes of different volumes - 
(i) shall have a readily discernible method of actuating the flush of 
different volumes; and  
(ii) shall have instructions, clearly and permanently marked on the 
cistern or displayed nearby, for operating it to obtain the different 
volumes of flush;  
h. every flushing cistern, not being a pressure flushing cistern or a urinal 
cistern, shall be fitted with a warning pipe or with a no less effective 
device;  
i. every urinal that is cleared by water after use shall be supplied with water 
from a flushing device which-  
(i) in the case of a flushing cistern, is filled at a rate suitable for the installation;  
(ii) in all cases, is designed or adapted to supply  no more water than is 
necessary for effective flow over the internal surface of the urinal and 
for replacement of the fluid in the trap; and  
j. except in the case of a urinal which is flushed manually, or which is 
flushed automatically by electronic means af ter use, every pipe which 
supplies water to a flushing cistern or trough used for flushing a urinal 
shall be fitted with an isolating valve controlled by a time switch and a 
lockable isolating valve, or with some other equally effective automatic device for regulating the periods during which the cistern may fill.  
(2) Every water closet, and every flushing device designed for use with a water closet, shall comply with a specification approved by the regulator for the purposes of this Schedule.  
(3) The requi rements of sub- paragraphs (1) and (2) do not apply where faeces 
or urine are disposed of through an appliance that does not solely use fluid to remove the contents.  
(4) The requirement  in sub -paragraph (1)(i) shall be deemed to be satisfied - 
a. in the case  of an automatically operated flushing cistern servicing urinals 
which is filled with water at a rate not exceeding-  
(i) 10 litres per hour for a cistern serving a single urinal;  
(ii) 7.5 litres per hour per urinal bowl or stall, or, as the case may be, for each 700 mm width of urinal slab, for a cistern serving two or 
more urinals;  Test Code Sheet  1 6 1 1 ● 16  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  3 of 5 
 
b. in the case of a manually or automatically operated pressure flushing 
valve used for flushing urinals which delivers not more than 1.5 litres per 
bowl or position each time the device is operated.  
(5) Until 1st January 2001 paragraphs (1)(a) and (d) shall have effect as if they provided as follows - 
a. “every  water closet pan shall be supplied with water from a flushing cistern 
or trough of the valveless type which incorporates siphonic apparatus; ” 
b. “no flushing device installed for use with a WC pan shall give a single flush 
exceeding 7.5 litres; ”. 
(6) Notwithstanding sub- paragraph 1(d), a flushing cistern installed before 1st 
July 1999 may be replaced by a cistern which delivers a similar volume and 
which may be either single flush or dual flush; but a single flush cistern may not be so replaced by a double flush cistern.  
(7) In this paragraph-  
 “pressure flushing  cistern ” means a WC flushing device that utilises the 
pressure of water within the cistern supply pipe to compress air and increase 
the pressure of water available for flushing a WC pan;  
 “pressure flushing valve”  means a self -closing valve supplied with water 
directly from a supply pipe or a distributing pipe which when activated will 
discharge a pre -determined flush volume;  
 “trap” means a pipe fitting, or part of a sanitary appliance, that retains liquid 
to prevent the passage of foul air; and  
 “warning pipe”  means an overflow pipe whose outlet is located in a position 
where the discharge of water can be readily seen.  
4. BRITISH STANDARD OR WATER SPECIFICATION DEEMED TO 
SATISFY WATER REGULATIONS  REQUIREMENTS.  
4.1 None.  
5. GENERAL T OLERANCES AND MEASUREMENTS  
In the absence of specific tolerances or accuracies the general tolerances and 
measurements set out in the WC Suite Performance Specifications shall apply . 
6. TEST PROCEDURE  
Note: Unless stated otherwise the temperature of the test fluid shall be 20 ±10ºC.  
6.1 Tests are  applicable to the following fittings:  Test Code Sheet  1 6 1 1 ● 16  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  4 of 5 
 
ALL WC CISTERNS AND PANS SUPPLIED AS SUITES, which require to be tested to 
the regulators specification.  
(A) ALL WC CISTERNS AND PANS SUPPLIED AS SUITES, WHICH 
REQUIRE TO BE TESTED TO THE REGULATORS SPECIFICATION.  
6.2 Apparatus  
a) WC pan with associated flushing cistern and/or flushing device, or a close 
coupled/one- piece suite, all meeting the appropriate requirements of this 
standard, installed in accordance with the manufacturer's instructions on a firm, 
flat horizontal/vertical surface as appropriate. The flushing device and cistern 
shall satisfy the requirements of this  specification.  
b) liquid contaminant dye (5 g of potassium permanganate per litre of water);  
WARNING: Potassium permanganate is an oxidant and appropriat e 
precautions should be taken when preparing the solution.  
c) calibrated spectrophotometer or opacity meter with cuvette:  
d) fluid suction device;  
e) water supply.  
6.3 Procedure  
Set the dual -flush controller or setting -  if provided -  to the full -flush volume in 
accordance with the manufacturer's  instructions. Fill any cistern to the marked water 
level. Shut off the water supply, unless essential for the normal operation of the 
flushing device.  
Note. Where a water supply is essential for the normal operation of the device, maintain the supply at a hydraulic pressure of (1.5 ±0.1) bar or the minimum required 
to operate the device, whichever is the greater.  
Using the fluid suction device, remove any water from the WC's trap. Measure the 
opacity through the 5 g of potassium permanganate per litre of water dye solution 
(Stock solution). Record the result. Fill the WC's trap with liquid contaminant dye to the 
trap seal depth. Operate the flushing device. On completion of the flush, stir the 
remaining liquid to a uniform concentration. In a time ≤ 10 seconds after stirring has 
stopped, draw and place a sample of the liquid remaining in the trap in the cuvette. 
Meas ure and record the concentration of potassium permanganate in the sample. 
Calculate its percentage dilution against the stock solution Repeat the procedure a 
further 4 (9) times as appropriate (see acceptance criteria) . 
Reset the dual -flush control or setti ng - if provided -  to reduced- flush volume and 
repeat the above procedure 5 (10) times  as appropriate at the reduced flush volume.  
 Test Code Sheet  1 6 1 1 ● 16  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  5 of 5 
 
6.4 Expression of results  
Record compliance, or failure to comply with the requirements of the acceptance 
criteria.  
7. ACCEPTANCE  CRITERIA  
When tested as described above, for the first five flush cycles, or for a minimum of 
nine out of ten flush cycles at full flush volume, the contaminate level shall be ≤1 %. 
For the first five flush cycles, or for a minimum of nine out of ten flus h cycles at 
reduced flush volume when provided, the contaminate level shall be ≤6 %.    
 
Test Code Sheet 2212.3 Type AG –  Vacuum / 
Dimensional  
    
Test Code Sheet  2 2 1 2 ● 3  Draft Issue  No. 5 
        Date of Issue: December  2022  
Sheet  1 of 8 
 
1. PURPOSE 
Type AG air gap arrangement verification as described in the Specification for the 
Prevention of Backflow . 
2. TYPE OF TEST(S)  
Vacuum / Dimensional  
3. WATER REGULATIONS REQUIREMENTS FOR FITTINGS  
Schedule 2  
15-(1) …. every water system shall contain an adequate device or devices for 
preventing backflow of fluid from any appliance, fitting or process from 
occurring.  
4. BRITISH STANDARDS OR WATER SPECIFICATION, DEEMED TO 
SATISFY WATER REGULATIONS  
REQUIREMENTS  
4.1 None.  
5. GENERAL T OLERANCES AND MEASUREMENTS 
In the absence of specific tolerances or accuracies the following shall apply.  
1. Dimension : up to and including 75 mm ±5% ; over 75 mm ±2% . 
2. Flow rate and pressure: ± 5 % of the value specified.  
3. Temperature:  cold water ± 10 °C of the value specified.  
4. Linear measuring instruments shall have a minimum resolution of 0. 5 mm. 
5. Timing instruments shall have a minimum resolution of 0. 1 seconds . 
6. All the measuring instruments shall have an error limit of ±2 % of the measured 
value.  
6. TEST PROCEDURE  
Note  1: Unless otherwise stated the temperature of the test fluid shall be 20 ± 10°C  Test Code Sheet  2 2 1 2 ● 3  Draft Issue No. 5 
        Date of Issue: December  2022  
Sheet 2 of 8 
 
