Reference NBS

NAT'L INST. OF STAND & TECH

PUBLICATIONS AlllDb E ( 7 0

S

NBSIR 84-2860

Field Hydraulic Performance of

One- and Two-Story Residential

Plumbing Systems With

Reduced-Size Vents

Robert S. Wyly

Plumbing Consultant

and

Lawrence S. Galowin

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Building Equipment Division

Gaithersburg, MD 20899

May 1984

Issued October 1 984

Sponsored by

Tri Services,

Department of Defense,

QC

100

.U56

and

NO. 84-2860

1984

Department of Housing and Urban Development

NBSIR 84-2860

FIELD HYDRAULIC PERFORMANCE OF

ONE- AND TWO-STORY RESIDENTIAL

PLUMBING SYSTEMS WITH

REDUCED-SIZE VENTS

NATJONAl BUREAU! OF STANDARDS • LIBRARY , daoo

no. o

MM

Robert S. Wyly

Plumbing Consultant

and

Lawrence S. Galowin

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Building Equipment Division

Gaithersburg, MD 20899

May 1984

Issued October 1984

Sponsored by

Tri Services,

Department of Defense,

and

Department of Housing and Urban Development

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director

ABSTRACT

This report describes hydraulic tests of drain-waste-vent systems with

reduced-size vents installed in single-family housing units at Andrews Air

Force Base, Camp Springs, Maryland. The vent systems of six field units were

sized according to a procedure based on findings in prior laboratory investigations. The tests reported were conducted on three of the units before occupancy. Principal measurements made were trap-seal reduction and pneumatic

pressure excursions in selected vents, using laboratory test procedures adapted

to field conditions. Results of the preocupancy tests showed satisfactory

performance with the reduced-size vents. A procedure for the design of reducedsize vent systems is presented that provides methods for plumbing designers and

groups engaged in updating plumbing codes.

iii
ACKNOWLEDGMENTS

The program described in this report originated in response to a technical

implementation proposal prepared by Robert S. Wylyl for Paul Land, Directorate

of Civil Engineering, U.S. Air Force. The work was conducted under the administrative direction of Lawrence S. Galowin. Mary Jane (Orloski) Phillips^

directed activities relating to the design, and installation of the reducedsize vents, planned and conducted the preoccupancy tests, and prepared a draft

report presenting the results. The design, development and installation of

the automated data acquisition system and instrumentation package was directed

by Richard A. Grot, assisted by Lynn Schuman. Robert W. Beausoliel, Grover C.

Sherlin, Jr. and Robert S. Wyly contributed recommendations on instrumentation

design and measurement procedures. Members of the NBS Instrument Shop are acknowledged for their work in constructing some of the special sensors. Assistance in the evaluation of the as-built systems to determine conformance

of the drainage piping to the appropriate model plumbing code was provided by

George Williams, Chief Plumbing Inspector, Fairfax County, VA. , and by Dee

Rathbone, Plumbing Engineer. Capt. Kenneth Hanna (USAF) provided liaison

between the NBS project staff, the Andrews Air Force Base Civil Engineering

Office, the plumbing contractor, and the occupants of the test houses.

Robert S. Wyly and Lawrence S. Galowin expanded the initial draft report

prepared by Mary Jane (Orloski) Phillips and consolidated the design criteria

in the appendices from other NBS reports.

The work was first sponsored by the Directorate of Civil Engineering, U.S. Air

Force and later by the Building Research Committee of the Tri Services. A

significant portion of the project costs to obtain field data on water usage

and frequency of fixture operation was borne by the NBS Center for Building

Technology. The preparation of this report was sponsored by the Department of

Housing and Urban Development.

1 Currently Plumbing Consultant.

O^ Currently Mechanical Engineer, Bureau of Medicine and Surgery, Department of

the Navy.

iv
TABLE OF CONTENTS

Page

ABSTRACT iii

ACKNOWLEDGEMENTS iv

TABLE OF CONTENTS v LIST OF TABLES . * . ix

LIST OF FIGURES xi

DEFINITIONS xii

1. INTRODUCTION 1

1.1 OBJECTIVE AND SCOPE OF PROGRAM 1 1.2 BACKGROUND 1 1.3 PERFORMANCE CONCEPTS AND GENERAL APPROACH 2

2. SIZING OF VENTS 5

2.1 SIZING CRITERIA 5

2.1.1 Traditional Criteria 5

2.1.2 Criteria for RSV 5

2.2 APPLICATION OF RSV CRITERIA TO THREE DWV DESIGNS 5

3. INSTALLATION AND TESTING OF RSV SYSTEMS IN THE FIELD 17

3.1 ORGANIZATION AND SEQUENCE OF PROJECT ACTIVITIES 17

3.2 INSTALLATION OF INSTRUMENTATION AND REDUCED-SIZE VENTS 17

3.3 EVALUATION METHODOLOGY 18

3.3.1 Instrumentation 18

3.3.2 Test Procedures: Preoccupancy Tests 19

3.4 DATA SUMMARY AND DISCUSSION 21

3.4.1 Discharge Characteristics of Fixtures 21

3.4.2 Trap-Seal Reduction and Vent Pressure with Vent

Terminal Open 21

3.4.3 Trap-Seal Reduction and Vent Pressure with Vent

Terminal Closed 23

4. CONCLUSIONS 37

4.1 ADEQUACY OF PERFORMANCE OF THE RSV SYSTEM AT ANDREWS AIR FORCE

BASE AND ADEQUACY OF THE RSV CRITERIA 37

4.2 COST CONSIDERATIONS 37

4.3 RESIDUAL ISSUES AND CODE ACCEPTANCE 37

4.3.1 Residual Issues 37

4.3.2 Formulation of Code Changes and Generally Accepted

Design Procedures 38

5. REFERENCES 39

v
TABLE OF CONTENTS (continued)

Page

APPENDIX A. PREOCCUPANCY TESTS: DETAILED INFORMATION A-l

A.l DATA WITH VENT TERMINAL OPEN A-l

A. 2 DATA WITH VENT TERMINAL CLOSED A-2

APPENDIX B. POST-OCCUPANCY STUDY B-l

B. l APPROACH AND OBJECTIVE B-l

B. 2 RESULTS B-2

APPENDIX C. RECOMMENDED CRITERIA AND GUIDELINES FOR THE DESIGN AND

INSTALLATION OF REDUCED-SIZE VENTS FOR ONE- AND TWOSTORY HOUSING UNITS C-l

C. l INTRODUCTION C-l

C.2 GENERAL LIMITATIONS C~3

C. 3 PRELIMINARY DATA C-4

C.4 SIZING PROCEDURE C-5

C.4.1 Activity Sequence and Sizing Criteria C-5

C.4.

2

Illustrative Examples C-6

C.5 INSTALLATION GUIDELINES AND DATA FOR BUILDING OWNER C-7

C.6 APPROVAL OF RSV DESIGN C-9

C.7 CHRONOLOGICAL BIBLIOGRAPHY ON RSV C-9

vi
LIST OF TABLES

Page

Table 1. Organization and Sequence of Activities Relating to

Preoccupancy Hydraulic Tests . . 24

Table 2. Characteristics of Instruments and Purposes for

Which Used 25

Table 3. Symbols for Fixtures 26

Table 4. Water Level in Waste Fixtures for Discharge Rate

Measurements 27

Table 5. Guide for Selecting Test Loads for Residential Plumbing

Systems 28

Table 6. Plan for Testing Sequence and Certain Test Conditions in

Preoccupancy Hydraulic Tests 29

Table 7. Waste Fixture Discharge Characteristics Determined from

Field Calibrations of Fixtures In Place 30

Table 8. Water Closet Water Consumption Measured in D/a Unit 31

Table 9. Summary of Findings on Trap-Seal Reductions D, E, and F

Houses with Vent Terminals Open 32

Table 10. Summary of Findings on Vent Pressures in D, E, and F

Houses with Vent Terminals Open 33

Table A. 1.1 Trap-Seal Reduction with Vent Terminal Open A-4

Table A. 2.1 Summary of Findings on Trap-Seal Reductions in D and F

Houses with Vent Terminal Closed A-7

Table A. 2. 2 Trap-Seal Reduction with Vent Terminal Closed A-8

Table A. 2. 3 Effect on Idle Trap-Seal Reduction of Repeated Loading

without Refilling Traps between Runs, with Vent Terminal

Closed A- 10

Table A. 2. 4 Vent Pressure Data for the D/a Unit with Vent Terminal

Closed, W1 + W2 + T2 Discharged A- 1

1

Table B.2.1 Water Consumption in Occupied Test Unit D/a and Distribution

by Fixture and Outlet (data sample covering a 5 day

period) b-4

vii
LIST OF TABLES (continued)

Page

Table B.2.2 Water Consumption in Occupied Test Unit F/a and Distribution

by Fixture and Outlet (data sample covering a 5 day

period) B-5

Table C.4.1 Drainage Fixture Unit Load Ratings for Various Plumbing

Fixtures . C-l 1

Table C.4.2 Minimum Sizes for Individual and Common Fixture Vents and

for Stack Vents C-12

Table C.4.3 Minimum Sizes for Branch Vents C-13

Table C.4.4 Combinations of Three Fixture Vent Sizes Requiring a Branch Vent Two Pipe Sizes Larger than Largest Fixture

Vent Served by Branch Vent C-14

Table C.4.5 Internal Cross Sectional Areas of Various Nominal Sizes

of Pipe C-15

Table C.4.6 Minimum Sizes and Maximum Lengths for Vent Stacks C-16

Table C.4.7 Classification and Sizing of Dry Vents (Figure C.4.2,

Example 1) C— 17

Table C.4.8 Classification and Sizing of Dry Vents (Figure C.4.4,

Example 2) C-18

Table C.4.9 Sizing of Vent Headers (Figure C.4.5, Example 2) C-19

viii
LIST OF FIGURES

Page

Figure 1. Aerial view of test houses 4

Figure 2. Floor plan for D-house (as designed)

Figure 3. Floor plan for E-house (as designed) 8

Figure 4. Floor plan for F-house (as designed) 9

Figure 5. Original design, D-house soil, waste, and vent piping,

showing vent size reductions obtainable from RSV

criteria 10

Figure 6. Original design. E-house soil, waste, and vent piping,

showing vent size reductions obtainable from RSV

criteria 11

Figure 7. Original design, F-house soil, waste, and vent piping,

showing vent size reductions obtainable from RSV

criteria 12

Figure 8. Modified original design, F-house soil, waste, and vent

piping, showing manifolding of vent terminals and vent

size reductions obtainable from RSV criteria 13

Figure 9. As-built design, D-house soil, waste, and vent piping,

showing vent sizes obtained from RSV criteria 14

Figure 10. As-built design. E-house soil, waste, and vent piping,

showing vent sizes obtained from RSV criteria 15

Figure 11. As-built design, F-house soil, waste, and vent piping,

showing vent sizes obtained from RSV criteria 16

Figure 12. Instrumentation and data acquisition system 34

Figure 13. Method for measurement of cumulative time outside

preset pressure range 35

Figure 14. Definition of trap-seal reductions for testing purposes ... 36

Figure A. 2.1 Pattern of trap failures with repetitive, heavy loading

and closed vent terminal A- 12

Figure B.1.1 Schematic of automatic monitoring instrumentation for

post-occupancy tests B-6

Figure B.1.2 Schematic of post-occupancy field data acquisition system . B-7

ix
LIST OF FIGURES (continued)

Page

Figure B.2.1 Distribution of cold water flow rates in master bath

shower. D/a unit (data sample covering a 5 day period) .... B-8

Figure B.2.2 Distribution of hot water flow rates in master bath

shower, D/a unit (data dample covering a 5 day period) .... B-9

Figure B.2.3 Distribution of combined hot and cold water flow rates

in master bath shower. D/a unit (data sample covering a

5 day period) B-10

Figure B.2.4 Distribution of combined hot and cold water flow rates

in common bath shower head. D/a unit (data samples covering

a 5 day period) B-ll

Figure B.2.5 Distribution of cold water flow rates in master bath

shower, F/a unit (data sample covering a 5 day period) .... B-12

Figure B.2.6 Distribution of hot water flow rates in master bath

shower, F/a unit (data sample covering a 5 day period) .... B-13

Figure B.2.7 Distribution of combined hot and cold water flow rates in

master bath shower, F/a unit (data sample covering a 5 day

period) B-14

Figure C.4.1 Soil-waste-vent piping for 2-story single family

townhouse, showing a standard DWV design conforming to

the applicable plumbing code (compare with figure C.4.2

for RSV ) 020

Figure C.4.2 Soil-waste-vent piping for 2-story single family

townhouse, showing reduced sizes of dry vents obtainable

from RSV design criteria (compare with figure C.4.1 for

standard venting) 021

Figure C.4.3 Soil-waste-vent piping for 1-story single family

residence, showing a standard DWV design conforming to

the applicable plumbing code (compare with figure C.4.4

for RSV) 022

Figure C.4.4 Soil-waste-vent piping for 1-story single family

residence, showing reduced sizes of dry vents obtainable

from RSV design criteria (compare with figure C.4.3 for

standard venting) 023

x
LIST OF FIGURES (continued)

Page

Figure C.4.5 Soil-waste-vent piping for 1-story single family

residence, showing the use of a vent header to reduce the

number of roof penetrations (compare with figures C.4.3

and C.4.4 showing five penetrations) 024

xi
DEFINITIONS

In this report, a number of terms are used that require specialized definition

beyond the dictionary meaning of the words. Some terms used are adequately

defined in plumbing codes, but others are used in such a sense as to require

modified definition for the purposes of this report. Therefore, the following

definitions are provided as an aid to understanding.

Blowback - the ejection of suds, air, or other gases through the trap-seal

to the room side of a trap as a result of excessive positive pressure on

the drain side of the trap.

Branch - any part of the piping system other than a main, riser, or stack.

Branch vent - a vent pipe to which two or more fixture vents are connected

and which terminates by connection to a vent stack or a stack vent.

Building drain - that part of the lowest piping of a drainage system which

receives the discharge from soil, waste, and other drainage pipes inside

the walls of the building and conveys it to the building sewer.

Common vent - a fixture vent connecting at the junction of two fixture

drains and serving as a vent for both fixtures.

Cumulative dH - trap-seal reduction of an idle trap after a series of

fixture discharges without refilling the idle trap between such discharges.

dH - the amount of decrease in trap-seal depth from full-seal depth of an

idle trap following the discharge of other fixture(s) into the system.