6.1 Tests applicable to the following: - 
(A) TYPE AG AIR GAPS  
TEST METHOD  
i. SCOPE  
This procedure specifies the characteristics of type AG air gaps, verified by 
measurement or by vacuum test. Air gaps that  comply with the requirements of this 
procedure are devices for protection of potable water installations from pollution. In  
addition to factory assembled products this procedure includes requirements for site constructed air gaps.  
This is a performance standard for 'AG' air gaps. Materials of construction must be fit 
for the purpose and application to ensure compliance with this procedure during 
normal working use.  
ii. DEFINITIONS  
For the purpose of this procedure the following definitions apply.  
ii.i Air Gap(s) Family A Type G  
The AG device is an air gap placed permanently and vertically between the lowest point of the feed orifice and the critical  water level.  
The overflow shall be capable of draining the maximum inflow of water in a positive 
pressure fault condition.  
ii.ii Spillover Level  
The level at which water will start to overflow the receiving vessel, with all outlets 
closed.  
ii.iii Maximum Level  
The highest water level reached above the spillover level under positive fault 
conditions, with all outlets closed.  
ii.iv Critical Water Level  
The level (h) above the spill over level two seconds after the maximum water flow has ceased. (The height between the spillover level and the critical level is dimension ‘ h’). Test Code Sheet  2 2 1 2 ● 3  Draft Issue No. 5 
        Date of Issue: December  2022  
Sheet 3 of 8 
 
ii.v Internal Diameter ‘D’ of Feed Pipe (Bore)  
Diameter ‘D’ (mm) is the maximum internal diameter found within the last metre of the 
supply pipe or the DN of the inlet  connection.  
ii.vi Graphic Symbol  
 
iii. DESIGNATION  
The air gap is designated by:  
• the reference to this standard.  
• its Family, its Type.  
• the DN of the feed pipe to the assembly.  
iv. MATERIALS  
iv.i Materials choice  
The manufacturer shall state the type of materials chosen in his technical and commercial documents.  
The surface condition of materials  in contact with water shall be chosen to be the least 
inclined to scale.  
The materials used upstream, and including the atmospheric outlet opening, must comply with  BS 6920 or other national standard which provides an equivalent level of 
protection  or performance.  
The choice of other material is discretionary but shall be suitable for the intended use 
of the appliance (temperature,  corrosion, scale, etc).  
There are no special requirements concerning the materials downstream of the 
atmospheric outlet opening provided they  do not have any harmful effect on the 
upstream part.  
Test Code Sheet  2 2 1 2 ● 3  Draft Issue No. 5 
        Date of Issue: December  2022  
Sheet 4 of 8 
 
v. DESIGN  
v.i General  
The protection assembly comprises four parts integral with one another:  
• a water inlet device.  
• a receiving vessel.  
• an overflow.  
• air break to drain.  
v.ii Water Inlet Device  
v.ii.i Every float -operated valve or other device which controls the inflow of water to a 
receiving vessel shall be securely and rigidly fixed to that vessel.  
v.ii.ii Every feed ;pipe supplying water to such a valve assembly or other device shall be 
fixed in its position to prevent it from  moving or buckling, (i.e. bending or deformation 
of the assembly).  
v.ii.iii Submerged supply pipes to the inlet device that have joints which are adjustable or 
can be dismantled, are not permitted below the c ritical water level (h).  
v.ii.iv  The discharge outlet of the inlet device shall not come into contact in any way with a 
product from  downstream at the maximum water level.  
v.iii Overflow Arrangements  
v.iii.i The overflow shall be capable of draining off the maximum inlet flow.  
v.iii.ii Shall not be less than 19mm internal diameter.  
v.iii.iii Overflow arrangements must include an air break prior to a connection to drain. An air break to drain must conform to Test Code Sheet 2212.10 or BS EN  1717 
requirements . 
NOTE 2: The length of the overflow before the air break to drain must not be of such a 
length that it will cause air gap ‘AG’ to be violated. All air gaps to drain arrangements 
shall be visible.  
NOTE 3: Clauses A5.1 v.iii.ii and A5.1  v.iii.iii do not apply to a WC suite where the 
overflow discharges internal to the WC bowl providing the overflow is not less than 19 
mm internal diameter at the point water enters the overflow to be discharged; and the critical water level (h) has been verified by test.  
 Test Code Sheet  2 2 1 2 ● 3  Draft Issue No. 5 
        Date of Issue: December  2022  
Sheet 5 of 8 
 
7. ACCEPTANCE CRITERIA  
7.1 Air Gap Distance  
For air gaps 'AG' the critical water level shall be established and the air gap distance 
measured from the lowest point of the water inlet to the critical water level (see 
informative Annex B) or by vacuum test (see Annex A).  
Air gaps 'AG' must be greater than 2D and never less than 20mm or must meet the requirements of the vacuum test  specified in Annex A.  
7.2 Test Procedure  
The overflow  
(a) The overflow shall be verified by a 2mm deep 19mm diameter plug or no less effective method.  
The air gap ‘AG’ is determined by either: - 
(b) Measurement by test -  ‘h’ is determined by measurement of the depth of water 
above the spillover level of the  overflow two seconds after the inflows equal to Q = 
0.14D
2 in litres per minute has stopped, or a dynamic pressure of 10 bar has 
stopped if the flow rate Q cannot be achieved, where ‘D’ is the bore inlet (see ii.v) and with all outlets closed,  based on a velocity of  3 m/s.  
NOTE  4: The receiving vessel must be fitted with a warning / overflow pipe.  
NOTE  5: There is no relationship between the maximum fault level and the top 
most level of the warning overflow pipe.  
(c) Vacuum Test  
The body of the inlet valve must satisfy the vacuum test specification in Annex A.  
Air Gap –  Vacuum test  
 
1 = Warning/Overflow Pipe  5 = Internal Diameter of Feed Pipe (Bore)  
2 = Air Gap (AG)  7 = Spill- over Level  
3 = Feed Pipe  8 = Critical Water Level (h)  
4 = Feed Orifice  9 = Maximum Water Level   
Test Code Sheet  2 2 1 2 ● 3  Draft Issue No. 5 
        Date of Issue: December  2022  
Sheet 6 of 8 
 
ANNEX A 
TITLE: WORKING PAPER FOR METHOD OF VACUUM TEST  
1. SCOPE 
This annex describes the apparatus and a method for applying a vacuum test to 
backflow prevention devices and water  using appliances to determine that they have 
an acceptable degree of protection against backflow or backsiphonage.  
2. DEFINITIONS  
2.1 Critic al level: The highest level of the fluid reached in any part of the appliance 2 
seconds after closing water inlet  starting from maximum fluid level.  
In a pressurised system this is the maximum manometric height allowed.  
3. APPARATUS  
3.1 General  
The test apparatus shall be arranged and constructed so that the absolute pressure 
measured near the appliance under test  on its supply side remains less than 50 KPa ( -
50 KPa gauge pressure) for at least 5 seconds.  
3.2 Vacuum vessel and connecting pipework, of  sufficient strength to support a total 
vacuum. The vacuum vessel shall be provided with a drain cock to remove any water 
drawn into the vessel during the test.  
NOTE  6: Recommended capacities of the vacuum vessel are given in Table 1.  
3.3 Vacuum device, capable of reducing the absolute pressure within the vacuum vessel 
to 20 KPa ( -80 KPa gauge pressure).  
3.4 Pipes and fittings, of nominal size not less than that of the appliance under test.  
Any valve or fitting installed in the test pipe shall be a full -way valve offering an 
unimpeded flow path.  
Connections to the vacuum vessel shall not unduly impede the fluid flow and shall 
have a low loss profile when very low  resistance appliances are tested.  
3.5 Vacuum gauges. from 100 KPa absolute to 10 KPa absolute, w ith an accuracy of 2 % 
of the reading. The system  connection shall be made in such a way that it does not 
disturb the flow in the pipework.  
3.6 Water trap, provided with a cock to allow the trapped water to be drained. The trap shall not so restrict the fl ow that the  requirement of 4.1 cannot be met.  Test Code Sheet  2 2 1 2 ● 3  Draft Issue No. 5 
        Date of Issue: December  2022  
Sheet 7 of 8 
 