Dip of trap - the highest point on the internal vertical cross section of

the trap at the lowest portion of the bend (inverted siphon).

dP - peak vent pressure (positive or negative) occurring during the

discharge of fixtures into the system.

Dry vent - any vent that does not carry water or waterborne wastes.

Fixture vent - a vent that provides the primary ventilation for one or two traps located in the proximity of the base of the vent.

Flood-level rim - the top edge of a receptacle or fixture bowl from which

water can overflow in the absence of or malfunction of an overflow device

at a lower elevation.

Frost closure - the partial or complete closure of a roof vent in cold

weather by the formation of a layer of frost on the inner surface of the

vent.

xii
Individual vent - a fixture vent installed to vent a single fixture and so connected with the vent system or with the open air that free movement of

air is possible at all times.

Induced siphonage - the process whereby a reduction in the surface level

of the trap-seal of an idle fixture is caused by the discharge of other

fixtures on the system, such discharge resulting in transient local pressure fluctuations that siphon, or otherwise remove, water from the idle

trap.

Reduced size venting (RSV) - a specially designed vent system (or the

procedure for such design) that contains dry vents smaller in size than

allowed by the applicable plumbing code for standard venting.

Soil stack - a stack intended to convey sewage containing fecal matter.

Stack - general term for the vertical main of the soil, waste, or vent

piping system.

Stack vent - a stack vent is the extension of a soil or waste stack above

the highest connection of a horizontal drain to the stack.

Trap - a fitting or device placed below a fixture outlet and constructed

so as to provide a water seal for protection against the emission of sewer

gases, without significantly retarding the flow of water through it.

Trap-seal - the vertical distance between the trap weir and the dip of the

trap.

Trap-seal reduction - same as dH.

Trap-seal retention - the amount of trap-seal retained following the

discharge of fixture(s) into the system.

Trap weir (crown weir) - the lowest point in the vertical cross section of

the horizontal waterway at the exit of the trap.

Vent - a pipe installed to provide a flow of air to or from a drainage

system or element thereof so as to provide protection of trap-seals from

siphonage and back pressure.

Vent header - a generally horizontal vent that joins together two or more stack vents and/or vent stacks, and terminates outside the building in the

atmosphere.

Vent stack - a vertical vent pipe extending through two or more stories,

installed to provide circulation of air between elements of the DWV

system. Usually, the vent stack is the vertical main of the vent system,

to which branch vents are connected.

xiii
Vent terminal - that portion of the vent piping extended outside the

building and open to the atmosphere.

Waste - liquid waste not including fecal matter.

Waste stack - a stack that conveys only waste.

xiv
1. INTRODUCTION

1.1 OBJECTIVE AND SCOPE OF PROGRAM

The principal objective of the research program described herein was to

evaluate field performance of reduced-size vents (RSV). Laboratory-based

vent-sizing criteria were applied to the modification of selected standard

drain-waste-vent (DWV) designs and measurements made to determine the field

hydraulic and pneumatic performance of the test units. In addition, the broad

overall scope of the program undertaken called for the acquisition of postoccupancy data on the magnitude and time distribution of hot and cold water by

fixture and of energy consumption by the water heater. Samples of the type of

data obtained in the post-occupancy study are presented in appendix B.

Laboratory-based criteria [1] were applied to resize the dry vents of two

living units each of three different standard DWV plans (a total of six units).

Sensors, transmission wiring, and a data acquisition system were installed for

the primary purpose of automatically monitoring, subsequent to occupancy:

(1) the hydraulic and pneumatic performance of the DWV system, (2) distribution

of fixture operations, (3) water consumption, and (4) energy used by the water

heaters

.

Preoccupancy field tests were made in three of the six units, in which trapseal reductions for idle traps and pneumatic pressure changes in vents were

measured when selected plumbing fixtures were discharged manually. Figure 1 is an aerial view of the test houses.

This report includes recommended design procedures, installation guidelines

and preoccupancy field test performance data for RSV systems.

1 . 2 BACKGROUND

Before the present study was initiated several reports describing laboratory

investigations of reduced-size venting had been issued [1, 2, 3, 4], and one field study had been reported [5]. Reduced-size venting was used in one single

family, one-story DWV design used in HUD's Operation Breakthrough Program [6]

apparently with satisfactory results. Those investigations showed the adequacy

of hydraulic and pneumatic performance of selected one- and two-story DWV systems with reduced-size vents under the conditions described. The principal

explanations offered for the satisfactory performance of those systems not

conforming to traditional vent sizing requirements were:

(a) Traditional sizing of vent stacks and stack vents is based on maximum air flow rates associated with conditions in a tall

building [7], where both the waste loading rates and the

accompanying air flow rates might be expected to be much

greater than occur in a one- or two-story building. Laboratory

data confirmed this, showing relatively low air demands in oneand two-story systems.

1
(b) Scientific criteria for the traditional sizing of individual and common fixture vents and for branch vents could not be identified;

analysis of installation practices and laboratory measurements indicated such vents, at least in one- and two-story systems are capable

of carrying much greater air flow rates that normally occur in service

when sized by plumbing code requirements.

(c) Traditional vent sizing was developed with an awareness of the

tendency of ferrous pipes to acquire, under some conditions,

surface corrosion deposits which could, over a period of time,

reduce the effective diameter of the pipe. But if modern piping

materials not subject to corrosion are used, this effect should

be negligible.

As a result of these findings suggesting potential for the demonstration of

of RSV as a viable type of venting, the U.S. Air Force and the Tri Services,

together with NBS , funded the field study described in this report. The

demonstration was intended to provide a basis for possible later general

application of RSV, with economic benefits, in the Tri Services family housing

construction programs. The highly instrumented homes were to provide field

data on water use and distribution of fixture operations needed for updating

the widely used Hunter method for sizing water supply piping. It was also

intended to provide a practical, generalized sizing procedure for use by

plumbing code organizations that may consider the inclusion of RSV criteria in

their codes.

Economic analyses of the impact of reduced-size venting [8] concluded that

under some conditions and methods of cost estimating, significant savings can

be anticipated from the installation of RSV. In these analyses, potential

savings in single family, one- and two-story residential installations ranged

from $24 to $151 per dwelling unit (1975 dollars). Cost reductions from RSV

are affected primarily by: (1) the specifics of the DWV system design including

pipe sizes, configuration, complexity, fixture locations, etc., (2) types and

availability of necessary piping materials, and (3) the nature of cost estimating procedures used and other business practices of the plumbing contractor.

These are essentially the principal factors that generally affect the cost of

plumbing. The studies showed that, while the unit savings from the lower

materials costs of smaller pipes and fittings may be relatively small, installation labor, overhead, and profit generally amplify this margin so that, for

example, a one dollar saving on the material cost of a length of pipe may

result in much more than a one dollar saving in the completed installation.

1.3 PERFORMANCE CONCEPTS AND GENERAL APPROACH

Performance concepts for plumbing in general, and sanitary DWV systems in

particular, have been treated at length in previous studies [9, 10, 11, 12] so the criteria and requirements will not be discussed here in detail. Let it

suffice to state that the performance criteria of particular interest in this

study were: (a) trap-seal retention in idle traps subjected to suction, and

(b) absence of emissions of water or suds through idle trap-seals subjected to

back pressure. Attention was also given to the principal phenomenon which

2
might produce the results measured by criteria (a) and (b): the fluctuating

suction or back pressure within the vent system pipe network itself.

In the preoccupancy tests, the general approach was to impose test loads

considered somewhat more severe than would be expected in normal service, and

to measure trap-seal reduction (the complement of trap-seal retention) and

pressure fluctuations in the vents. At the same time, test personnel listened

for noises indicating air flow through idle trap-seals which could indicate

excessive levels of back pressure or suction.

3
Figure 1 . Aerial view of test houses

4
2. SIZING OF VENTS

2.1 SIZING CRITERIA

2.1.1 Traditional Criteria

The traditional code requirements for sizing of stack vents and vent stacks

(main vents) are based on data from laboratory studies with multistory test

systems, applied conservatively [7, 13, 14]. The traditional criteria for

sizing individual, common and branch vents are more or less "rule-of-thumb,"

based on experience with ferrous vent piping materials (commonly used when these

rules were being formulated), which, under some conditions, can be subject to

gradual diameter reduction and increased surface roughness as a result of

corrosion. Also, it is recognized that intermittent discharge of a fixture

may, under some conditions, deposit a layer of particulate matter inside the

lower portion of a vent, further contributing to gradual closing of the vent over a period of time, regardless of the piping material used.

A review of this information indicated that in many systems dry vents sized

by traditional criteria are considerably larger than would be required to

accomodate the air flow with an acceptable pressure drop. The review suggested

that dry vent size reduction would be appropriate in low-rise systems, particular one- and two-story residences, and that such reduced-size venting should

be constructed of corrosion-resistant piping.

2.1.2 Criteria for RSV

The essential features of the RSV criteria applied in this study were presented

in an earlier publication [1]. The criteria used were technically similar to

those presently recommended in appendix C using an updated format.

In applying the criteria, the principal parameters to be considered are:

(1) "free-fall" distance for water discharge, (2) fixture unit load values(s)

of fixture(s) served by a particular vent, and (3) type or function of vent,

e.g., individual vent, branch vent, vent stack, etc. In addition, certain

limitations are critical, e.g., no size reductions are permitted wherever

wastewater might reasonably be expected to rise into the vent due to fouling

or blockage of a drain, and no reductions of wet vent or drainage piping sizes

are permitted below code minimums. See appendix C for further details.

2.2 APPLICATION OF RSV CRITERIA TO THREE DWV DESIGNS

The first step in sizing the vents for the study was to apply the RSV criteria

to the DWV schematics furnished by the sponsor prior to the beginning of con- struction. Figures 2 through 4 are floor plans showing the plumbing layouts

taken from the original design drawings. Figures 5 through 8 are soil, waste,

and vent piping riser diagrams showing vent sizes as originally specified by

the Air Force and as initially recommended by NBS on the basis of the RSV criteria [1]. Appendix C presents the criteria and a recommended procedure for

applying them.

5
The second step was to make revisions to the initially recommended RSV designs

to provide consistency with modifications to the installations due to onsite

contractor practices or other alterations dictated by field conditions differing

from the assumptions made in producing the initial schematics (see 3.1). The

"as-built" schematics are shown in figures 9 through 11.

6
WH

U ]f It u

Figure 2. Floor plan for D-house (as designed)

7

SECOND

FLOOR
IThm

o cc sZ

n co

Figure 3. Floor plan for E-house (as designed)

8

cw

SERVICE—

4

6

co

SECOND

FLOOR
WH 4

o V

o \

Figure 4. Floor plan for F-house (as designed)

9

1'CW

SERVICE
^-3'V.T.R.

Figure 5. Original design, D-house soil, waste, and vent piping, showing

vent size reductions obtainable from RSV criteria

10
Figure 6. Original design, E-house soil, waste, and vent piping, showing

vent size reductions obtainable from RSV criteria

11

3/4 )

BY

RSV

CRITERIA
3

VTR

<

GC

UJH

GC

Hi ^

O CO

O GC > >-

CO CQ

Figure 7. Original design, F—house soil, waste, and vent piping, showing

vent size reductions obtainable from RSV criteria

12
3

VTR

LUO

o

o

>

CD

I

Figure 8. Modified original design, F-house soil, waste, and vent piping,

showing manifolding of vent terminals and vent size reductions

obtainable from RSV criteria

13

3/4 )

BY

RSV

CRITERIA
Figure 9. As—built design, D~house soil, waste, and vent piping, showing vent

sizes obtained from RSV criteria

14
Figure 10. As-built design, E-house soil, waste, and vent piping, showing

vent sizes obtained from RSV criteria

15
Figure 11. As-built design, F-house soil, waste, and vent piping, showing vent

sizes obtained from RSV criteria

16
3. INSTALLATION AND TESTING OF RSV SYSTEMS IN THE FIELD

3.1 ORGANIZATION AND SEQUENCE OF PROJECT ACTIVITIES

At the outset it was necessary to consider the nature and sequence of project

activities in relation to the construction and occupancy schedules. Some

activities would have to be planned and/or completed before groundbreaking,

others during construction, and still others after completion of construction

but before occupancy of the test housing units. Table 1 shows the guide used

as an aid to the management and monitoring of these activities.

3.2 INSTALLATION OF INSTRUMENTATION AND REDUCED SIZE VENTS

Figure 1 shows the locations of the test units in a family housing development

at Andrews Air Force Base. During the early construction phase, underground

cable was laid connecting each test unit with the DAS central control unit

placed in a closet in the D/a module. In this terminology, e.g.. D/a, the

capital letter refers to the house type and the lower case letter refers to a particular module as designated in the architectural drawings (see figure 1).

Within each of the test dwelling units, wires were run within the walls between

the measurement points (primary sensors) and a centrally located closet selected

for housing the "satellite” DAS equipment cabinet. The DAS central unit

(recorder and printer), placed in the equipment closet of the D/a module, is

shown in figure 12.

Pressure taps were provided at selected points in the venting systems during

the installation of the DWV systems, and 3/8 in. O.D. diameter copper tubing

was run within the walls and floor-ceiling cavities to the equipment closet in

each test module. These tubes were continuously graded downward from the

highest point to assure moisture drainage. Each equipment cabinet contained,

among other things, three magnetically coupled differential pressure gages

connected to the tubing from the pressure taps.

Flow switches were installed in the individual hot and cold water supply lines

of lavatories, tubs and/or showers, kitchen sink, clothes washer, and in the

cold water supply to the water closets. Water meters were Installed in the

water service pipe and in the cold water branch to the hot water heater of each

instrumented housing unit.

The monitoring traps designed for automatically detecting trap-seal reductions

were installed for the bath tubs, clothes washers, and shower stalls in the

test units at appropriate times before drywall installation. Monitoring traps

for the lavoratories and kitchen sinks were installed after completion of the

drywall, and access panels to the clothes washer traps and flow switches were

also provided after completion of the drywall installation.

Connections were made to telephone transmission lines from the data acquisition

system on the housing site. The telephone lines could be used to carry data

directly to the NBS site in Gaithersburg, an air distance of approximatly

47 km (29 miles).

17
At the appropriate time during the installation of the rough piping, the

reduced-size vents were installed. Ideally, that would have been done simply

in accordance with the original design schematics as modified for RSV (see

figures 5 through 8). However, some modifications in the planned DWV configurations and sizes were necessitated because of building site conditions, and

because of field changes in the drainage piping systems introduced by the

plumbing contractor, (not an unusual situation). Before preoccupancy testing

was initiated, it was established that the as-built drainage (wet) systems

complied with the appropriate model plumbing code. In making the necessary

design revisions for the reduced-size vents of the as-installed, field test

systems, the sizing criteria were the same as previously applied for the first

modifications to the original design drawings. The "as-built" designs are shown in figures 9 through 11.

3.3 EVALUATION METHODOLOGY

3.3.1 Instrumentation

The project plan called for three types of data: (1) DWV system performance,

(2) water usage (distribution of fixture operations and volume of water used,

by time and fixture), and (3) energy usage (for each water heater). The

instrumentation developed for these measurements is described briefly in

table 2 and figures 12 and 13. See also appendix B.

The automated instrumentation designed for collection of post-occupancy DWV

system data, as well as other temporary installed instrumentation, was utilized during the preoccupancy tests. This provided for an opportunity for verification of the operational readiness of the automated system. Comparisons of

the trap-seal levels directly measured from piezometers or portable depthdetector probes were made with those measured by means of the data acquisition

system receiving the electrical signals from instrumented traps. Three

magnetically-coupled differential pressure gauges in each of three test modules were utilized during the preoccupancy tests to observe visually the peak vent

pressure excursions in selected tests for comparison with the corresponding

values recorded in the automated operation mode. The gauges were equipped to

automatically measure cumulative elapsed time over which vent pressure fluctuations fell outside a preselected pressure range; e.g. , + 25 mm WG (see

figure 13).

Water seal depth changes in some of the bathtub or shower traps were measured

in the preoccupancy tests by means of the portable depth-detector probe (figure

12); the traps were also instrumented for post-occupancy automatic data acquisition. Floor drain traps, however, were not instrumented for post-occupancy

automatic data collection because only relatively mild changes in water level

in the traps were expected during normal loading. This was confirmed in the

preoccupancy tests using the portable probe.

The flow switches on the hot and cold water supply lines to the fixtures

together with the two water meters (one in the house service pipe and the other

in the supply pipe to the water heater) provided a means of monitoring the time

distribution of water usage by fixture and the cumulative consumption of water.

18
It was planned that in the post-occupancy tests the data from the flow switches

and the traps would be processed to identify which fixture(s) were operated to

produce a water flow registered by the water meter(s), and to provide data on

the time distribution of the fixture operations.

In the preoccupancy tests, piezometers were utilized to read the water levels

in some of the instrumented traps. Peak vent pressures were observed visually

on the magnetically-coupled gauges for selected tests (see figure 13) while the

data acquisition system was automatically recording the cumulative time outside

the range + 0.25 kPa. Locations of pressure measurement taps are shown

schematically in figures 9 through 11.

3.3.2 Test Procedures: Preoccupancy Tests

The test plan covered four areas: organization of project activities; the

discharge characteristics of the fixtures; a selection of test conditions

(including specific test loads); and definitive test procedures.

Each of the fixtures in each of the houses was given an abbreviated

identification code (symbol) that would apply in all the houses. (See table

3).

Water depths for the waste fixtures (fixtures other than water closets) were

established, a selection of loading patterns was made, certain conditions of

test were selected, and the scope of measurements decided. Tables 4 through 6

and the following discussion describe these areas in greater detail.

The selection of hydraulic test loads for DWV system evaluation has not been

standardized. But preliminary analysis of the piping schematics showed that

specific hydraulic loads should be imposed to test the adequacy of particular

types of vents, and of the vent system as a whole. For example, appropriate

individual fixture discharges would test the fixture vents; simultaneous

discharge of two or more fixtures served by a particular branch vent would test

the branch vent; and generally three or more fixtures discharged simultaneously

would test the main vents and overall venting system. Some tests would be

necessary to evaluate the effect of detergents as used in the clothes washer

and the kitchen sink.

A review was made of several earlier reports on DWV testing. The load selection

guide, shown as table 5, for selecting test loads in the RSV preoccupancy field

study was based on [15] for single-branch interval portions of plumbing systems

and on other general requirements for hydraulic loading. The loads actually used were considered equal, or greater, in effect than those indicated by table 5.

The effects of the loads used are believed to have been at least as severe as might have been expected from service loadings imposed by building occupants.

Table 5 indicates the number of fixtures to be discharged. Judgment is required

to select which fixtures should be discharged when several are served by the

system or component being tested. Experience in performance evaluation of DWV

systems has shown that, generally, it is wise to choose two or three different

19
combinations so as to produce effects more or less representative of service

conditions.

In any bathroom group of three fixtures, it is reasonable to discharge two

fixtures and observe the effect on the third or idle fixture. In any back-toback bathroom arrangement, it is logical to test each group separately (as

immediately above), and also to discharge two fixtures in one bathroom and

observe the effect on the fixtures in the opposite bathroom or to discharge two

in one room and one in the other, observing any effects in either room. A

loading comprising two fixtures in each room would represent a very unusual

concentration of simultaneous operation and is precluded by table 5.

When the fixtures are distributed on two or three different levels, table 5 may

be used to aid in selecting test loads, using an approach similar to that given

above for back-to-back bathrooms on the same level. If some but not all of the

discharging fixtures are on the lowest level, measurable back pressure may be

produced at this elevation.

A "test" was defined to consist of four successive runs under conditions as identical as possible. Detergent, used in some of the tests, was introduced

on the first and third runs of a test (clean water used on runs two and four).

Four successive runs with detergent additives were not considered a realistic

test cycle. Readily available testing materials were used: 1-1/4 c. TIDE

laundry detergent in the clothes washer according to the manufacturer's directions; for the kitchen sink, 1/4 c. PAIMOLIVE detergent (sink bowls filled to

15 cm level as established in the fixture calibration determination). (The

designation c. is used for "cup" and products were selected due to availability.)

After a run was initiated, the peak readings on one or two selected pressure

gauges were observed visually. This information was correlated, where applicable,

with the elapsed time in seconds outside the range of + 0.25 kPa clocked by the

DAS (see figure 13).

Trap-seal elevations were read manually on the piezometers after each run. In

almost all cases, the trap monitor voltage values from the DAS were recorded

after each run (as a convenient means of comparing the changes in water level in

the traps as indicated by the DAS against level changes observed on the trap

piezometers). The traps were not filled between runs, so the value recorded by

the DAS after the fourth run corresponded to the cumulative trap-seal reduction

determined visually from the piezometer, within the limits of resolution of the

depth measurement electrode pins in the traps.

In the D and F houses, tests were first run with the vent terminal open, and

then with it taped shut, in accordance with the plan indicated in table 6. If

the first run produced a trap-seal reduction of more than 25 mm with the terminal closed, the fixtures were refilled after each run. The four values of

trap-seal reduction obtained in this way yielded an average "single-run" dH, as depicted in figure 14.

In all six of the houses, gate valves were installed in the vent lines of the

floor drain (F6 figures 9, 10, and 11). These were shut before the preoccupancy

20
tests. In the original test plan (see table 6), tests were to be made with the

floor drain vent valve both closed and open. Tests were first run with the

valve closed. Because of the small floor drain trap-seal reductions observed,

the series was not repeated with the valve open. These valves remained closed

after occupancy.

The piezometers used for the preoccupancy tests were removed before occupancy

and the installed DAS system was to monitor the performance.

3.4 DATA SUMMARY AND DISCUSSION

The data tabulations presented are from the records prepared by visual/manual

readings. The pre-occupancy testing provided opportunity for check-out of

the DAS instruments and automated data compilations. The cumulative times

for pressure excursions in the over range periods were obtained from the DAS.

The precision of the visual/manual instrument readings were less than the

resolution capability of the automated systems; general agreement was found

between the sets of data compared.

3.4.1 Discharge Characteristics of Fixtures

The results of the fixture calibrations are given in tables 7 and 8. For the

waste fixtures, the average values were as follows:

Fixture Type

Discharge Duration Volume Discharge Discharge Rate

Seconds Liters (gal) Liters/second (gpm)

Lavatory 17.0 6.56 (1.73) 0.39 (6.1)

Bathtub 166.2 82.9 (21.9 ) .50 (7.9)

Kitchen Sink 29.4 37.7 (10.0 ) 1.28 (20.3)

Clothes washer 52.6 56.0 (14.8 ) 1.06 (16.9)

For the water closets in the D/a unit (see table 8), the average water

consumption per flush was 14.7 liters (3.9 gal).

3.4.2 Trap-Seal Reduction and Vent Pressure with Vent Terminal Open

The principal and typical results from the tests with the vent terminal open

are summarized in tables 9 and 10. The detailed data are given in appendix A.

In a few instances an apparent rise in temperature level appeared and are noted

by the + readings (e.g., tables A. 1.1, A. 2. 2, A. 2. 3). Such readings may occur

as a result of: positive pressures or fluctuating miniscus and inadequate time

for the system to stabilize prior to the piezometer reading; capability to rend

the miniscus wetting the wall within a limit of 1 mm or a depth probe to

2.5 mm limit (as noted in table 2); combinations of capillary effects with

dirt in the tubing introducing a small error.

21
Results of all the tests with the vent terminal open show that the

reduced-size vents provided satisfactory performance in terms of trap-seal

retention and vent pressure.

The greatest trap-seal reduction in the D house was 10 mm, in the E house 7 mm,

and in the F house 5 mm (tables 9 and A. 1.1). The greatest vent suction was

40 mm WG (E house) and the greatest vent back pressure was 20 mm WG (F house).

See table 10 and section A.l.

The greatest trap-seal reductions in the E house, 7 mm, occurred for discharges

of W1 + W2 + W3 + C5, and for W1 + W2 + LI. Of special interest in the E house

was the shared (party wall) vent serving the first floor half baths (water

closets and lavatories). For a discharge of both these water closets and one

of the lavatories, the greatest seal reduction in the trap of the idle lavatory

was only 2 mm. See table A. 1.1(B).

For the RSV installation in the F house, the largest trap-seal reduction, 5 mm,

occurred for discharges of W1 + W2 + L; W1 + W2 + Tl; and W1 + W2 + K4. See

table A. 1.1(C).

For all tests with the vent terminal open, the largest trap-seal reduction was

10 mm, in a P-trap in the D/a unit (see table A. 1.1). It it is assumed that

the seal depth of the full-trap is 50 mm, then the trap-seal retention is given

by:

P-trap-seal rentention = 100 - (100 All) = 100 - 100( 10 mm) = gQ

H 50 mm percent

This means that P-trap-seal retention was at least 80 percent after four runs (without filling of traps between runs).

A 10 mm reduction in the level of the water closet trap yielded a greater

trap-seal retention percentage because the full trap-seal depth of the

water closet was 75 mm:

WC-trap-seal rentention = 100 - (100 AH) = 100 - (100 JALiEB.) = 87

H 75 mm percent

Generally, the idle P-traps exhibited greater trap-seal reductions than the

W.C. traps. This has also been observed in other laboratory studies where idle

P-traps were subjected to transient, fluctuating suction. Probably a major

factor in this phenomenon is the relatively larger mass and inertia of the W.C.

trap, which minimizes the effect of transient pressure fluctuations such as those associated with suction.

However, in studies of high-rise systems subject to back pressure, failures of

W.C. traps have been observed near the bottom (lower floors) of the system due

to blowback while no failures of nearby P-traps occurred. Analysis of the

geometry of the respective trap types provides a plausible explanation: with

back pressure, the water head resisting air passage (blowback) is least for

22
the W.C. case because the trap seal volume on the room side is much greater than

the volume on the sewer side of the seal.

Limited measurements relating to vent pressure fluctuations were made. The DAS

could automatically record the cumulative time that the pressure was outside

the preselected range of + 0.25 kPa, the generally accepted design range for

DWV systems. The pressure values observed were within these limits in idle

trap vents for nearly all of the tests with the vent terminal open.

Because the vent pressure excursion peaks on the magnetically-coupled

differential pressure gauges were read manually, it is estimated that the

maximum error could be in excess of 0.02 kPa (2 percent of full-scale of

manufacturer's claimed accuracy). See table 2.

Studies [1,3,10] of the relationship of peak suction in the vent and the

associated trap-seal reduction under normal conditions showed that a 25 mm

cumulative trap-seal reduction occurred only when the peak transient suction in

the vent was on the order of -0.40 kPa. A similar result was found in the preoccupancy field test, based on the pressure gauge peak readings observed visually and the corresponding trap-seal reductions actually measured with the vent

terminal open.

3.4.3 Trap-Seal Reduction and Vent Pressure with Vent Terminal Closed

Data from load tests with vent terminal closed, some of which produced trapseal reductions near failure (»25 mm), presented an additional opportunity

to examine, in this critical area of unusually severe conditions, the

relationship between the traditional + 25 mm pressure criterion and the more

meaningful criterion: trap-seal reduction not exceeding 25 mm together with

the absence of adverse back pressure effects. These data are also presented in

detail in appendix A.

The data support the earlier laboratory findings that a repetitive peak suction

of 38 mm (1 1/2 in WG) is roughly comparable to a cumulative P-trap seal reduction of 25 mm (1 in WG). Also, the trap-seal failures or near-failures observed

in some instances, with closed vent terminals and heavy hydraulic loads, indicate the general desirability of keeping the vent terminals open, although this

may not be essential for every system and is dependent on system configuration

and location of fixtures.

23
Table 1. Organization and Sequence of Activities Relating to PreoCcupancy

Hydraulic Tests

I. BEFORE GROUNDBREAKING

1. Select plumbing systems to be studied and size the reduced-size vents

using design drawings submitted by sponsor.

2. Select sensors and decide scope of measurements within each test unit;

design data collection system for post-occupancy measurements; and order

equipment.

II. DURING EARLY STAGES OF CONSTRUCTION (BEFORE DRYWALL)

3. Underground cable connections to be made between units and building sewer pressure tap to be installed.

4. Assemble instrumentation and make the appropriate modifications to

"off-shelf" items.

5. Install reduced-size vents and vent pressure taps as appropriate for

as-built wet system.

6. Arrange inspection of wet system for code compliance.

7. Verify RSV sizes taking into account wet-piping field changes, and make

modifications as necessary to satisfy (6).

8. Install wiring (for individual sensors) within walls, install "hidden"

traps (laundry, bathtub, shower); and install "hidden" flow switches

(laundry, bathtub, shower). Install tubing between equipment closets and

pressure taps in the vent system.