4.  PROCEDURE  
4.1 Remove or render inoperative any upstream backflow prevention device.  
4.2 Connect the water inlet connection of the appliance under test to the test pipe.  
4.3 Maintain the critical water level  as established in 7 .2 (a). The critical level shall be 
maintained during the test by supply  from a separate source. This supply shall be 
submerged to prevent disturbance of the water surface.  
4.4 Close the full -way valve and the water trap drain valve.  
4.5 Evacuate the vacuum vessel to an absolute pressure of 20 KPa ( -80 KPa gauge 
pressure) as indicated by vacuum gauge A.  
4.6 Open the full -way valve within a period of 2 s.  
4.7 Read the vacuum gauge B. Check that the absolute pressure does not exceed 50 KPa 
(-50 KPa gauge pressure) for a period of at least 5 s after the full way valve is fully 
open.  
4.8 Observe the water trap.  
NOTE  7: If the receiving vessel can be subject to positive pressure backflow, it is 
important that the inlet orifice is  positioned so that it cannot be contaminated by the 
ascending / returning fluid.  
Figur e 1: Arrangement of apparatus for vacuum test  
 
Drawing is diagrammatic only  
KEY.  
1 Vacuum pump  4 Full -way valve  
2 Vacuum gauge A  5 Vacuum gauge B  
3 Vacuum vessel  6 5 DN to 10 DN  32 5
64
1Test Code Sheet  2 2 1 2 ● 3  Draft Issue No. 5 
        Date of Issue: December  2022  
Sheet 8 of 8 
 
5.  ACCEPTANCE CRITERIA  
No water shall be collected in the water trap.  
Table 1 : Recommended vacuum vessel capacities  
Nominal size of appliance inlet 
connection  
(mm)  Recommended minimum capacity of 
vacuum vessel  
(m3) 
≤ 22 
> 22 <  ≤ 54 
> 54 <  ≤ 76.1  
> 76.1 ≤ 108 
> 108  ≤ 159 0.25 
0.75 
2 
4 
7 
NOTE  8: Actual vacuum vessel capacity is also dependent upon the backflow 
prevention device being tested.  
   
 
Test Code Sheet 2213.15 Type AC –  
Dimensional  
    
Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  1 of 10 
 
1. PURPOSE  
Type AC air gap arrangement verification as described in the Specification for the 
Prevention of Backflow.  
2. TYPE OF TEST(S)  
Dimensional  
3. WATER REGULATIONS REQUIREMENTS FOR FITTINGS  
Schedule 2  
15-(1) …every water system shall contain an adequate device or devices for 
preventing backflow of fluid from any  appliance, fitting or process from occurring.  
4. BRITISH STANDARDS OR WATER SPECIFICATION, DEEMED TO 
SATISFY WATER REGULATIONS  REQUIREMENTS  
4.1 None.  
5. GENERAL TOLERANCES AND MEASUREMENTS 
In the absence of specific tolerances or accuracies the following shall apply.  
1. Dimension : up to and including 75 mm ±5% ; over 75 mm ±2% . 
2. Flow rate and pressure: ± 5 % of the value specified.  
3. Temperature:  cold water ± 10 °C of the value specified.  
4. Linear measuring instruments shall have a minimum resolution of 0. 5 mm. 
5. Timing instruments shall have a minimum resolution of 0. 1 seconds . 
6. All the measuring instruments shall have an error limit of ±2 % of the measured 
value.  
6. TEST PROCEDURE  
6.1 Tests applicable to the following: - Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  2 of 10 
 
TYPE AC AIR GAP WITH SINGLE SUBMERGED FEED (INCORPORATING AIR 
INLET AND OVERFLOW)  
up to and including DN 250  
Devices for the prevention of contamination by backflow.  
(A) TYPE AC AIR GAP WITH SINGLE SUBMERGED FEED 
(INCORPORATING AIR INLET AND OVERFLOW)  
TEST METHOD  
i. SCOPE  
This procedure specifies the characteristics of type AC air gaps with submerged feed 
incorporating air inlet and an overflow from a container for inlet or feed pipes of 
nominal size up to and including DN 250. Air gaps that comply with the requirements 
of this procedure are devices for protection of potable water installations from pollution 
fluid risk 3. In  addition to factor y assembled products this procedure includes 
requirements for site constructed air gaps.  
The products specified are for single feed only and suitable for water temperatures up 
to and including 65°C and occasional temperatures up to and including 95°C. 
Howe ver in some instances the maximum operating temperature may  be limited to 
40°C and should be marked accordingly.  
ii. DEFINITIONS  
For the purpose of this procedure the following definitions apply.  
ii.i Air Gap family ‘A’ type AC -  Air gap with single submerged feed (incorporating 
air inlet and overflow)  
A non-mechanical form of backflow prevention air gap suitable for fluids only, no solids 
or sludges, placed permanently and vertically between the lowest point of the air inlet 
orifice in the feed pipe and critical water level at which the container overflows.  
ii.ii Spill- over Level  
The point at which the water first starts to overflow into the overflow pipe (invert).  Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  3 of 10 
 
ii.iii Critical Water Level  
The level (h) above the spill -over level two seconds after the inlet water has ceased to 
flow. 
ii.iv Graphic symbol  
Figure 1 Type AC graphic symbol  
 
iii. DESIGNATION  
The air gap family ‘A’ type AC is designated by the following:  
- the reference to this standard.  
- its Family, its Type.  
- the DN of the feed pipe.  
- example of the designation:  
- air gap Family A Type AC DN15 TSN AC- 01. 
iv. MATERIALS  
iv.i Materials choice  
The manufacturer shall state the type of materials chosen in his technical and 
commercial documents.  
The surface condition of materials in contact with water shall be chosen to be the least 
inclined to scale.  
The materials used upstream, and including the atmospheric outlet opening (i.e. the 
air port inlet) , must comply with  BS 6920 or other national standard which provides an 
equivalent level of protection or performance . 
The choice of other material is discretionary but shall be suitable for the intended use 
of the appliance (temperature,  corrosion, scale, etc).  Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  4 of 10 
 
There are no special requirements concerning the materials used downstream of the 
atmospheric outlet opening provided they do not have any harmful effect on the 
upstream part.  
v. DESIGN  
v.i General  
The protection assembly comprises three parts integral with one another:  
- a water inlet device.  
- a receiving vessel (container) with overflow.  
- a permanently open air port inlet.  
The air port inlet shall be above the invert of the overflow.  
The smallest dimension of the air inlet port shall not be less than 4 mm  and capable of 
accepting a pin gauge of  4 mm +0.1
−0 or a no less effective method.  
v.ii Water Inlet Device  
v.ii.i Every float -operated valve or other device which controls the inflow of water to a 
storage cistern shall be securely and rigidly fixed to that cistern.  
v.ii.ii Every feed pipe supplying water to such a valve or other device shall be fixed in its 
position to prevent it from moving or  buckling.  
v.ii.iii No mechanical joint (see Notes 1 and 2 ) within the cistern on submerged supply pipes 
or inlet devices are permitted at or below the critical water level (h).  
NOTE 1: Mech anical joints are joints which when undone open a direct pathway 
between the wholesome water (incoming supply) and the water stored within the 
flushing cistern. These include joints that are ‘adjustable’ or can be ‘dismantled’; rely 
on elastomeric, or othe r material, to provide a water -tight seal; or where the coupling 
of two components being dependent upon mechanically applied forces, with or without 
the use of secondary seal.  
NOTE 2: For the purposes of this specification the following are not considered 
mechanical joints . Nuts or jointing mechanism on the diaphragm housing assembly of 
the inlet device. Joints where the joining surface are permanently fused together e.g. 
by a chemical process or the application of heat.  Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  5 of 10 
 
v.iii Overflow Arrangements  
v.iii.i The overflow shall be capable of draining off the maximum inlet flow.  
v.iii.ii Shall not be less than 19 mm internal diameter.  
v.iii.iii Overflow arrangements must include an air break prior to a connection to drain. An air 
break to drain must conform to Test Code Sheet 2212.10 or BS EN 1717.  
NOTE  3: The length of the overflow before the air break to drain must not be of such a 
length that it will cause air gap ‘AC’ to be violated. All air gaps to drain arrangements 
shall be visible.  
NOTE 4 : Clauses v.iii.ii and v.iii.iii do not apply to a WC suite where the overflow 
discharges internal to the WC bowl  providing the overflow is not less than 19 mm 
internal diameter at the point water enters the overflow to be discharged ; and the 
critical water level (h ) has been verified by test.  
7. ACCEPTANCE CRITERIA  
7.1 DISTANCE OF AIR GAP (SEE FIGURE 2)  
The clearance ‘A’ measured between the lowest external point of the permanently 
open air port inlet and the critical water level shall be at least equal to twice the 
internal diameter of the inlet pipe and never less than 20 mm.   
7.1.1 Establishing critical water level ‘h’  
Dimension ‘h’ is determined by measurement of the depth of water above the spillover 
level of the overflow two seconds after the inflows equal to Q = 0.14D2 in litres per 
minute has stopped, or a dynamic pressure of 10 bar has stopped if the flow rate Q cannot be achieved, where ‘D’ is the bore inlet and with all outlets closed, based on a 
velocity of 3 m/s.  
Note 5: Diameter ‘D’ (mm) is the maximum in ternal diameter found within the last 
metre of the supply pipe or the DN of the inlet connection.  
7.1.2 Acceptance criteria  
A ≥ 2D but not less than 20 mm.  
7.2 OVERFLOW  
7.2.1  General  
The overflow shall be so designed as to be capable of providing an appropriate air gap 
between the lowest point of the air  port inlet and the critical water level, from a 
maximum water level caused by an inflow.  Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  6 of 10 
 
Figure 2 Air gap vacuum test  
 
Legend:  
A = Air Gap  E = Receiving Vessel  
B = Feed Pipe  F = Spill- over Level  
C = Feed Orifice  h = Critical Water Level (h)  
D = Internal Diameter of Feed Pipe  1 = Air Inlet  
7.2.2 Acceptance criteria  
The overflow is not less than 19 mm internal diameter.  
For internally discharging WC suite overflow s (see Note 4) using a 2 mm deep 19 mm 
diameter plug, or a no less effective method, the overflow is not less than 19 mm at 
the point where water enters the overflow . 
7.3 EFFICIENCY OF AIR PORT INLET  
7.3.1 Verify the air port is capable of accepting a pin gauge of  4 mm +0.1
−0, or a no less 
effective method, through its whole length.  
7.3.2 Remove or render inoperative any additional backflow prevention devices upstream or 
within the arrangement.  
Foul the inlet valve seat/diaphragm with a 0.75 mm nominal diameter wire, or 
otherwise no less effective method, which ensures the waterway through the seat 
remains open throughout the test.  
Apply the vacuum test (see Annex A) . 
7.3.3 Where document ed tests have been pe rformed and meet the acceptance criteria of 
TCS 2212.20, or an identical test  (e.g. BS 1212- 3:1990) , the vacuum test in 7 .3.2 is 
deemed to have been satisfied.  
 
Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  7 of 10 
 
7.3.4 Acceptance criteria  
The air port is ≥ 4 mm; and  
There is no visible evidence of backflow of water.  
  Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  8 of 10 
 
ANNEX A (INFORMATIVE)  
Vacuum test  
А.1 APPARATUS  
A.1.1  General  
The test apparatus shall be arranged and constructed (see Figure A1) so that the 
absolute pressure measured near the device under test on its supply side remains 
less than 50 kPa ( -50 kPa gauge pressure) for at least 5 s.  
NOTE  A1: These conditions indicate the existence of choking air flow. Details of the 
components are given in A1.3 to A1.5  
A.1.2  Vacuum vessel and connecting pipework, of sufficient strength to support a total vacuum safely. The vacuum vessel shall be provided with a drain cock to remove any 
water drawn into the vessel during the test.  
NOTE  A2: Recommended capacities of the vacuum vessel are given in T able A1. 
A.1.3  Vacuum device, capable of reducing the absolute pressure within the vacuum vessel 
to 20 kPa ( -80 kPa gauge pressure).  
A.1.4  Pipes and fittings, of nominal size not less than the bore of the orifice at the lowest 
part of the inlet or feed part of the device under test. If the air gap is not visi ble, the 
connecting pipework shall be of transparent material.  
Any valve fitted in the test pipe shall be a full -way valve offering an unimpeded flow 
path.  
The pipe length between the vacuum gauge to the device on test shall have a length of 5 DN to 10 DN.  
Connections to the vacuum vessel shall not unduly impede the fluid flow and shall 
have a low loss profile.  
A.1.5  Vacuum gauges, shall have an appropriate range i.e. 100 kPa to 0 kPa and an 
accuracy of 1 % test pressure. The gauge connection shall be made in such a way that it does not disturb the flow in the pipework.  
A.2 PROCEDURE  
A.2.1  Connect the fitting to be tested to the test apparatus.  
A.2.2  With all valves upstream of the air gap including the test valve fully open, establish 
and maintain the cr itical water level. The critical level shall be maintained during the 
test by supply from a separate source at the same flow rate as the maximum specified 
by the manufacturer. The discharge shall be submerged to prevent disturbance of the water surface.  Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  9 of 10 
 
A.2.3 Close the full -way valve.  
A.2.4  Evacuate the vacuum vessel to an absolute pressure of 20 kPa ( -80 kPa gauge 
pressure as indicated by vacuum gauge A (see Figure A1) . 
A.2.5 Open the full -way valve within a period of 2 s.  
A.2.6  Read the vacuum gauge B. Ch eck that the absolute pressure does not exceed 50 kPa 
(-50 kPa gauge pressure) for a period of at least 5 s after the full way valve is fully 
open.  
A.2.7  If the absolute pressure does not remain below 50 kPa ( -50 kPa gauge pressure) for 
at least 5 s reduce  the flow resistance of the connecting pipework by increasing the 
bore of the pipe between the vacuum gauge B and the vacuum vessel and/or by 
reducing its length.  
A.2.8  Observe the air gap if visible, or a transparent tube for evidence of backflow of water . 
A3 OPERATING CRITERIA  
A.3.1  If the conditions of choking flow are met (see A.1.1) the test is deemed to be valid.  
Table A1 : Recommended vacuum vessel capacities  
Bore of orifice at lowest part of 
inlet or feedpipe (mm)  Recommended minimum 
capacity of vac uum vessel (m3)  
<22 1.5 
>22 <54 4 
>54 <76.1  10 
>76.1  <108 20 
>108 <159 35 Test Code Sheet  2 2 1 3 ● 15  Draft Issue  No. 2 
        Date of Issue: December  2022  
Sheet  10 of 10 
 
Figure A1: Arrangement of apparatus for vacuum test  
 
Drawing is diagrammatic only  
Key. 
1 Vacuum pump  4 Full -way valve  
2 Vacuum gauge A  5 Vacuum gauge B  
3 Vacuum vessel  6 Length 5 DN to 10 DN 32 5
64
1  
 
Test Code Sheet 2213.20 Type AUK4  
    
Test Code Sheet  2 2 1 3 ● 20  Draft Issue : No. 1 
        Date of Issue: December  2022 
Sheet  1 of 10 
 
1. PURPOSE 
Type AUK 4 air gap arrangement verification as described in the Specification for the 
Prevention of Backflow . 
2. TYPE OF TEST(S)  
Dimensional  and internal overflow compatibility  
3. WATER REGULATIONS REQUIREMENTS FOR FITTINGS  
Schedule 2  
15 (1) …every water system shall contain an adequate device or devices for 
preventing backflow of fluid from any  appliance, fitting or process from occurring.  
4. BRITISH STANDARDS OR WATER SPECIFICATION, DEEMED TO 
SATISFY WATER REGULATIONS  
REQUIREM ENTS  
4.1 None 
5. GENERAL T OLERANCES AND MEASUREMENTS  
In the absence of specific tolerances or accuracies the following shall apply.  
1. Dimension : up to and including 75 mm ±5% ; over 75 mm ±2% . 
2. Flow rate and pressure: ± 5 % of the value specified.  
3. Temperature:  cold water ± 10 °C of the value specified.  
4. Linear measuring instruments shall have a minimum resolution of 0. 5 mm. 
5. Timing instruments shall have a minimum resolution of 0. 1 seconds . 
6. All the measuring instruments shall have an error limit of ±2 % of the measured 
value.  
6. TEST PROCEDURE  
6.1 Tests applicable to the following: - Test Code Sheet  2 2 1 3 ● 20  Draft Issue: No. 1 
        Date of Issue: December  2022  
Sheet  2 of 10 
 
TYPE AUK 4 AIR GAP DEVICE WITH INTERPOSED FLUSHING CISTERN  
Devices for the prevention of contamination by backflow.   This arrangement  may only 
be used with a flushing cistern and appropriate receiving vessel.  
 