III. DURING LATER STAGES OF CONSTRUCTION (AFTER DRYWALL)

9. Install "external" traps (lavatories, kitchen sink).

10. Install DAS, connect sensor wires to transmission wires, and connect

pressure tubes to pressure gauges.

11. Check all instruments and the Data Acquisition System for operational

readiness.

IV. AFTER COMPLETION OF CONSTRUCTION (BEFORE OCCUPANCY)

12. Determine fixture discharge characteristics, install piezometers and

assemble portable probes for preoccupancy measurements of trap-seal

elevation.

13. Conduct preoccupancy tests according to test plan. Subsequently remove piezometers and portable test instrumentation in preparation for occupancy

of the housing units.

24
Table 2. Characteristics of Instruments and Purposes for Which Used

Instrument

Range or

Size of

Instrument

Utilization

Resolution

of System

In Preoccupancy Tests

Rulers /Piezometers 30 cm To measure depth of water

in fixtures and in traps

1 mm

Stopwatch 30 min To measure duration of

discharge

0.1 s

Graduated

cylinders

100, 500 ml To measure volume of

discharge of fixtures and

to calibrate larger con- tainers (2 and 4 liter

beakers, and 8 liter

bucket used for filling

fixtures)

Depth probe 1 in To measure trap-seal

reductions

0.1 in

(2 .5 mm)

In Pre- and Post-Occupancy Tests

100-channel DAS 100 channels

(25 channels

per unit) 3

To collect post-occupancy

data; also to record pressure overrange duration and

trap-seal reduction in preoccupancy tests

"single scan"

for millivolt

changes every

5 seconds

Instrumented traps

and trap printed

circuit cards

Magnetically

coupled

differential

pressure gauges

Printed circuit

timer cards

+ 2 cm to

- 7 cm**

10 cm of

water

To detect water depth in

trap

To measure time outside preselected pressure range

To measure time

5 mm

0.5 cmc

0.1 s

In Post-Occupancy Tests

Water meters 100,000 gal To measure volume of water

used

1/350 gal d

(0.011 liter)

Volume counter

card — To register water used 0.1 gald

(0.38 liter)

Magnetic flow

switches

10 cm of

water

To detect occurrence of

water flow in fixture

supply pipes

1 s d

a Four housing units could be monitored concurrently by the DAS by means of

switches but all six units were instrumented.

b Zero level = water surface level of full trap-seal.

c This was read visually during manual tests and it is estimated that the

readings made this way would be accurate to within 0.5 cm water gauge.

This is 2-1/2 times the manufacturer's claimed accuracy.

d For a flow duration greater than 5 s. Water meter resolution 1/350 gal; with

counter card 0.1 gal.

25
Table 3. Symbols for Fixtures

Symbol Fixture Location

W1 Water closet Master bathroom

LI Lavatory Master bathroom

T1 Bathtub Master bathroom

Sl a Shower stall Master bathroom

W2 Water closet Common (second) bathroom

L2 Lavatory Common (second) bathroom

T2 Bathtub Common (second) bathroom

K4 Kitchen sink Kitchen, laundry, utility

C5b Clothes washer Kitchen, laundry, utility

F6 Floor drain Kitchen, laundry, utility

a The D house had a shower stall in the master bathroom instead of a bathtub.

b A clothes washer was not furnished with these units, although laundry piping

was installed in the units. A clothes washer used in earlier NBS laboratory

tests was taken to each house in turn for the preoccupancy tests.

26
Table 4. Water Level in Waste Fixtures for Discharge Rate Measurements

Fixture Type Initial Water Level when Discharge Initiated

Lavatory Filled to overflow weir

Bathtub

Kitchen sink

Filled to 15 cm depth, measured at stopper rim

Filled to 15 cm depth, measured at stopper rim

Clothes washer Filled to level at which water is automatically shut

off and agitation begins - factory preset

27
Table 5. Guide for Selecting Test Loads for Residential Plumbing Systems

Number of Fixtures

Served by System

or Component Being

Tested

Maximum Reasonable

Operating Fixtures

Number of Concurrently

to Comprise Test Load

1 1 2-5 2*

6-12 3

13-32 4

For a two fixture system or component, also discharge each fixture individually.

28
Table 6. Plan for Testing Sequence and Certain Test Conditions in Preoccupancy

Hydraulic Tests

Sequence Conditions of Test

Status of

Gate Valve

in Floor

Drain Vent

Status of

Vent Terminal

Use of

Detergent

as an Additive

1 Closed Open In some tests

2 a Open Open In some tests

3 Closed Closed In some tests

a In conducting the tests, step 2 was omitted because satisfactory performance

was attained in step 1 with the floor drain vents closed. These vents

remained closed during both preoccupancy and post-occupancy testing.

29
Table 7. Waste Fixture Discharge Characteristics Determined from Field

Calibrations of Fixtures In Place

Fixture

Symbol

1

Volume

Liters

Duration

s Rate

Liters/

s

Volume

Liters

Duration

s Rate

Liters/s

D/a Unit^ D/b Unit

LI 6.7 17.2 0.39 6.5 17.7 0.36

L2 6.7 16.6 0.39 6.5 17.2 0.38

L3 6.9 21.9 0.31 6.5 16.4 0.39

T1 83.3 170.2 0.49 86.9 176.8 0.40

K4 39.2 31.5 1.24 38.1 28.4 1.34

E/e Unit E/f Unit

LI 6.4 14.6 0.44 6.6 17.6 0.38

L2 6.4 17.4 0.37 6.6 20.5 0.32

L3 6.6 16.8 0.39 6.7 15.7 0.42

T1 84.8 205.8 0.41 82.2 184.3 0.45

T2 75.8 195.6 0.39 82.8 152.5 0.54

F/a Unit F/b Unit

LI 6.4 14.2 0.45 6.6 15.6 0.42

L2 6.5 17.0 0.38 6.4 15.2 0.42

T1 83.8 152.6 0.55 82.8 121.7 0.68

T2 82.8 133.5 0.62 83.8 168.6 0.50

K4 36.4 28.6 1.28 37.0 29.3 1.26

All Units Tested

C5 56.0 52.6 1.06

* See table 3 for fixture symbol identification

^ Code: Capital letter indicates house type, lower case letter the module;

e.g., D house, a module = D/a unit.

30
Table 8. Water Closet Water Consumption Measured in D/a Unit

Run

Water Consumption for One Flush*

W1 W2 W3

liters (gal) Liters (gal) Liters (gal)

1 14.8 (3.9) 14.8 (3.9) 15.1 (4.0)

2 14.0 (3.7) 15.5 (4.1) 13.6 (3.6)

3 14.8 (3.9) 15.9 (4.2) 13.2 (3.5)

4 15.1 (4.0) 15.5 (4.1) 13.6 (3.6)

AVG. 14.7 (3.9) 15.4 (4.1) 13.9 (3.7)

* Values obtained from water meter readings

31
Table 9. Summary of Findings on Trap-Seal Reductions D, E, and F Houses with

Vent Terminals Open

A. Trap-seal reductions after four runs for a discharge of W1 + W2 + C5 in

the D/a unit

Test No. Lavatories and Bathtub Kitchen and Floor Design

LI mmL2 mm

L3mm

TImmT2mmK4mmF6mm

1 8 5 6 5 10 5 5

2 10 4 7 5 5 6 2.5

3* 7 3 6 5 10 4 5

4* 7 3 4 5 7.5 5 5

AVG 8 4 6 5 8 5 4

* Detergent in C5 runs 1 and 3.

B. Trap-seal reduction after four runs for two different leads in the E/e

unit

Lavatories Bathtubs Kitchen and Utility

LI L2 L3 Tl T2 K4 F6 mm mm mm mm mm mm mm

Discharge of W1 + W2 + W3 + C5

5 2 4 0 2.5 7 0

Discharge of W1 + W2 + W3

3 2 3 2 2.5 6 2

C. Trap-seal reduction after four runs for a discharge of W1 + W2 + K4b + C5

in the F/b unit

Test No. Lavatories Bathtubs Kitchen

LI L2 Tl T2 K4a mm mm mm mm mm

1 i 5 2.5 2.5 3

2 0 5 2.5 2.5 2

AVG. 1 5 2.5 2.5 3

* See table A. 1.1 for additional data.

32
Table 10. Summary of Findings on Vent Pressures in D, E, and F Houses

with Vent Terminals Open 1

Fixtures Discharged 1 Pressure Tap

Location2 and

Vent Size

Peak Pressure

Excursions

D/a Unit Tests

W1 + W2 + W3 + W5 S1U/2") -2 cm W.G.

(199 Pa)

+1/2 cm W.G.

W1 + W2 + W3 + W5 W3(3/4"

)

-1.5 cm W.G.

(149 Pa)

+1 cm W.G.

(96 Pa)

E/e Unit Tests

Wl + W2 + W3 K4( 1/2") -2 cm W.G.

(199 Pa)

+0

W3(e) + W3(f) + L3(f) L3(e,f)

and

W3 (e,f

)

(1 1/4")

-1/2 cm W.G.

(50 Pa)

+0

F/b Unit Tests

W1 + W2 + L2 LI (3/4") -1 cm W.G.

(100 Pa)

K4(a) + K4(b) K4(a,b)

(1")

-3 cm W.G.

(299 Pa)

+0

W1 + W2 + K4(b) C5 (1/2") -1 cm W.G.

(100 Pa.)

+2 cm W.G.

(199 Pa)

1 See section A.l for additional data.

2 Lower case letters in parenthesis indicate the applicable modules where party

wall DWV piping existed.

33
m

Portable Trap seal

Level Detector

Instrumented Trap and Fixture

Supply Pipe Flow Switches

Figure 12. Instrumentation and data acquisition system

34
PRESSURE

MAGNETICALLY-COUPLED

PRESSURE SWITCH-GAGE

Figure 13. Method for measurement of cumulative time outside preset

pressure range

35
CUMULATIVE dH

(Reading after final run)

Run

tsU

1 Run 2 Run

^

3 Run

^

4

Trap filled only before first run

Figure 14. Definition of trap-seal reductions for testing purposes

36

*Hh
4. CONCLUSIONS

4.1 ADEQUACY OF PERFORMANCE OF THE RSV SYSTEMS AT ANDREWS AIR FORCE BASE AND

ADEQUACY OF THE RSV CRITERIA

From the study it is concluded that:

1. The data show the adequacy of performance of properly designed and installed

RSV systems for one- and two-story residential designs connected to a standard drainage system, conforming to the criteria presented in

appendix C.

2. The RSV criteria can be successfully applied to vent design modification

from standard DWV plans for one- and two-story systems conforming to a recognized model code. The formulation of proposed code changes and/or

design/installation practices could be based upon the approach defined

and discussed in this report.

3. The data support the elimination of requirements for floor drain vents in one- and two-story residential housing designs at typical building sites.

Some current codes recognize that such vents may be omitted under specified

conditions.

4.2 COST CONSIDERATIONS

Published results from studies on the economics of RSV are limited [8]. A

review of such information available to the investigation described herein

indicated potential savings ranging up to about $150 per dwelling unit,

expressed in 1975 dollars. In many situations, RSV does in fact offer significant potential for savings. The actual extent of savings in a given situation depends on a number of factors.

4.3 RESIDUAL ISSUES AND CODE ACCEPTANCE

4.3.1 Residual Issues

Among lingering issues are: (a) what is the impact of frost closure of vent

terminals, and (b) are reduced-size dry vents really subject to a significantly greater risk of blockage than are standard size vents? If so, can opening the vents be satisfactorily accomplished through simple maintenance

procedures?

On the frost closure issue, the present recommendation is to conform to local

code requirements in minimum size of vent terminals where frost closure is

recognized as a problem with standard DWV systems. However, in the light of

the results of one study of frost closure [16] it seems this would be a significant problem only in areas with extended periods of freezing temperatures

(below 0°F (-18°C)). Even in these areas the use of materials with low therr. 1 1 conductivity, insulating shields, electrical heating or shortened extension

above the roof line could minimize closure. A "frost closure map" of the

United States based on available weather data and a model representative of

37
heat transfer in roof vents is needed as a guide for the design of roof vents

in very cold regions. Probably only a very small proportion of the U.S. would

require special precautions.

No frost closure or other types of blockage of the reduced-size vents at

Andrews Air Force Base have been observed by the investigators or reported by

the Air Force since the installations were completed more than seven years ago.

While neither of the issues appears to be highly critical if the recommended

design procedures are followed, the widespread acceptance and implementation of

RSV under plumbing codes would be expedited and enhanced if further applicable

data were to be provided. Perhaps the most straightforward and meaningful

approach would be to monitor field demonstrations, possibly in military family

housing, in accordance with a plan developed by a committee of interested

groups, and to publicize the findings.

Realization of widespread benefits from utilization of RSV depends on code

recognition of the method as an alternative, engineered design by referencing

of a uniform design procedure in the codes; the general availability (from

manufacturers) of the smaller sizes of pipe and fittings for venting at reasonable cost; and working familiarity with the method among contractors, engineers,

and inspectors.

4.3.2 Formulation of Code Changes and Generally Accepted Design Procedures

The current design procedures recommended by the American Society of Plumbing

Engineers [17], together with the material provided herein as appendix C,

should be considered by appropriate established code change committees, professional engineers and others as the basis for formulation of realistic code

changes and guidelines for the design of engineered systems employing RSV.

38
5. REFERENCES

[ 1 ] Hydraulic Performance of Full-Scale Townhouse System with Reduced-Size

Vents . National Bureau of Standards, Building Science Series BSS 60,

August 1975. M. J. Orloski and R. S. Wyly.

[2] Minimum Venting for Plumbing Systems . National Bureau of Standards Tech.

News Bulletin, May 1966.

[ 3 ] Studies of Reduced-Size Venting of Sanitary Drainage Systems in the U.S.A.

Paper 13, Proceedings of the CIB Commission W62 Symposium on Drainage and

Water Supply for Buildings, Stockholm, September 1973. R. W. Wyly and M.

J. Orloski.

[4] Laboratory Studies of the Hydraulic Performance of One-Story and

Split-Level Residential Plumbing Systems with Reduced-Size Venting . National Bureau of Standards, Building Science Series BSS 49, March 1974.

R. S. Wyly. et al.

,

[ 5 ] Performance of Reduced-Size Venting in Residential DWW Systems . NAHB

Research Foundation, Inc. Publication LR2 10-17, 1971.

[6] Guide Criteria for the Evaluation and Design of Operational Breakthrough

Housing Systems . Report 10-200, 4 volumes, National Bureau of Standards,

September 1970.

[7] Capacities of Stacks in Sanitary Drainage Systems in Buildings . National

Bureau of Standards, Monograph Series, Monog. 31, July, 1961. R. S. Wyly

and H. N. Eaton.

[8] Cost Savings from Reduced-Size Venting . Plumbing Engineer, July/August,

September/October 1977. Harold E. Marshall, et al.

Procedures for Estimating Economic Benefits and Materials Savings for

Plumbing Drainage Systems with Reduced-Size Venting . Contractor’s report

to National Bureau of Standards, 1975. Dickerson/Gladstone Associates.

[9] Performance Concepts for Water Supply and Drainage Systems in Buildings . Paper II-2. Proceedings of the CIB Commission W62 Symposium on Drainage

and Water Supply for Buildings, Washington, September 1976.

L. S. Galowin, et al.

[10] Performance Criteria and Plumbing System Design , National Bureau of

Standards Technical Note Series TN 966, August 1975. M. J. Orloski and

R. S. Wyly.

[11] Hydraulics of Gravity Drainage Systems . Paper II-l, Proceedings of the

CIB Commission WGL Symposium on Drainage and Water Supply for Buildings,

Washington, D.C. September 1976, R. S. Wyly, et al.

39
[12] The Evolution of the Performance Approach in Plumbing , Proceedings of

the First NBS/NCSBCS Joint Conference on Research and Innovation in the

Building Regulatory Process, Providence, R. I. , September 1976. R. S.

Wyly, et al.

[13] Report on Hydraulics and Pneumatics of Plumbing Drainage Systems - I. Bulletin 10. University of Iowa Studies in Engineering, 1973. F. M.

Dawson and A. A. Kalinske.

[14] Recommended Minimum Requirements for Plumbing . Report of Subcommittee on Plumbing of Building Code Committee, National Bureau of Standards, BH13,

1928, revised 1931.

[15] Performance of a Single-Stack DWV System Utilizing Low-Angle Stack-Branch

Confluence of Bottom Shunt Venting . National Bureau of Standards,

Building Science Series BSS 41, 1972. R. S. Wyly and G. C. Sherlin.

[16] Frost Closure of Roof Vents . National Bureau of Standards BMS 142, 1954.

H. N. Eaton and R. S. Wyly.

[17] Reduced Size Venting Design . ASPE Data Book, Vol. I, Sec. II, Chapter 1,

Sanitary Drainage Systems, American Society of Plumbing Engineers, 1980.

40
APPENDIX A. PREOCCUPANCY TESTS: DETAILED INFORMATION

A. 1 DATA WITH VENT TERMINAL OPEN

Tests with the vent terminal open were described and the findings summarized in

section 3.3.1. Detailed data on trap-seal reductions are presented in table

A. 1 . 1

.

With the vent terminal open, the greatest trap-seal reductions of the idle traps

after four runs with the most severe loads (see tables A. 1.1 (a), A. 1.1(b) and

A. 1.1(c)) were:

Unit Tested

Greatest Reduction

Load Trap AH

mm

D/a Wl + W2 + LI t2 10

Wl + W2 + W3 T2 10

W1 + W2 + W3 + C5 t2 10

Wl + W2 + W3 + C5 + DET t2 10

E/e Wl + W2 + LI t2 5

F/b W1 + W2 + LI t2

5

W1 + W2 + T1 t25

a The designation DET means that detergent was used in the indicated

detergent-using fixture.

The greatest trap-seal reduction observed in these tests, 10 mm, is less

than one-half of the generally accepted limit of 25 mm.

The greatest vent pressure fluctuations measured in the tests with the

vent terminal open (see table 13) were:

A-l
Unit Tested

Greatest Pressure Fluctuations (Suction)

Vent ; Size Load APmm

D/a SI ; 1/2/ 1-1/2/1/2" W1 + W2 + W3 + C5 -20

E/e Li ,2 ; 1" W1 + W2 + W3 -40

F/b K4(a,b);l" K4(a) + K4(b) -30

The maximum positive pressures observed did not exceed 25 mm.

Although one test load in the E/e unit produced an instantaneous peak suction

of 40 mm, the greatest trap-seal reduction shown for this load was only 10 mm.

In other studies, it has been found that with a repeated application of suction

to an idle trap-seal, a 25 mm cumulative trap-seal reduction may be expected

from a fluctuating, transient suction level of about 40 mm WG [1,3,10].

Therefore, the data with the vent terminal open show entirely satisfactory

trap-seal performance, with a safety factor of at least 2.5. Although two

loadings produced vent suction levels somewhat exceeding the generally accepted

level of 25 mm WG, this is not considered significant since no corresponding

excessive trap-seal reductions occurred.

A. 2 DATA WITH VENT TERMINAL CLOSED

Tests with the vent terminal closed were described briefly in section 3.3.3.

The data on trap-seal reductions and vent pressures with closed terminal are presented in tables A. 2.1, A. 2. 2, A. 2. 3, and A. 2. 4.

Analysis of the pattern of trap-seal failure associated with data presented for

the D/a unit with vent terminal closed (see table A. 2. 3) has been aided by the

construction of figure A.2.1. Twelve replicate tests were made, each test

consisting of four runs without replenishment of water in the idle trap-seals

between runs. From figure A.2.1 it is apparent that some traps were more

subject to failure than others, that there was a variance in results from test

to test, and that the cumulative number of failed traps increased with the

number of runs made. In considering these data, it should be remembered that

the vent terminal was completely closed, and the load was a severe one. In

addition, the likelihood of four successive replicate runs with the same loading

seems very remote under service conditions. Therefore, it seems that if under

service conditions the vent terminal should become fully closed, most of the

traps would be replenished after the first "run" of a particular loading,

because of the probable random composition of successive loadings. Therefore,

it might be expected that representative results would more nearly resemble

those after run 1 than after run 4. Under this condition, there was only one

A2
trap failure, L2. This occurred only once in 12 replicate tests (see table

A. 2. 3), and the failure was very marginal (27 mm vs 25 mm). The average trapseal reduction (in 12 tests) for trap L2 after the first run was 17.5 mm, a value appreciably less than the generally accepted 25 mm.

A3
Table

A.

1.1

Trap-Seal

Reduction

with

Vent

Terminal

Open

cn

g o o Q o < C < < < < < < < < < < 3 B

04

g CM *3- < < < o CM < < < < < < < < < < 3 B

GOc3 «=H 2 o o < c »=*4 *-=< < < < < < < < < < < M 3 s U3O o o m m m o o 1 o o o O o o m o m

14-4 VsO 2 • • . . • • • • • . . . • • • • § o o 04 CM CM o o o m m o m m CM m CM u

<D u

U-t o o o O

mmmm o o o o o o O o O fH 2 • • « • • • • • • • • • . • • • • 03 g o m m m o* CM 04 p* M3 m m cn m m m f—4

cn

aco

•H (3

4-1 2 c < •< < m -S' CM iO ao vO M3

m o r»*

O j g —4 3

~a

0)

m

g o o >—4 o o *—l O o M3 < < M3

m < C p>.

r-4m

0)

u

g +

CD1 o m o o o o o o m o o o O

m o m

O

a 04

g • • . • • • • • • . • • • • • • •

ca

HB o CM

m o mmm o r*. o o mm

mm

u

H 1—4

4-4

a)

i—t 3 | o < Ol CM < cn cn cn -3-

m cn -3- cn CM sf >3 cn

"OM 3 | o o CM cn iO CM < m PS. iO vO om -3- r* >3- *3-

sr

g

fa 1 o o CM cn

m cn cn o <3-m >3" < m -3- M3m < H H

fa fa Q Q + + m m m m <r

CJ o fa

u

u fa + + + + + +

cn 0)

<u

W 3

cn cn cn cn cn cn cn cn cn cn

u

u 3

4-> JZ 3 3 3 3 3 3 3 3 3 3 + + + + + + + + + + + + X O

t4 CD CM CM CM

a

CM Ol CM CM 04 CM CM CM CM Ol

fa -H

/"S 3 3 3 3 3 3 3 3 3 3 3 3 3 i + + + + + + + + + + + + + + +

cn cn •—4 *—

•H •-H -J 3 3 3 3 3 3 3 3 3 3 3 3 3 3

Test No. f-M CM cn >3-

m M3 o* 00 cr>

O CM CO

m M3

The

symbol A

indicates

an

active

(discharging)

fixture
Table

A.

1.1

Trap-Seal

Reduction

With

Vent

Terminal

Open

(continued) c

3>

01 w

>4-1

CO

0)COIOj

COu

4-1

0) i—i

T3

CbH I O

O

OO

O

O

O I I

x>I I I I -• < < <<<<< l I

(0< mN+

co CON

N

N

m

m -om CO < «4- 1 1 <u

4-i a>

CO

M

CJ CO •H

T3 C0 o o < CM CO CM 1 1 C 4-1 •H CO • "O

a) CU u si SI

mm tnm

m o 3 4-1

U . . • . • • 4-1 H

CM CM CM CM CMm < 1 1 X

u ss

•H o *

<4-1 <4-1

u

•a o

CM

m CO CM CM CM CM 1 1 bo CU C4-4

co cm co -a- co co -S’

co <5 p>* so p«» <o

CM c o

a> M-l c •H

s-/ co 4-1 4-1

'0-

m 3 3 CD

CO X

CO3 U <U 4-1 4-1 + + 4-1 o

T3 + + CO <u 3

CO <U s O 4-1 i—4

a> 00 CO CO CO

a

CM >4-1 >4-1 T-l CO <4-1

u

u 3 3 3 H T3 o 3 CO co CO C •H ai 4J sz + + + + + 3 3 "3 u. X o C 3

1-4 CO CNI CO CM CM CM CM CM + + < t4 CD Cb —-1 3 3 3 3 3 3 3 CD Q >—\

r—1

CO a> + + + + + + + (U <u O u

V-/ Xl Ul a. co CO a CO 3 3 3 3 3 3 3 3 < >s a u

CO (U SI T3 V CD H 4-1 J= CO CO • H o a

(U o H z CM CO -O’

m sO r-- ao as co x>

bOM

CO -Co

CO

<u>

•H

4-1 o

CO o

4-1 •o

4-1 o

<u TO

£33

as

0)M

0)S

CDaC0u

0)

CO«

siu

COu

0»c

0) o•

GO 0) a. 4J

CO Wi H o

4->

a

o> *o u c

•H CO

CO Q.

4-1 CO S2 U o u 0) 0) t-l X 0) 4J 5 e

CO CO

4-> SI

CO 4-1 •a

CD o c

»n4
Table

A.

1.1

Trap-Seal

Reduction

with

Vent

Terminal

Open

(continued)

cO

o

oo •

0) o H Z

| | | | | | | OOGO<<<<<<<<QO<<<

OOOO<<<<<<O<<<<<<

OOOOmmominmininOinoO • ••••••••••••••• OOOONNONNNNNONOO<l

oooo—t—4— <o<!o-<oo

hnChCChO c<o-<oo — oo

oooomooinmininmoinoino

OOOONOONNNNNONiflNm

oooomcninininm<-<-i<n4<:—

COC(nfO<!N^<!<!<!<o-<00^00

in m m

U o O

•3 + + + CO <U

<D 00 m m sr 'O' St U t-l u u 24 24 04 24 3 CO

4-J V z

u + + + + + +

•H CO + CM CM CM CM CM CM CM CM

Pt4 T-l 3 3 3 3 3 3 3 3 Q “N /—

\

JQ c0 CO + + + + + + + + V—/ V t v—/ <r -<r m <r H •H cm

24 CJ * 3 3 3 3 3 3 J 3

N vt in vO i— 00 CX> O

H N H

J J H

+ + +

-H CM CM CM j 3 3 3 3

+ + + + + N N H H H J J 3 3 3:

CM CO <f n lO N

<D143

u

X

00cH

00

CO 4=o

CO

(U>

tH

4-1 o

COc

CO

oo

<u

4-1 c0CJ •H13C

o

a

>>

00

cu 4=H

Observations

not

made

of

the

K4(a)

trap

for

tests

11

through

17,

as

indicated

by

dash

ma

rks.
Table A. 2.1 Summary of Findings on Trap-Seal Reductions 3 in D and F Houses

with Vent Terminal Closed

Unit D: Trap--seal reductions after four runs with W1 + W2 + T2 discharged

Lavatories Shower Kitchen, Laundry , Utility

LI 12 13 SI K4 C5 F6

mm mm mm mm mm mm mm

21 20 20 25 16 15 8

Unit D: Trap-seal reductions after four runs with W1 + W2 + W3 discharged

Lavatories Shower

,

Tub Kitchen, Laundry, Utility

LI 12 13 SI T2 K4 C5 F6 mm mm mm mm mm mm mm mm

45 39 29 24 25 38 28 24

Unit F/b: Trap--seal reductions^* after four runs with K4(a) + K4(b) discharged

Water Closets Lavatories Bathtubs Laundry , Utility

W1 W2 U 12 T1 T2 C5 F6 mm mm mm mm mm mm mm mm

42 44 21 12 13 22 24 c 30 44 25 2 15 18 24 c (0) d (0) (0) (0) (0) (0) (1) c

a 12 test average.

b The vent terminals of both the F/a and F/b units were closed.

c Equipment malfunction; level not read.

d Numbers in parentheses in last line are corresponding trap-seal reductions

after four runs with the vent terminal open.
Table A. 2. 2 Trap-Seal Reduction with Vent Terminal Closed

A. D/a unit 3

Idle trap-seal reductions after four runs Test

No.

Fixtures

Discharged

K4mm

13 mm

L2 mmT2mmC5mmLI mmSI mmF6mm

W1mmW2mm

W3mm

13 W1 + W2 + W3 38 29 39 25 28 45 24 24.0 Ab A A

14 W1 + W2 + K4 A 10 39 25 16 31 25 7.0 A A 11

15 W1 + W2 + W3 + K4 A 23 42 25 22 41 25 6.0 A A A

16 W1 + W2 + W3 + C5 32 29 35 25 A 36 25 6.0 A A A

17 W1 + W2 + W3 23 25 27 23 25 30 22 17.5 A A A

18 W1 + W2 + K4 A 17 30 23 16 26 21 2.0 A A 12

19 W1 + W2 + W3 + K4 A 17 30 23 16 26 21 0.0 A A A

20 W1 + W2 4* W3 + C5 26 26 31 25 A 35 25 3.0 A A A

3 F6 vent closed.

b Symbol A indicates active (discharging) fixtures. Virtually zero seal reductions occurred

in the traps of such fixtures, due to refill provided by trailing flow at the end of the

discharge.
Table A. 2. 2 Trap-Seal Reduction with Vent Terminal Closed (continued)

B. F/b Unit

Test

No.