 
(A) TYPE AUK 4 - AIR GAP DEVICE WITH INTERPOSED FLUSHING 
CISTERN 
TEST METHOD  
A1 Scope  
Procedure A specifies the characteristics of Type AUK 4 air gaps. Air gaps that comply 
with t he requirements of this procedure are devices for protection of wholesome water 
installations from contamination within a flushing cistern for example as part of a WC 
suite  or urinal . 
This is the  performance criteria for Type AUK 4 air gaps. Materials of construction must 
be fit for the purpose and application to ensure compliance with this procedure during 
normal working use.  
A2 Definitions  
Definitions as referenced in the Water Supply (Water Fittings) Regulations 1999 and 
Specification on the Prevention of Backflow . 
i. Type  AUK4 air gap with interposed flushing cistern  
Type AUK 4 air gap with interposed flushing cistern is a non- mechanical backf low 
prevention arrangement consisting of a flushing cistern feeding by gravity a receiving 
vessel (e.g. WC pan) . The interposed flushing cistern incorporates a Type AG or Type 
AC air gap and an overflow . The spill -over level of the receiving vessel (e.g. W C pan ) 
being located not less than 150 millimetres below the overflow pipe (or combined warning/overflow pipe), and not less than 15 millimetres below the internal spillover 
level with all devices (e.g. flushing valve and associated attachments)  completely 
removed  (see Figure 2) . 
ii. F lushing cistern  
Means a cistern provided with valve or device for controlling the discharge of the 
stored water into a water closet pan or urinal;  Test Code Sheet  2 2 1 3 ● 20  Draft Issue: No. 1 
        Date of Issue: December  2022  
Sheet  3 of 10 
 
iii. Flushing device  
Device fitted to a flushing cistern to provide controlled measured volume(s) of water to 
a receiving vessel  for flushing. 
NOTE  1: A flushing device can be a siphon, drop valve, flap valve or pressurised 
cistern etc. The flushing device includes the activator (i.e. handle, button, linkages, 
etc.) and  all seals, pistons, or other integral components . 
iv. Spillover level  
Means the level at which the fluid in a receptacle will first spill over the top edge of a 
receptacle if the inflow of water exceeds the outflow through any outlet and any 
overflow pipe.  
v. Graphic symbol  
 
A3 Designation  
The air gap is designated by : 
• its Type  
• the DN of the feed pipe to the assembly  
A4 Materials 
The manufacturer shall state the type of materials chosen in his technical and commercial documents.  
The surface condition of materials in contact with water shall be chosen to be the least 
inclined to scale.  
The materials used upstream, and including the atmospheric outlet opening ( e.g. for 
Type AC  air gap the air port inlet) , must comply with  BS 6920 or other national 
standard which provides an equivalent level of protection or performance. 
The choice of other material is discretionary but shall be suitable for the intended use of the appliance (temperature, corrosion, scale, etc).  AUK4Test Code Sheet  2 2 1 3 ● 20  Draft Issue : No. 1 
        Date of Issue: December  2022  
Sheet  4 of 10 
 
There are no special requirements concerning the materials used downstream of the 
atmospheric outlet opening provided they do not have any harmful effect on the 
upstream part . 
A5 Design  
i. General  
The protection assembly comprises of the following parts:  
a) A single w ater inlet device  
b) Flushing device  
c) An overflow/warning pipe  
d) Flushing cistern  
e) Receiving vessel  
ii. Water inlet device  
Every float -operated valve or other device which controls the inflow of water to a 
flushing cistern shall be securely and rigidly fixed to that cistern.  
Every fee d pipe supplying water to such a valve or other device shall be fixed in its 
position to prevent it from moving or buckling.  
Submerged supply pipes or inlet devices  within the flushing cistern shall not have a 
mechanical joint (see Note 2 ) at or below the critical water level (h). 
NOTE 2 : Mechanical joints are joints which when undone open a direct 
pathway between the wholesome water (incoming supply) and the water stored 
within the flushing cistern. These include joints that:  
a) are ‘adjustable’ or can be ‘dismantled’; or  
b) rely on elastomeric, or other material, to provide a water -tight seal; or  
c) where the coupling of two components being dependent upon mechanically applied forces, with or without the use of secondary seal.  
Joints not considered mechanical j oints include:  
a) Nuts or jointing mechanism on the diaphragm housing assembly.  
b) Joints where the joining surface are permanently fused together, for 
example by a chemical process or the application of heat.  Test Code Sheet  2 2 1 3 ● 20  Draft Issue: No. 1 
        Date of Issue: December  2022  
Sheet  5 of 10 
 
iii. Air gap  
The air gap shall conform to either a Type AC air gap (Test C ode Sheet 2213.15) or a 
Type AG air gap (Test C ode Sheet 2212.3). 
iv. Warning pipe and overflow arrangements  
a) The overflow shall be capable of draining off the maximum inlet flow.  
b) Shall not be less than 19mm internal diameter.  
c) Overflow arrangements must include an air break prior to a connection to drain. 
An air break to drain must conform to Test Code Sheet 2212.10 or  BS EN 
1717.  
NOTE 3: Clauses A5 iv b) and A5 iv c) do not apply to a WC suite, or urinal,  where the 
overflow discharges internal to the bowl providing the overflow is not less than 19 mm 
internal diameter at the point water enters the overflow to be discharged ; and the 
critical water level (h) has been verified by test.  
Figure 1 Type AUK 4 air gap with interposed flushing cistern  
   
 Type AUK4  Type AC  Type AG  
 arrangement  air gap  air gap  
Key for Figure 1  
1 service valve 
2 inlet device 
3 air gap (type AC or AG)  
4 dimension (h)  above the 
spillover level  
5 inlet device air gap reference 
point : 
a) Type AC air gap, lowest point 
of air inlet orifice  b) Type AG air gap, lowest point 
of discharge 
6 maximum water level  
7 critical water level (h)  
8 overflow invert  level 
9 ≥150 mm  
10 internal spillover level with 
flushing devices etc.  removed 
11 ≥15 mm  12 receiving vessel spillover level  
13 receiving vessel (e.g. WC pan)  
14 receiving vessel outlet  
15 discharge pipe from interposed flushing cistern 
16 flushing device  
17 overflow  
18 interposed flushing cistern 111 2 3 4
5
6
7
8
9
10
12
131617
1518
145a1 2
185b1 2
18Test Code Sheet  2 2 1 3 ● 20  Draft Issue : No. 1 
        Date of Issue: December  2022  
Sheet  6 of 10 
 
 A6 APPARATUS  
The following apparatus is required:  
a) Measuring equipment  with an accuracy of 0. 5 mm. 
A7 PROCEDURE  
The procedure shall be as follows:  
a) WC pan with associated flushing cistern and/or flushing device, or a close 
coupled/one- piece suite, all meeting the appropriate requirements of this 
specification, installed in accordance with the manufacturer's instructions on a 
firm, flat horizontal/vertical surface as appropriate.  
b) Ensure that the interposed flushing cistern complies with the requirements of 
Type AC  air gap ( Test Code Sheet 2213.15) or Type AG air gap  (Test Code 
Sheet 2212.3).  
c) With the flushing device completely removed use sufficient water to establish the 
residual fluid level within the flushing cistern.  
d) Allow sufficient time for the fluid level to stabilise. Measure the dimension between the spillover level of the receiving vessel (e.g. WC pan ) and the lowest 
internal residual fluid level of the interposed flushing cistern.  
e) Measure the dimension between t he spillover level of the receiving vessel (e.g. 
WC pan)  and the invert level of the overflow  pipe.  
  Test Code Sheet  2 2 1 3 ● 20  Draft Issue: No. 1 
        Date of Issue: December  2022  
Sheet  7 of 10 
 