Fixtures

Discharged

Idle trap-seal :reductions after four runs

K4(b) mm

L2

mm

T2mmC5mm

LI mmTlmmF6mmW1

mm

W2mmK4(a) mm

1 K4(b) A

a 2 0.0 0 1 0.0 0 2 2

2 K4(a) 1 7 — 6 7 0.0 12 12 A

3 C5(b) 3 2 0.0 A 1 2.5 2 3 1

4 K4(a) + K4(b) A 12 22.5 24 21 12.5 42 44 A

5 Wl + W2 + C5 +1 8 7.5 A 7 2.5 A A 4

6 W1 + W2 + C5 3 10 10.0 A 9 2.5 A A 4

7 Wl + W2 + K4 A 8 5.0 2 9 0.0 A A 4

8 Wl + W2 + K4 A 3 5.0 2 7 0.0 A A 3

9 Wl + W2 + K4 + C5 A 5 2.5 A 5 2.5 A A 2

10 Wl + W2 + K4 + C5 A 5 5.0 A 5 2.5 A A 0

11 L2 + W2 2 A 0.0 1 2 0.0 2 A -

12 W1 + W2 2 1 5.0 2 2 2.5 A A -

13 LI + W1 2 1 0.0 1 A 0.0 A 5 -

14 L2 + W1 1 A 0.0 1 0 0.0 A 3 -

15 W1 + W2 + LI 8 8 5.0 5 A 0.0 A A -

16 W1 + W2 + L2 2 A 2.5 2 4 2.5 A A -

17 W1 + W2 + T1 2 4 2.5 3 5 A A A -

18 K4(a) + K4(b) A 2 17.5 24 25 15.0 30 44 A

19 W1 + W2 + K4(b) A 15 12.5 28 15 2.5 A A 15

a Symbol A indicates active (discharging) fixtures. Virtually zero seal reductions

occurred in the traps of such fixtures.

ATable A. 2. 3 Effect on Idle Trap-Seal Reduction of Repeated

Loading without Refilling Trap6 between Runs,

with Vent Terminal Closed

Test unit: D/a Unit

Test load: W1 + W2 + T2 discharged

Idle Trap-Seal Reductions

Test

No. LI L2 L3 W3 SI K4 C5 F6 mm mm mm mm mm mm mm mm

After first run

1 16 17 16 11 17.5 12 13 12.5

2 19 18 16 10 22.5 15 15 12.5

3 20 27 17 16 18 16 14 0

4 13 13 11 5 8 11 7 0

5 20 20 18 14 18 17 16 +2.5

6 23 22 20 17 19 19 16 0

7 15 16 16 11 16 16 14 0

8 19 17 18 16 18 16 17 0

9 19 16 16 11 13 10 15 0

10 20 18 18 11 20 16 16 0

11 15 13 16 11 15 15 15 0

12 15 13 12 7 10 11 10 0 AVG 17.8 17.5 16.2 11.7 16.2 14.5 14.0 1.9

After second run

1 20 17 18 16 20 14 15 7.5

2 20 19 16 12 22.5 15 16 12.5

3 20 29 18 19 18 18 14 0

4 20 18 18 15 18 16 16 0

5 24 20 21 21 22 20 22 0

6 24 23 20 20 19 19 18 0

7 23 20 19 19 22 19 18 0

8 25 20 21 21 19 20 20 2.5

9 24 20 21 18 19 19 17 0 10 25 20 24 20 20 21 19 0

11 17 16 17 15 15 16 15 0

12 19 18 17 15 16 15 14 0 AVG 21.8 20.0 19.2 17.6 19.2 17.7 17.0 1.9

After third run

1 20 19 20 19 55.5 15 15 2.5

2 20 19 17 13 22.5 16 16 12.5

3 21 29 18 20 19 18 15 0

4 16 23 20 20 20 19 19 0

5 22 23 23 27 28 22 22 0

6 25 23 21 25 25 21 21 2.5

7 24 20 21 22 22 21 21 5 8 25 23 24 26 25 22 22 25

9 26 23 23 25 26 22 21 5.0

10 19 16 17 15 16 16 15 0

11 19 18 17 16 16 16 15 2.5 AVG 21.5 21.4 20.1 20.7 25.0 18.9 18.4 5.0

After fourth run

1 21 20 20 20 25 16 15 2.5

2 20 19 17 15 25 16 18 17.5

3 21 30 18 20 20 18 16 0

4 29 28 26 29 26 26 25 7.5

5 22 25 24 28 29 22 22 2.5

6 25 23 21 25 25 23 21 0

7 25 23 23 26 27 23 24 5

8 27 25 25 28 26 23 22 5

9 27 23 24 26 26 23 22 5 10 26 24 25 26 29 25 24 2.5

11 19 18 17 15 16 16 16 0

12 20 18 17 16 16 17 16 2.5 AVG 23.5 23.0 21.4 22.8 24.2 20.7 20.1 4.2

A-10
Table A. 2. 4 Vent Pressure Data for the D/a Unit with Vent Terminal Closed,

W1 + W2 + T2 Discharged (see also table A. 2. 3 and figure A. 2.1)

Test

Number/

Run

Number

Limit

Switch

Setting

K4 SI W3

Peak

Suction

Observed

Time

Beyond

Suction

Limit

Peak

Suction

Observed

Time

Beyond

Suction

Limit

Peak

Suction

Observed

Time

Beyond

Suction

Limit

kPa kPa s kPa s kPa s

1/1 0.45£/ b/ cj b

/

cj b/

2/ cj b

/

0.60 b

/

cj b/

3/d/ 0.50 cl 0.00 0.60 0.08 cj 0.00

4/1 c

/

0.00 0.30 0.00 cj 0.00

5/1 sJ 0.07 0.60 0.00 0.55 0.00

6/1 cj * 0.11 0.70 0.24 0.60 0.06

7/1 sJ 2.30 0.50 4.00 0.45 1.85

8/1 sJ 4.19 0.50 6.03 0.50 4.21

8/2 0.25 c_/ 3.57 0.70 4.87 0.60 3.62

9/1 cj 2.56 0.55 3.45 0.45 2.31

10/1 cj 3.37 / 0.75 3.52 0.55 3.43

10/2 cj 3.86 0.60 5.10 0.60 3.80

11/1 cj 3.33 0.50 4.47 0.45 3.07

12/1 cj 0.60 0.50 1.76 0.35 0.66

a This suction value was also observed for the clothes washer for this run.

b DAS not recording.

c Peak suction not observed.

d The first run of test 3 produced the only trap-seal reduction (L2) exceed in/

25 mm in the 12 test series.

A-l 1
PATTERN OF TRAP FAILURES

W1 + W2 + T2 DISCHARGED. D/A UNIT. VENT TERMINAL CLOSED

1 23456 7 8 9 10 11 12

1 2 345 67 89 10 11 12

RUN 1

FAILED TRAP THIS RUN

RUN 2

FAILED TRAP THIS RUN

13 PREVIOUSLY FAILED TRAP

RUN 3

FAILED TRAP THIS RUN

E3 PREVIOUSLY FAILED TRAP

RUN 4

B FAILED TRAP THIS RUN

H PREVIOUSLY FAILED TRAP

Figure A. 2.1 Pattern of trap failures with repetitive, heavy loading and

closed vent terminal

A-12
APPENDIX B. POST OCCUPANCY STUDY

B.l APPROACH AND OBJECTIVE

As indicated in foregoing sections of the report describing the preoccupancy

tests, the program was designed to monitor the performance of the plumbing

systems in a military family housing project after occupancy of the test units,

utilizing the sensors and data acquisition system described briefly in

section 3 and also shown in figures B.1.1 and B.1.2. The data acquisition

system was a medium speed, expandable system, with initial capability of storing

data from sensors at 100 points. Data were recorded on magnetic tape with a paper printout option. Scan speed was 20 channels per second for magnetic

tape recording and 5 channels per second using the printout option. The DAS

was remotely controlled and had provisions for data transmission by telephone

data lines. The system was interfaced with a computer for either control

and/or data storage purposes. Special sensing instrumentation was installed

for measuring the performance of the plumbing systems. Trap-seal depth changes

were sensed by means of electrically conductive pins inserted through the

walls of the plastic traps at 5 mm intervals of elevation. Vent pressure

changes were sensed by combination pressure switch-gages that could be preset

to maintain a closed circuit during time periods where the pressure fluctuations exceeded the preset range. See table 2 for further detail. Among parameters measured on real-time basis (clock timer data) were trap-seal changes,

the existence of vent pressures outside a preset range, occurrence of flow in

individual fixture supply pipes, volume of water delivered to the dwelling

unit and volume delivered to the water heater, and electrical energy consumed

by the water heater.

It was expected that the data obtained by the method outlined here would be

useful in future analysis and updating of existing water supply pipe sizing

procedures that have been in use for over 40 years.

The primary objectives of the post-occupancy study were:

1. To verify under the actual service conditions the adequacy of performance

of the reduced-size vents, which had been found adequate by preoccupancy

tests (described in foregoing sections of this report). In particular,

data on trap-seal reduction and vent pressure were to be compared with the

accepted plumbing standards of 1.0 inch maximum allowable trap-seal reduction and + 1.0 inch WG maximum allowable vent pressure fluctuation.

2. To correlate the measured trap-seal depth changes, the associated pressure

excursions in the vents; and the occurrence of specific fixture operations

in normal service loading by the occupants.

Other objectives were:

1. To obtain data on time distribution of water use in individual fixture

types, and on hot and cold water consumption and peak delivery rates In

individual dwelling units. From such data, characteristic periods of t i rr.«

between fixture operations on frequency of use can be derived. Such data

B-l
are essential to the rational updating of traditional procedures for the

design of water service and distribution piping, which are based on the

Hunter method.

2. To obtain energy consumption data, such as the quantity and time

distribution of energy consumed in heating water. Such data are needed

for comparison with current estimates and with recent data obtained in

civilian housing projects, as one element in the improvement of energy

management programs.

B . 2 RESULTS

Data were obtained intermittently and stored on magnetic tape, covering various

periods of time over a space of approximately 3 years. Sample analyses of the

data were made, from which it was concluded that vent pressure fluctuations

were negligible^ and trap-seal retention was adequate. Inspections of the roof

vents after a period of nearly 3 years showed no evidence of blockage. No

plumbing problems or complaints were reported to the Andrews Air Force Base

housing maintenance office that could be attributed to the existence of the

reduced-size vents. Any problems reported were for normal plumbing maintenance

or as a result of the presence of sensors installed for experimental purposes.

After about three years, the instrumented traps and the flow switches, as well as exposed wiring and tubing, were removed to restore the wet piping

systems to an unaltered condition. Where appropriate, standard plumbing and

building materials were used to replace instrumented components and to repair

damaged elements. As had been expected, deterioration of the trap pins from

electrolytic corrosion ultimately resulted in some of the traps leaking.

Because of the great quantity of data that were recorded, and because of the

need to edit the records to remove spurious data, the resources available to

the program proved inadequate to complete the reduction, analysis, and

reporting of the data. The data are retained by NBS in anticipation of some future opportunity to complete the analysis and report the detailed results.

Figures B.2.1 through B.2.8, and tables B.2.1 and B.2.2 show samples of data

extracted from the tapes, giving the distribution of hot and cold water flow

rates and consumption by fixture/outlet in two test units over a 5 day period.

1 In fact, essentially no data were obtained on the existence of vent pressures

outside the range of + 1 in W.G. By resetting the range to + 0.5 in. WG, some data were obtained. This indicated that vent pressures outside the

range + 1 in WG , the accepted norm, almost never occurred with the

reduced-size vents.

B-2
Based on the experience gained in this study, the following recommendations

are offered to future researchers:

1. It is very important to avoid the recording of nonessential data,

because a very large quantity of data is produced.

2. The parameters measured should relate directly to the corresponding

parameters addressed in plumbing codes, standards and generally

accepted design practice, and in currently accepted mathematical

models.

3. Sensors should be very carefully selected or designed to minimize

malfunction and maintenance. Preliminary field trials of candidate

sensors should be made to check their reliability and general

suitability before final selection for a research program. Sticking

flow switches caused false data storage on the magnetic tape of the

DAS and depleted the tape available for recording actual usage

events

.

Tables B.2.1 and B.2.2 give the cumulative hot and cold (and combined hot and

cold) water consumption recorded over a period of 5 days for tests units D/a and

F/a. These data also show the distribution of the water consumption of fixture

and outlet.

Figures B.2.1 through B.2.8 show the distribution of hot and cold (and combined

hot and cold) water flow rates by fixture and proportion of flow occurrences

over a period of 5 days for test units D/a and F/a.

B-3
Table

B.2.1

Water

Consumption

in

Occupied

Test

Unit

D/a

and

Distribution

by

Fixture

and

Outlet

(data

sample

covering

a5

day

period).
Table

B.2.2

Water

Consumption

in

Occupied

Test

Unit

F/a

and

Distribution

by

Fixture

and

Outlet

(data

sample

covering a5

day

period).

4-4 s m CO o rs pH pH CM pH o o O >am 9s?

<u nO CM nO o NO CM oo o m o o m rs o O o • • • • • • 9 0 0 0 0 0 0 9 O

(-1 on CO St CM CM oo ON pHO ^H NO

H

<u pH pH pH CM

Oh rH

COoH

OS3 On rs rs o 00 rs oo ON cm o o cm CM NO nD O nO CO sf o CM NO m o ON o o m St St

rH • • • • • • • 0 0 0 0 0 0 0 0 rH o CO H O CO pH oo ON rs ON ON m

CO on nO ON in St rs rs CM o CM pH rs o H CM CO pH CM pH ON

pH 3

4-1 4J X c 00 00

m o oo ON ON o o o O

O o S'?