 Figure 2 Flushing cistern showing the internal spillover level  
 
Key for Figure 2  
10 internal spillover level with 
flushing devices etc.  removed 
11 ≥15 mm  
12 receiving vessel spillover level  13 receiving vessel (e.g. WC pan)  
14 receiving vessel outlet  
15 discharge pipe from interposed 
flushing cistern 16 flushing device removed 
17 overflow removed 
18 interposed flushing cistern 
(B) TYPE AUK 4 - COMPONENT COMPATIBILITY (INTERNAL OVERFLOW)  
TEST METHOD  
B1 Scope  
Procedure B specifies additional verification requirements and applies to all WC Suites 
incorporating Type AUK4 air gaps unless they include one or more of the following:  
• An inlet valve achieving a Type AG air gap;  
• A diaphragm operated siphon; or  
• An overflow which discharges external to the WC suite (i.e. overflowing water 
does not return to the flush pipe or WC pan).  
When tested as described in B4 no fluids (discounting droplets) rise within the 
overflow pipe to a level less than or equal to 20 mm,  measured vertically down from 
the overflow invert level . 
B2 Pre-testing  
The following tests shall be successfully completed prior to  undertaking th e test. 
a) verification of warning and overflow provision (Test Code Sheet 5011.7 ); 
b) verification of f lushing volume (Test Code Sheet 3212.1); 
c) verification of the flush rate ( Test Code Sheet 1511.2); 
Test Code Sheet  2 2 1 3 ● 20  Draft Issue : No. 1 
        Date of Issue: December  2022  
Sheet  8 of 10 
 
 d) verification of an  air gap (e.g. T ype AC air gap -  Test Code Sheet 2213.15) ; 
e) verification of the Type AUK 4 backflow prevention arrangement  – Procedure A 
above.  
B3 Apparatus  
a) Receiving vessel  with associated flushing cistern ( e.g. close coupled, low level, 
concealed etc.), or one -piece WC suite, with a flushing device, 
warning/overflow and inlet valve meeting the appropri ate requirements of the 
Regulator’s WC Suite Performance Specification;  
b) Appropriate device(s) to block the outlet of the receiving vessel (e.g. WC pan) 
and any external warning provisions (e.g. warning pipe);  
c) Continuity probes with a latched indicator circ uit, or a no less effective method;  
d) Measuring instrument ; 
e) Water supply controlled by a stop valve  as appropriate.  
Figure 3 (informative) diagram showing continuity probe method  
 
B4 Procedure  
a) Assemble all components of the assembly (e.g. WC suite ) including fittings 
following the manufacturers' installation instructions, on a firm, flat horizontal/vertical surface as appropriate;  
b) Block  all outlet s of the receiving vessel (e.g. WC trap) and any external warning 
provision (e.g. warning pipe);  
c) Fill the receiving vessel with water to the spillover level of the receiving vessel ; 
Test Code Sheet  2 2 1 3 ● 20  Draft Issue : No. 1 
        Date of Issue: December  2022  
Sheet  9 of 10 
 
 d) Fill the flushing cistern to the invert level of the overflow. If the inlet valve is 
connected to a water supply, turn off the water  supply  unless essential for the 
normal operation of the flushing device (see Notes  4-6); 
e) Ensure the internal surface of the internal overflow pipe is sufficiently free of 
moisture which would otherwise cause inaccurate measurement of the rising 
water ; 
f) Rapidly operate the flushing mechanism and allow the flushing cistern to drain 
during the full flush operation (see Note 7); 
g) Observe and record results appropriate for the test method, e.g. visually 
observed the level the fluid reached; continuity probe metho d if the  fluid 
exceeds the 20 mm level  (see Notes  5); 
h) Repeat test 5 times . 
NOTE 4 : Where a water supply is essential for the normal operation of the flushing 
device maintain the supply at a hydraulic pressure of 1.5 ±0.1 bar or the minimum required to operate the device whichever is the greater.  
NOTE 5: To prevent the water within the flushing cistern accidentally spilling over the 
invert into the overflow a shield is permitted to be applied to the external surface of the overflow pipe.  
NOTE 6 : Where th ere are multiple water and overflow levels; or combinations of 
flushing device(s) and or overflow(s) the test shall be completed for each qualifying combination (see B 4). 
NOTE 7 : Operating the flushing mechanism (e.g. the time taken to operate the 
lever/button and fully activate the full flush) within approximately 1 second is considered ‘rapid’ and within approximately 3 seconds ‘slow’.  
B5 Expression of results  
Record compliance or any failure to comply, with the requirements.  
7. ACCEPTANCE  CRITERIA  
6.1 Test method (A)  
When tested as described in A7:  
a) The assembly must satisfy the appropriate requirements for Type AC  air gaps 
(Test Code Sheet 2213.15) or Type AG air gaps  (Test Code Sheet 2212.3); and 
b) With the flushing device completely removed,  the measurement between the 
spillover  level of the receiving vessel and the lowest internal residual fluid level  Test Code Sheet  2 2 1 3 ● 20  Draft Issue : No. 1 
        Date of Issue: December  2022  
Sheet  10 of 10 
 
 of the interposed flushing cistern  is equal to or greater than 15 mm. See Figure 
1; and  
c) The measurement between the spillover level of the receiving vessel and the 
invert level of the overflow  is equal to or greater than 150 mm.  
6.2 Test method (B)  
When tested as described in procedure B4 no fluids rise within the overflow pipe to a 
level less than or equal to 20 mm, measured vertically down from the invert level of the 
overflow .   
 
Test Code Sheet 2213.21 Joints below critical 
water level  
    
Test Code Sheet  2 2 1 3 ● 21  Draft Issue  No. 1 
        Date of Issue: December  2022  
Sheet  1 of 5 
 
1. PURPOSE 
Inlet valve: Joints below the water line verification  as described in WC Suite 
Performance Specifications . 
2. TYPE OF TEST(S)  
Joints below critical water level . 
3. REGULATION REQUIREMENTS FOR FITTINGS.  
Schedule 2 
25. (1) Subject to the following provisions of this paragraph-  
a. every water closet pan shall be supplied with water from a flushing 
cistern, pressure flushing cistern or pressure flushing valve, and shall be so made and installed that after normal use its contents can be cleared 
effectively by a single flush of water, or, where the installation is designed 
to receive flushes of different volumes, by the largest of those flushes;  
b. no pressure flushing valve shall be installed-  
i. in a house, or  
ii. in any building not being a house whe re a minimum flow rate of 1.2 
litres per second cannot be achieved at the appliance;  
c. where a pressure flushing valve is connected to a supply pipe or distributing pipe, the flushing arrangement shall incorporate a backflow prevention device consisting of a permanently vented pipe interrupter located not less than 300mm above the spillover level of the WC pan or  
urinal:  
d. no flushing device installed for use with a WC pan shall give a single 
flush exceeding 6 litres;  
e. no flushing device designed to give flushes of different volumes shall have a lesser flush exceeding two- thirds of the largest flush volume;  
f. every flushing cistern, other than a pressure flushing cistern, shall be clearly marked internally with an indelible line to show the intended volume of flush, together with an indication of that volume;  Test Code Sheet  2 2 1 3 ● 21  Draft Issue  No. 1 
        Date of Issue: December  2022  
Sheet  2 of 5 
 
g. a flushing cistern designed to give flushes of different volumes - 
i. shall have a readily discernible method of actuating the flush of 
different volumes; and  
ii. shall have instructions, clearly and per manently marked on the 
cistern or displayed nearby, for operating it to obtain the different volumes of flush;  
h. every flushing cistern, not being a pressure flushing cistern or a urinal cistern, shall be fitted with a warning pipe or with a no less effectiv e 
device;  
i. every urinal that is cleared by water after use shall be supplied with water from a flushing device which-  
i. in the case of a flushing cistern, is filled at a rate suitable for the installation;  
ii. in all cases, is designed or adapted to supply no mor e water than is 
necessary for effective flow over the internal surface of the urinal and for replacement of the fluid in the trap; and  
j. except in the case of a urinal which is flushed manually, or which is flushed automatically by electronic means after use, every pipe which 
supplies water to a flushing cistern or trough used for flushing a urinal shall be fitted with an isolating valve controlled by a time switch and a lockable isolating valve, or with some other equally effective automatic device for regul ating the periods during which the cistern may fill.  
(2) Every water closet, and every flushing device designed for use with a water closet, shall comply with a specification approved by the regulator for the purposes of this Schedule.  
(3) The requirements  of sub- paragraphs (1) and (2) do not apply where faeces 
or urine are disposed of through an appliance that does not solely use fluid to remove the contents.  
(4) The requirement  in sub -paragraph (1)(i) shall be deemed to be satisfied - 
a) in the case  of an aut omatically operated flushing cistern servicing urinals 
which is filled with water at a rate not exceeding-  
i. 10 litres per hour for a cistern serving a single urinal;  
ii. 7.5 litres per hour per urinal bowl or stall, or, as the case may be, for each 700 mm width  of urinal slab, for a cistern serving two or 
more urinals;  Test Code Sheet  2 2 1 3 ● 21  Draft Issue  No. 1 
        Date of Issue: December  2022  
Sheet  3 of 5 
 
b) in the case of a manually or automatically operated pressure flushing 
valve used for flushing urinals which delivers not more than 1.5 litres per 
bowl or position each time the device is operated.  
(5) Until 1st January 2001 paragraphs (1)(a) and (d) shall have effect as if they provided as follows - 
a) “every  water closet pan shall be supplied with water from a flushing cistern 
or trough of the valveless type which incorporates siphonic apparatus; ” 
b) “no flushing device installed for use with a WC pan shall give a single flush 
exceeding 7.5 litres; ”. 
(6) Notwithstanding sub- paragraph 1(d), a flushing cistern installed before 1st 
July 1999 may be replaced by a cistern which delivers a similar volume and 
which may be either single flush or dual flush; but a single flush cistern may 
not be so replaced by a double flush cistern.  
(7) In this paragraph-  
 “pressure flushing  cistern ” means a WC flushing device that utilises the 
pressure of water within the cistern supply pipe to compress air and increase 
the pressure of water available for flushing a WC pan;  
 “pressure flushing valve”  means a self -closing valve supplied with water 
directly from a supply pipe or a distributing pipe which when activated will 
discharge a pre -determined flush volume;  
 “trap” means a pipe fitting, or part of a sanitary appliance, that retains liquid 
to prevent the passage of foul air; and  
 “warning pipe”  means an overflow pipe whose outlet is located in a position 
where the discharge of water can be readily seen.  
4. BRITISH STANDARD OR WATER SPECIFICATION DEEMED TO 
SATISFY WATER REGULATIONS  REQUIREMENTS.  
4.1 None 
5. GENERAL T OLERANCES AND MEASUREMENTS  
In the absence of specific tolerances or accuracies the general tolerances and 
measurements set out in the WC Suite Performance Specifications shall apply . 
6. TEST PROCEDURE.  
6.1 Tests are applicable to the following fittings.  
Water inlet devices and connecting pipes within a WC flushing cistern . Test Code Sheet  2 2 1 3 ● 21  Draft Issue  No. 1 
        Date of Issue: December  2022  
Sheet  4 of 5 
 
(A) ALL WC CISTERNS SUPPLIED EITHER AS SUITES OR SEPARATLY, 
WHICH REQUIRE TO BE TESTED TO THE REGULATOR’S  
SPECIFICATION FOR WC’S.  
6.2 Apparatus  
a) cistern, complete with fitments including, inlet val ve flushing device, overflow, 
warning pipe (or no less effective arrangement) and flushpipe.  
b) water supply  
6.3 Procedure  
a) install cistern, complete with all fitments in accordance with the 
manufacturer's instructions;  
b) Determine the critical water level using the procedure set out in the Test Code Sheet appropriate for the backflow prevention arrangement (i.e. Type AC air gap - TCS 2213.15 or Type AG TCS 2212.3);  
c) At the critical water level inspect all mechanical joints.  
Mechanical joints are j oints w hich when undone open a direct pathway between the 
wholesome water (incoming supply) and the fluids stored within the flushing cistern.  
These include joints  that: 
a. are ‘adjustable’ or can be ‘dismantled’; or  
b. rely on elastomeric, or other material, to provide a water -tight seal; or  
c. where the coupling of two components being dependent upon mechanically 
applied forces, with or without the use of secondary seal.  
Joints not considered mechanical joints  include:  
a. Nuts or jointing mechanism on the diaphragm housing assembly.  
b. Joints where the joining surface are permanently fused together, for example by 
a chemical process or the application of heat.  
6.4 Expression of results  
Record the compliance or any failure to comply with the requirements.  
 
 Test Code Sheet  2 2 1 3 ● 21  Draft Issue  No. 1 
        Date of Issue: December  2022  
Sheet  5 of 5 
 
7. ACCEPTANCE CRITE RIA 
When tested as described in6 .3 no mechanical joints within a flushing cistern on 
submerged supply pipes or inlet devices shall be at or below the critical water level.    
 
Test Code Sheet 5011.7 Warning pipe and 
overflow provision  
    
Test Code Sheet  5 0 1 1 ● 7  Draft Issue : No. 2 
        Date of Issue: December  2022  
Sheet  1 of 5 
 
1. PURPOSE 
Flushing Cisterns: Warning and Overflow Pipe Provision verification as described in 
WC Suite Performance Specifications.  
2. TYPE OF TEST(S)  
Warning pipe and overflow provision.  
3. REGULATION REQUIREMENTS FOR FITTINGS.  
Schedule 2 
25. (1) Subject to the following provisions of this paragraph-  
a. every water closet pan shall be supplied with water from a flushing 
cistern, pressure flushing cistern or pressure flushing valve, and shall be so made and installed that after normal use its contents can be cleared effectively by a single flush of water, or, where the installation is designed to receive flushes of different volumes, by the largest of those flushes;  
b. no pressure flushing valve shall be installed-  
i. in a house, or  
ii. in any building not being a house where a minimum flow rate of 1.2 
litres per second cannot be achieved at the appliance;  
c. where a pressure flushing valve is connected to a supply pipe or distributing pipe, the flushing arrangement shall incorporate a backflow 
prevention device consisting of a permanently vented pipe interrupter 
located not less than 300mm above the spillover level of the WC pan or  
urinal:  
d. no flushing device installed for use with a WC pan shall give a single 
flush exceeding 6 litres;  
e. no flushing device designed to give flushes of different volumes shall 
have a lesser flush exceeding two- thirds of the largest flush volume;  
f. every flushing cis tern, other than a pressure flushing cistern, shall be 
clearly marked internally with an indelible line to show the intended 
volume of flush, together with an indication of that volume;  Test Code Sheet  5 0 1 1 ● 7  Draft Issue : No. 2 
        Date of Issue: December  2022  
Sheet  2 of 5 
 
g. a flushing cistern designed to give flushes of different volumes - 
i. shall have a readily discernible method of actuating the flush of 
different volumes; and  
ii. shall have instructions, clearly and permanently marked on the 
cistern or displayed nearby, for operating it to obtain the different 
volumes of flush;  
h. every flushing ciste rn, not being a pressure flushing cistern or a urinal 
cistern, shall be fitted with a warning pipe or with a no less effective device;  
i. every urinal that is cleared by water after use shall be supplied with water 
from a flushing device which-  
i. in the case of  a flushing cistern, is filled at a rate suitable for the 
installation;  
ii. in all cases, is designed or adapted to supply no more water than is 
necessary for effective flow over the internal surface of the urinal and for replacement of the fluid in the trap; and 
j. except in the case of a urinal which is flushed manually, or which is 
flushed automatically by electronic means after use, every pipe which 
supplies water to a flushing cistern or trough used for flushing a urinal 
shall be fitted with an isolating valv e controlled by a time switch and a 
lockable isolating valve, or with some other equally effective automatic 
device for regulating the periods during which the cistern may fill.  
(2) Every water closet, and every flushing device designed for use with a wate r 
closet, shall comply with a specification approved by the regulator for the purposes of this Schedule.  
(3) The requirements of sub- paragraphs (1) and (2) do not apply where faeces 
or urine are disposed of through an appliance that does not solely use fluid to remove the contents.  
(4) The requirement  in sub -paragraph (1)(i) shall be deemed to be satisfied - 
a) in the case  of an automatically operated flushing cistern servicing urinals 
which is filled with water at a rate not exceeding-  
i. 10 litres per hour for a cistern serving a single urinal;  
ii. 7.5 litres per hour per urinal bowl or stall, or, as the case may be, for each 700 mm width of urinal slab, for a cistern serving two or 
more urinals;  Test Code Sheet  5 0 1 1 ● 7  Draft Issue : No. 2 
        Date of Issue: December  2022  
Sheet  3 of 5 
 