H 3 nO CM

m o m CO

m o o o o o o ON o

u* o • • • • • • • 0 0 0 0 0 0 0 o M M oo CO rs CM CM rs CO <3- pH

0) 3 pH **H CM pH pH

-o 4-1 Oh

CO <v3 4-1 CO o

3> EC CO3 m pH

O o CM N©

O •3- o o o o o NO St

u

O rs CO

m o CO rs CM ON o o o o o st 3 iH • • • • • • • 0 0 0 0 0 0 0 0 4J rH on nO o o oo pH 'J’ ON pH

CO CO st CM NO o p=H CM o pH o 3 o pH pH CM pH pH 00

4-4 s ON NO o CO CM pH CO

m o o 00 ON o a* 3 St pH NO o rs c—H

00 CM

m o o NOm o o o • • • • • • • 0 0 0 0 0 0 0 o u M co CO CM CM CM CM NO CM NO pH 3 0) pH c=H pH co

4J Oh

CO 3

33

rHo 00 CJ 3 m rs o in pH 00

m CM o o CM CM o CM o ON o ON o ON CO pH ON o o m St o rH • • • • • • • 0 0 0 0 0 0 0 0 rH o rs o ON St o CO ON r** ON CO

CO CO CO St CM

m rs CM o CM o pH H CM St pH

So >N M M o is O P In

H

U

4J at 4-4 0) 3 3 3

CO 3 CO > •H rH r—i > -Q o > -Q o 14-1 •H •H

CO ^3 3 J=

M CO 3 X -X •H o O 3 H CO 0) 4-4 H c/a o 33 H H i-i -X J= o -X •H 3 3 JE JE -3 CO J3 -3 X o o a .3 -C rH

4-1 •H 4-4 4-4 4J CO 4-4 4-4 4-1 tH o 3 U

u 3 X CO CO CO CO 3 CO 3 3 rH o •x 3 3 3 4J •H pa pa pa pa pa pa •H tH pa P3 JE o 3 CO c/a •H 3 cn H 3 c 3 s 3 M M is c/a CJ 3 U 3

je o O o -3 0) 04 3 4J 3 O 3 3 o s s s 4-4 4-1 u 4-1 3 M 3 g u £ 4-1 Q 0 0 o CD CD 3 O 3 u § cn CO •H o o o rH eg eg 3 M <u 3 o 3 H

i4 CJu C->u S X

X (H Pi o X

Q
-©HI©

Figure B.1.1 Schematic of automatic monitoring instrumentation for

post-occupancy tests

B-6

NOTE:

NOTSHOWN

HERE.

SUCTION

AND

BACK-PRESSURE

OVER

RANGE

S^HSORS

WERE

INSTALLED

IN

SELECTED

FIXTURE

VENTS.
Figure B.1.2 Schematic of post-occupancy field data acquisition system

B-7
PROPORTION

OF

OCCURRENCES

1.0

.9

.8

.7

. 6

.5

.4-

.3

. 2-

. 1

-

oFigure B.2

I ft* ft

mimtn

• • 1 1 1 1 1 1 1

1

mniMM

iinmiii

Mllllllll

1 1 1 V 1 flaw

«i • «

1 1 • • i trill

*•1

1 1 1 1 1

i 1

1

i • 1

1 1 1

1

mu

.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

TOTAL COLD WATER FLOW RATE (gpm)

1 Distribution of cold water flow rates in master bath shower. D/a unit (data sample covering a 5 day period)

B-8
PROPORTION

OF

OCCURRENCES

1.0

.9

.8

.7

. 6

.5 -

. 4-

.3 -

-

1 1 1 < t iiii*

• mi iimi

mu i • 1 1 • iiim inn

-

f IMI

tlfVf lllll

t immif iimi

iiimiiimiti vim

viimiiiimii vim mtiiimiim inn

MMIIIIIIIIMI Mill

miim iiifiiviiiMnnm

* 1 1 > i

i

1 1 •

• 1 1 •••

util

0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

TOTAL HOT WATER FLOW RATE (gpm)

Figure B.2.2 Distribution of hot water flow rates in master bath shower, D/a

unit (data sample covering a 5 day period)

B-9
PROPORTION

OF

OCCURRENCES

1.0 -

.9 -

i

i

i .8 .

i

i

i .7 I

I

i

i

i .6 -

i

i

« .5 .

I

i1„

.4- 1

i

I

i

i .3 -

i

i

i

i

. 2- -

i

i

i

i

. 1

* ’

i

i

i O' '*

0

Figure B.2

I iimi

i • I • t

1 1 » 1

1

Mill

Mill

1 9 V t V

1 1 1 9 >

VMM

n m f

« i f i « flit*

mumu

» 9 1 1 1 till!

(till

9 1 1 1 1

• 1 M 1 1

I 1 I 1

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

COMBINED HOT AND COLD WATER FLOW RATE (gpm)

.3 Distribution of combined hot and cold water flow rates in master

bath shower, D/a unit (data sample covering a 5 day period)

B-10
PROPORTION

OF

OCCURRENCES

1.0 « 1 1 1

.9

.8

.7

. 6

.5

.4-

.3

. 2-

. 1

-

0*

UIM

* « I M

t I I I ( t I t I t HIM

UIM

UIM mu

HIM

I 1 1 I I HIM

HIM

HIM

I II If Hill

HIM

HIM

I I I I I II 1 1 I

I 1

1

1 I

I I 1

1

I HIM

I I I I HIM

HIM

HIM

HIM

Hilt

I I I I I I I I It

I I t I I I I I I I HIM

I I I M

r i 0 1.0 2.0 3.0 A .0 5.0 6.0

.1. ...... ..I..-.

7.0 8.0 9.0

COMBINED HOT AND COLD WATER FLOW RATE (gpm)

Figure B.2.4 Distribution of combined hot and cold water flow rates in

bath shower head. D/a unit (data samples covering a 5 day

common

period

)

B-Il
PROPORTION

OF

OCCURRENCES

1.0 -

.9 -

.8 .

.7

. 6

.5 -

.4- -

.3

. 2-

.r ;

0

*

1 1 1 1

1

I » I «

I

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

TOTAL COLD WATER FLOW RATE (gpm)

Figure B.2.5 Distribution of cold water flow rates in master bath shower, F/a

unit (data sample covering a 5 day period)

B-12
PROPORTION

OF

OCCURRENCES

1.0

.9

.8

.7

.6

.5

.4-

2- - iimtiiii

1111111111

iiniiiiii 1 1 1 1

•

iiiiiiim

« i » » r iiuivnti mu i> imniiif in

• nit iniMiiuiMit • *

1 1 1

1

1 1 1

1

i 1 1

1

1 1 1 1 •

• iff* i * 1 1 1 1 « 1 1 1 1 1 1 1

1

iiiiiMiiiiiiiiimiiiiii

1 1 I B 1

1 1 1 1 1 f i iMvimivivf miivtiit • fill

0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

TOTAL HOT WATER FLOW RATE (gpni)

Figure B.2.6 Distribution of hot water flow rates in master bath shower, F/a

unit (data sample covering a 5 day period)

B-13
PROPORTION

OF

OCCURRENCES

1.0

8

I

I

I .9 -

i

»J

.7

. 6 -

.5 -

. 4. :

.3

.2- -

i

i

iiiii mu

1 1 1 1

1

i

i .1- •

1 1 1

1

iiiii

i 1 1

f v i v v IIIII

i 9 • V V « i i • i i

i iiiii f • I 9 V iiiii

0

i*---

0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

COMBINED HOT AND COLD WATER FLOW RATE (gpm)

Figure B.2.7 Distribution of combined hot and cold water flow rates in master

bath shower, F/a unit (data sample covering a 5 day period)

B-14
APPENDIX C. RECOMMENDED CRITERIA AND GUIDELINES FOR THE DESIGN AND INSTALLATION

OF REDUCED-SIZE VENTS FOR ONE- AND TWO-STORY HOUSING UNITS

C.l INTRODUCTION

Standard design of sanitary drain-waste-vent (DWV) systems in accordance with

conventional plumbing code requirements provides ventilation piping as an integral part of the DWV system. The principal function of the vent piping is

to protect the trap-seals against excessive depletion from suction or against

blowing from back pressure. Other functions commonly ascribed to vent piping

include the facilitation of rapid and silent drainage from the fixtures, ventilation of gases from the public sewer or septic tank, and the minimization of

the buildup of concentrations of gases in the DWV system that may be corrosive

to some piping materials.

The variables that determine safe, economic vent design and sizing are numerous,

difficult to define, and intricately related. Among these variables are the

time dependent air flow in the DWV pipe network. The interdependence of the

drains and vents for functional adequacy, the likelihood of random simultaneous

or concurrent (overlapping) discharge of two or more fixtures, the hydraulic

discharge characteristics of the drainage from the individual fixtures, the

heights of the drainage stacks, the geometry of the drainage fittings, drain

pipe sizes, and the specific configuration of the DWV system.

Various research programs to study the hydraulics and pneumatics of DWV systems

have been conducted; some have provided semi-scientific, more or less empirical,

bases for relaxing specification of some of the stringent requirements (e.g.,

unnecessarily large stack sizes and individual venting of each and every fixture) in plumbing practice as regulated by the early plumbing codes in the

United States.

Among the mitigating effects of this research have been the gradual recognition

by codes of certain cost-saving practices such as wet venting, stack venting,

common venting, and the use of 3 inch diameter soil stacks and building drains

under many conditions. Based on a combination of research findings and empirical or practical judgments, codes have, from time-to-time , updated the requirements for sizing and configuration of vent systems. Generally, this evolutionary process has resulted in requirements less restrictive than they were before

the research was conducted. However, many codes still require a considerable

amount of ventilation piping, undoubtedly more than necessary for many systems.

In the 1960s and 1970s feasibility studies were conducted, in response to

interest and support by home builders and by family housing branches of the

agencies of the U.S. Department of Defense, to reduce the minimum sizes of dry

vents prescribed by codes, as they might relate to one- and two-story residential systems. It was hypothesized that size reductions for such systems might

be based on initial considerations as follows:

1. Traditional criteria for sizing main vents (stack vents and vent

stacks) were derived from research data obtained under hydraulic test

C-l
conditions which were more severe than those normally occuring in

actual service, especially in one- and two-story residential buildings.

2. The traditional criteria for sizing fixture vents and branch vents were purely empirical and based on practical experience and collective

opinion.

3. Analysis indicated that air flow demands in the vents of the DWV

systems of one- and two-story buildings are substantially less than

those provided for by the prescriptive sizing requirements of

plumbing codes.

4. Traditional criteria were based on the assumption that a substantial

diameter reduction in vent pipes occurred during service from the

accumulation of corrosion products. With pipe materials not

significantly subject to corrosion the assumption can be challenged.

The results of the several RSV studies have confirmed the hypothesis that

reduced-size vents may perform adequately and have provided certain new design

criteria and installation guidelines to facilitate the utilization of reducedsize venting as a viable technique.

In reduced-size venting design, trap-seal retention and absence of blow-back

is the criterion of performance rather than suction and back pressure. When

the application of RSV is limited to specific conditions, significant savings

in piping can be made, with safety and health still maintained.

The magnitude of savings obtainable is affected significantly by the total

length of pipe and the number and types of fittings. In general, it can also

be stated that it costs less to use small piping than to use large piping, if

factors other than size are assumed equal.

Among the principal variables affecting the cost of any system are the

following:

1 . Relative locations and positioning of the fixtures and appliances .

The following design objectives should be sought, where possible, so

as to minimize costs:

(a) the fixtures and appliances should be grouped to limit the number

of fittings and the amount of horizontal piping.

(b) where possible, the design should provide for back-to-back

bathrooms.

(c) In two-story systems, an attempt should be made to place bathrooms

and plumbing walls one above the other ("stacked").

2. Complexity of the vent system .

The system configuration and amount of piping is affected by code

requirements on venting. For example, stack venting and wet venting

C-2
designs provide for simpler configurations and less piping than

individual venting.

3 . Field changes .

The nature and extent of field changes can affect overall costs

significantly. In general, field changes should be made only in

response to architectural or site constraints, to reduce complexity

and/or the amount of piping, or to avoid inadvertant violation of the

code.

4. Cost estimating procedures used by the plumbing contractor .

There appears to be wide differences by different contractors in the

variables they consider and in their procedures for taking the variables into account in estimating costs for an installed system.

Thus, cost estimates may vary considerably between contractors, and

experience suggests this variability may be accentuated when an innovative design is presented.

C.2 GENERAL LIMITATIONS

Reduced-size venting considerations herein have been limited to DWV system

elements where (1) the waterfall distance from fixtures through their stacks or vertical waste pipes to the next lower vented horizontal drain (building drain

or horizontal fixture branch drain) does not exceed 18 ft^, (2) to residential

occupancies and (3) to residential-type fixtures.

This would limit RSV to systems or components with a maximum of three floors of

plumbing fixtures with connections distributed over a vertical distance not

exceeding 18 ft. This would generally include all one-story residences with

or without basements or crawl spaces, most split level designs, and two-story

Colonial designs conforming to the 18 ft distribution rule. This would preclude RSV in two-story designs with full basement and sewer below basement in

which plumbing connections are made in each of the three branch intervals to

a stack running the full height of the building.

Reduced-size venting is limited to DWV systems, the wet-piping of which fully

complies with the applicable plumbing code, and the dry vent system configuration and general design of which fully complies with the applicable plumbing

code with the exception of sizing.

1 Applications to systems of greater height may be feasible if adequate

provision is made for pipe and fitting friction losses in design. Preliminary research in this area has provided encouragement. (See item 3 in C.7.)

C-3
Reduced-size vents sized in accordance with C.4 shall be made of corrosionresisting materials, such as copper or approved thermoplastics .

Reduced-size vents shall not be used for fixture and stack vents below an elevation 6 inches above the flood rim of the highest fixture served by the

vent, nor for any portion of a vent subject to intermittent wetting; e.g., by

water rise due to a drain blockage or pressure that could be exerted by a pumped discharge.

See Section C.5 for important installation guidelines for reduced-size venting.

C.3 PRELIMINARY DATA

In considering the utilization of reduced-size venting, it is essential that

the proponent (designer, contractor, builder, etc) consult with the local

plumbing code enforcement agency, or other governmental department having

jurisdiction before designing the system. This is essential for assuring

that this sizing method will be acceptable under the applicable ordinance and

to ascertain what plans, specifications, and other information may be required

by the Administrative Authority prior to granting approval.