b) in the case of a manually or automatically operated pressure flushing 
valve used for flushing urinals which delivers not more than 1.5 litres per 
bowl or position each time the device is operated.  
(5) Until 1st January 2001 paragraphs (1)(a) and (d) shall have effect as if they provided as follows - 
a) “every  water closet pan shall be supplied with water from a flushing cistern 
or trough of the valveless type which incorporates siphonic apparatus; ” 
b) “no flushing device installed for use with a WC pan shall give a single flush 
exceeding 7.5 litres; ”. 
(6) Notwithstanding sub- paragraph 1(d), a flushing cistern installed before 1st 
July 1999 may be replaced by a cistern which delivers a similar volume and 
which may be either single flush or dual flush; but a single flush cistern may 
not be so replaced by a double flush cistern.  
(7) In this paragraph-  
 “pressure flushing  cistern ” means a WC flushing device that utilises the 
pressure of water within the cistern supply pipe to compress air and increase 
the pressure of water available for flushing a WC pan;  
 “pressure flushing valve”  means a self -closing valve supplied with water 
directly from a supply pipe or a distributing pipe which when activated will 
discharge a pre -determined flush volume;  
 “trap” means a pipe fitting, or part of a sanitary appliance, that retains liquid 
to prevent the passage of foul air; and  
 “warning pipe”  means an overflow pipe whose outlet is located in a position 
where the discharge of water can be readily seen.  
4. BRITISH STANDARD OR WATER SPECIFICATION DEEMED TO 
SATISFY WATER REGULATIONS  REQUIREMENTS.  
4.1 None  
5. GENERAL T OLERANCES AND MEASUREMENTS  
In the absence of specific tolerances or accuracies the general tolerances and 
measurements set out in the WC S uite Performance Specifications shall apply . 
6. TEST PROCEDURE.  
6.1 Tests are applicable to the following fittings.  Test Code Sheet  5 0 1 1 ● 7  Draft Issue : No. 2 
        Date of Issue: December  2022  
Sheet  4 of 5 
 
ALL WC CISTERNS SUPPLIED EITHER AS SUITES OR SEPARATLY, which require 
to be tested to the regulator’s specification for  WC suites . 
(A) ALL WC CISTERNS SUPPLIED EITHER AS SUITES OR 
SEPARATLY, WHICH REQUIRE TO BE TESTED TO THE 
REGULATOR’S  SPECIFICATION FOR WC’S.  
6.2 Apparatus  
a) the cistern with warning pipe connection or a device deemed to be no less 
effective and internal overflow, if provided,  installed in accordance with the 
manufacturer’s instructions.  
b) measuring device.  
c) water supply controlled by a stop valve.  
6.3 Procedure  
1. Set the cistern level.  
2. Fill with water to the nominal static water level marked by the manu facturer.  
3. Measure the distance from the water level to the warning level, i.e. the invert 
of a side connection warning pipe connection or top of a bottom connection 
warning pipe connection. If appropriate, measure the distance from the 
warning level to the top of any internal overflow.  
Note: In some instances, such as with syphons, the levels may need to be 
determined by fil ling with water to the appropriate warning and overflow level.  
6.4 Expression of results  
Record the compliance or any failure to comply with the requirements.  
7. ACCEPTANCE CRITERIA  
Reference Figure 1 & 2 for dimensional requirements.  
When tested as described in 6 .3, every flushing cistern, not being a pressure flushing 
cistern, shall be arranged-  
a) in the case of a combined warning and overflow pipe (Figure 1) - 
i. with the discharge level between 20 mm and 51 mm inclusive, above the 
marked water level.  
or 
b) in the case of separate warning and overflow pipes (Figure 2) - Test Code Sheet  5 0 1 1 ● 7  Draft Issue : No. 2 
        Date of Issue: December  2022  
Sheet  5 of 5 
 
i. fitted with a warning pipe arranged with the discharge level  between 20 
mm and 41 mm inclusive above the marked water level; and  
ii. the top edge of any internal overflow between 30 mm and 51 mm 
inclusive and not less than 10 mm above the warning level.  
An alternative, no less effective device, may be used in place of a warning pipe.  
 
Figure 1 - Flushing cistern with combined warning and overflow provision  
 
Figure 2 - Flushing cistern with separate warning and overflow provisions  
To be withdrawn:   
 
Test Code Sheet 5011.5 Overflow –  
Measurement of dimension  
 WRc Evaluation & Testing Centre Ltd  
Test Code 
S
heet 
Number 5 0 1 1 5 
W
BS  TEST & ACCEPTANCE CRITERIA Issue No: 1 
PD. Date of issue: October 1998 
Sheet 1 of 2 
TEST CODE SHEET  
_______________________________________________________________________________________________________ 
1. TYPE OF TEST(S) 
Measurement of dimension.
2. BYELAW REQUIREMENT FOR FITTINGS
By
elaw 1
...... sp
ill-over level means the level at which the water in a cistern or vessel will first spill over if the inflow exceeds  
the outflow through any outlet and any overflow pipe.  
 ......warning pipe means an overflow pipe so fixed that its outlet, whether inside or outside the building, is in a  
conspicuous position where the discharge of water can be readily seen.  
Byelaw 39  
Every warning pipe shall be installed so as to discharge water immediately the water in the cistern reaches over flowing level. 
Byelaw 40  
No warning or overflow pipe shall comprise, include or have connected to it, any flexible hose. 
Byelaw 80  
Every flushing cistern or trough installed in any premises supplying water to a watercloset pan shall be fitted with a  
warning pipe and shall be indelibly marked on the inside with a line indicating the water level at which the float-operated 
 valve is to shut off when that cistern or trough operates to comply with the relevant provision of byelaws 75 to 77 and 79.  
3. BRITISH STANDARDS OR WATER SPECIFICATION, DEEMED TO SATISFY BYELAW REQUIREMENT
3.1 
At present no British Standard or Water Industry Specification exists.
4. TEST PROCEDURE 
Note   Unless otherwise stated the temperature of the test fluid shall be 20 ± 10°C.
4.1 Tests applicable to the following:-
VALVES
- flap for use with wc flushing cisterns
-drop for use with wc flushing cisterns
metal and plastic design.
____________________________________________________________________________________________________________ Specification to be withdrawn  Test Co
de 
Sheet 
Number 5 0 1 1 5 
I
s s u e  N o :  1
Date of issue: October 1998 
Sheet 2 of 2 
______________________________________________________________________________________________________ 
(A) DROP AND FLAP VALVE FOR USE WITH WC FLUSHING CISTERNS 
TEST METHOD 
Valves incorporating an ‘internal overflow to pan’ arrangement shall meet the following requirement.
(a)Measure the distance between the waterline in the cistern and the invert of the overflowing level of the external
warning pipe.
(b) Measure the distance between the waterline in the cistern and the invert of the ‘internal overflow’ of the valve.
5. ACCEPTANCE CRITERIA
(a)T
he distance between the invert of the overflowing level of the external warning pipe and the waterline, shall be not
less than 25mm or more than 32mm.
(b) The distance between the invert of the ‘internal overflow’ of the valve and the waterline shall be not less than the
25mm to 32mm as required in (a) with an additional 19mm. (ie. 44mm to 51mm above the waterline).
Specification to be withdrawn