In resizing standard dry vent systems in accordance with the specific

procedures given in section C.4, certain preliminary data should be obtained

before applying the RSV criteria. Among these are the following:

1 . Site and Geographic Conditions

The likelihood of abnormal pressures in and surcharging (overloading)

of the public sewer should be estimated based on consultation with the

local sewer authority. Where surcharged sewers are known to occur frequently RSV sizing may be increased by one pipe size to provide

additional venting capacity. Under intermittent surcharged sewer conditions at infrequent intervals relief may be provided from man

hole venting, or increased for each ten living units (at continuous

site locations) as discussed in C.5. Also, the incidence of frost

closure of vent terminals should be evaluated based on discussions

with the Administrative Authority for plumbing and with local plumbing

contractors who have had some period of experience in the particular

^ For materials subject to corrosion, prudent allowances for gradual diameter

reduction would have to be made. Recommendations for such allowances have

not been developed.

C-4
geographical area. Weather records^, ASHRAE criteria^ and other

available data^ may be helpful in estimating the likelihood of

frost closure. Vent terminals should probably be enlarged in accordance with the local plumbing code in localities having minimum winter

design temperatures of less than 0°F (97-1/2 percent Column of the

ASHRAE Criterion for the time during December, January, and February).

The critical areas in which frost closure is likely, according to

this criterion, are largely in some portions of the Northern Rocky

Mountains, upper Midwest and upper New England.

2. Piping Materials and Standard DWV Design Data

Since the RSV design procedures are intended for application to

standard plumbing plans and specifications, a set of such plans

and specifications acceptable to or approved by the Administrative

Authority should be reviewed, together with the applicable plumbing

code or portions thereof, as a basis for applying the RSV criteria.

Among the types of information that should be obtained from this

review are the following:

a) Piping materials and joining methods, specified and alternate

materials and methods that may be acceptable as well as any

specifications relating to installation procedures.

b) Specific physical arrangements of fixtures and DWV piping,

as indicated particularly by plan drawings showing the

locations of all plumbing fixtures and by isometric

schematics showing the proposed arrangement and sizing of the

DWV piping (both wet and dry elements) which is acceptable as standard by the code.

C . 4 S IZ ING PROCEDURE

C.4.1 Activity Sequence and Sizing Criteria

A logical sequence of steps should be employed in modifying standard plans and

specifications for the dry vents of sanitary DWV systems. The following

sequence is suggested:

2 Evaluated Weather Data for Cooling Equipment Design, 1963 and Addendum No. 1 Summer and Winter Data , Fluor Products Company, Santa Rosa, Calif., 1964.

Engineering Weather Data, Army, Navy, and Air Force Manual TM 5-785, 1963.

3 Weather Data and Design Conditions . ASHRAE Handbook of Fundamentals, Chapter

33, Table 1, Climatic Conditions for United States and Canada, American

Society of Heating, Refrigerating and Air Conditioning Engineers, 1972.

^ Part 3, Technical Section . National Plumbing Code Handbook, McGraw Hill,

1957. Frost Closure of Roof Vents. National Bureau of Standards BMS 142,

1954.

C-5
1. Obtain preliminary data on site and geographic conditions, piping

materials, and specific plans and specifications for a standard DWV

design acceptable to or approved by the Administrative Authority

(see section C.3). Based on these data, review the general limitations applicable to RSV (see section C.2) before proceeding to

step 2.

2. Prepare isometric schematics showing DWV piping arrangements, fixture

unit loads and pipe sizes in accordance with the following procedure:

a) Label each dry vent with a letter designation, and the fixture

unit load served according to table C.4.1. Then determine the

appropriate classification of each dry vent: (1) individual or common fixture vent, or waste stack vent, (2) soil stack vent,

(3) branch vent or vent header, if any, and (4) vent stack, if

any.

b) Label each dry vent with the appropriate size determined in

accordance with the following sequence and criteria:

(i) Fixture and stack vents - table C.4.2.

(ii) Branch vents, beginning with elements connected to the

fixture vents most distant from and proceeding toward the

main vent, according to tables C.4.3, C.4.4, and C.4.5.

(iii) Vent stacks - table C.4.6.

(iv) Vent headers - size as a branch vent, considering each

element connecting to the header as a fixture vent,

according to tables C.4.3, C.4.4, and C.4.5.

(v) Vent terminals - if frost closure is likely in accordance

with preliminary data (section C.3), size according to the

requirements of the applicable plumbing code.

c) Label all wet-pipe (drainage) elements with the appropriate

standard sizes approved by or acceptable to the Administrative

Authority.

C.4.2 Illustrative Examples

Case 1 . Assume a two-story townhouse design, figure C.4.1, that has been

determined acceptable under the applicable plumbing code. Preliminary investigation reveals that PVC plastic is acceptable for all DWV pipe and fittings,

and that sewer surcharging and frost closure is unlikely, based on site

conditions, geographical location, and local experience.

To apply the RSV sizing criteria, each dry vent is labeled with a letter

designation, and classified and sized as illustrated in table C.4.7. The loads

C-6
served and the RSV sizes are then transferred to the schematic (figure C.4.2).

Both standard and reduced-sizes may be shown here for comparison if desired.

Summarizing, table C.4.7 and figure C.4.2 show the results of the classification

and sizing of the dry vents according to the RSV criteria.

Case 2 . Assume a one-story slab-on-grade ranch house design, figure C.4.3,

that has been determined acceptable under the applicable plumbing code. Other

assumptions are as in case 1.

Table C.4.8 and figure C.4.4 show the results of the classification and sizing

of the dry vents according to the RSV criteria.

The system shown in figures C.4.3 and C.4.4 requires five roof penetrations for

the five vents. A vent header might provide some overall cost reduction and

certainly would improve the appearance of the roof line. Table C.4.9 and figure

C.4.5 show the results of the application of the RSV criteria (table C.4.3) to

the sizing of the vent header.

C.5 INSTALLATION GUIDELINES AND DATA FOR BUILDING OWNER

The plumbing designer should maintain close contact with the installing

contractor before and during installation of the DWV system. The designer

should explain the special requirements of the reduced-size venting method to

the installer, who may be unfamiliar with them. To facilitate understanding

by the installer, the designer should review the basic design drawings and

specifications with the installer and when necessary to describe the system

fully, should provide more detailed drawings. This can enhance the potential

economies and level of performance obtainable from RSV installations.

The designer should make regular field inspections to be sure that the design

conditions are met. This is particularly important in the event field changes

are introduced by the contractor (as is often done for legitimate reasons in

typical plumbing work). The designer's early cognizance and review of the

plans for field changes is essential to assure conformance of the field changes

with the RSV criteria, and to assure that any RSV design changes necessitated

by the field piping changes are made in a timely fashion.

The owner should be given copies of the plumbing drawings for permanent record

so that any future additions can be properly designed and sized, and that the

location of all piping elements and drain cleanouts can be readily determined

in the event future maintenance, repairs or remodeling should be required.

Ideally, this coordination between installer and designer should be employed in

all plumbing work, not just for RSV. However, plumbing contractors are generally quite familiar with traditional code approved designs, so that the

need for close monitoring of the installation process is reduced in comparison

with that required for innovative designs.

In relation to installation requirements, the designer and the installing

contractor should be familiar with the general limitations given in section C.2,

C-7
so that compliance will be assured in the field. The following detailed

guidelines should be reviewed by both designer and installer.

If single bowl kitchen sinks (or double bowl sinks with separate traps and waste

pipes) are equipped with food waste grinders, the shutoff head of the grinder

unit, in height of water column, should be ascertained. The sink vent serving

the compartment with the grinder should not be reduced in size below an elevation 6 inches (15 centimeters) above the level corresponding to the shutoff

head of the unit.

This limitation does not apply to a grinder in a double-bowl sink with a single

trap and waste. A similar precaution should be observed in relation to any

fixture with a pumped discharge not having a drain air gap or air break.

Because most dishwashers and clothes washers are installed with a drain air gap

or break, they do not usually pose a potential problem in this respect.

The DWV system design should be reviewed to evaluate the possibility of sewage

rising into any of the vents in case of a typical drain blockage occurring anywhere in the system followed by the discharge of fixtures. In most cases, it

will be apparent that the rise in a given vent will be limited to the flood rim

level of a particular fixture. No portion of a vent at an elevation up to

6 inches (15 cm) above the floor rim level or any higher elevation that could

be wetted from such occurrences should be reduced in size.

Since reduced-size vents may not be suitable for the entry of standard drain

cleaning tools, care should be taken to assure that drain cleanouts or cleanout equivalents are adequate to assure compliance with the cleanout

requirements of the code.

In the selection of fittings for size reduction, the most economical available

fitting or combination of fittings should be used. Generally, the fewest

number of fittings should be used that will accomplish the necessary size

reductions.

Pipe and fittings customarily used in DWV work are not now manufactured in

sizes less than 1-1/4 inches. In sizes of 1 inch and less, therefore, it will

be necessary to use pipe and fittings manufactured for other applications,

such as water supply; for example, type M copper tube, or SDR PR or Schedule 40

PVC plastic pressure pipe. Probably DWV type fittings would be manufactured in

these small sizes if RSV design becomes more generally accepted In plumbing

codes and were more widely specified.

Care should be taken to follow the recommendations and specifications of the

applicable manufacturers for the design, selection and installation of joints

and joining materials.

Requirements for pitch and support of reduced-size vent piping are identical

to those for standard venting, except that closer support spacing for horizontal runs of the sizes smaller than 1 1/4 in may be required in accordance with

the pipe manufacturer's recommendations since standard venting does not

recognize nor specify support spacing for such smaller vent sizes.

C-8
Vent terminals of 1 inch size and less should be fitted with durable, corrosion

resistant, enlarged screen caps of 1/8 to 3/16 inch mesh having an open area

at least 150 percent of that of the terminal. Where approved by the Administrative Authority, vents may terminate through a wall or beneath an overhang,

provided that the end is turned down and that such terminals are located at

least 2 feet above any openable window, door, or ventilation opening within 10

feet horizontally, and are located at least 10 feet horizontally from the

property line except for adjacent townhouse units. No vent shall terminate in

a wall space, floor-ceiling cavity, or attic.

Vent terminals in frost closure prone localities shall be sized according to

the requirements of the applicable plumbing code. However, the preliminary

evaluation of the likelihood of frost closure in a particular geographic area

(see section C.3) may provide a basis for a waiver on this requirement.

In tract housing, or townhouse rows in which RSV is planned for all the units, a soil stack should extend full size to the atmosphere for each ten living units

or fraction thereof exceeding four units connected to the street sewer between

sewer manholes. This full size stack should be for the unit furthermost downstream in each ten such units or fraction thereof exceeding four units.

C.6 APPROVAL OF RSV DESIGN

The designer should assemble and organize the information required by the

Administrative Authority, using an acceptable or agreed-upon format. The

designer should be available to review this information with the Administrative

Authority. Generally, this would include drawings and specifications relating

to the RSV design. Other data may be requested by the Administrative Authority

and the designer should prepare such data as a part of the submittal. If this

supplemental data will be required, this fact should be ascertained from the

preliminary discussion with the Administrative Authority (section C.3).

C.7 CHRONOLOGICAL BIBLIOGRAPHY ON RSV

1. Minimum Venting for Plumbing Systems . National Bureau of Standards Tech.

News Bulletin, May 1966.

2 . Performance of Reduced-Size Venting in Residential DWV Systems . NAHB

Research Foundation, Inc. Publication LR210-17, 1971.

3. An Investigation of the Adequacy of Performance of Reduced-Size Vents

Installed on a Ten-Story Drain, Waste and Vent System . Stevens Institute

of Technology Report SIT-DL-73-1708 , July, 1973. T. Jackson and T. P.

Konen

.

4.

Studies of Reduced-Size Venting of Sanitary Drainage Systems in the U.S.A.

Paper 13, Proceedings of the CIB Commission W62 Symposium On Drainage and

Water Supply for Buildings, Stockholm, September 1973. R. S. Wyly and

M. J. Orloski.

C-9
5 . Laboratory Studies of the Hydraulic Performance of One-Story and

Split-Level Residential Plumbing Systems with Reduced-Size Venting . National Bureau of Standards Building Science Series BSS 49, March 1974.

R. S. Wyly, et al.

6. Hydraulic Performance of a Full-Scale Townhouse System with Reduced-Size

Vents . National Bureau of Standards Building Science Series BSS 60,

August 1975. M. J. Orloski and R. S. Wyly.

7 . Procedures for Estimating Economic Benefits and Materials Savings for

Plumbing Drainage Systems with Reduced-Size Venting . Contractor's report

to National Bureau of Standards, 1975. Dickerson/Gladstone Associates.

8. The Evolution of the Performance Approach in Plumbing . NBS Special

Publication 473, Proceedings of the First NBS/NCSBCS Joint Conference on Research and Innovation in the Building Regulatory Process, Providence,

R. I., September 1976. R. S. Wyly, et al.

9. Potential Savings from Using Reduced-Size Venting on the United States . NBS Special Publication 553, Proceedings, CIB Commission W62 Symposium,

Washington, September 1976. H. E. Marshall, et al.

10. All's Well that Vents Well — Pre-Occupancy Performance of Field Units

with Reduced-Size Vents . Yearbook of the American Society of Sanitary

Engineering, 1976. M. J. Orloski.

1 1 . Economic Aspects of the Installation of Reduced-Size Vents and Various

Standard Venting . Contractor's report to National Bureau of Standards,

1976. George Kauffman.

12. Cost Savings from Reduced-Size Venting . Plumbing Engineer, July-August

and September/October 1977. Harold E. Marshall, et al.

13. Reduced Size Venting Design . Plumbing Engineer, May/June 1978. E.

Brownstein.

14. Performance Criteria and Plumbing System Design . National Bureau of

Standards Technical Note Series TN 966, August 1978. M. J. Orloski and

R. S. Wyly.

15. Reduced-Size Venting Design . ASPE Data Book, Vol. 1 Fundamentals of

Plumbing Design, Section II, Chapter 1, Sanitary Drainage Systems, 1979-80;

also Vol. 1, Sec. II, Chapter 17, Vents and Venting, 1983-84, American

Society of Plumbing Engineers.

C-10
Table C.4.1 Drainage Fixture Unit Load Ratings For Various Plumbing Fixtures

Drainage Fixture

Fixture or Group Units (dfu)

Bathtub with or without shower head 2

Clothes washer standpipe 3

Dishwasher on separate trap 2

Floor drain 2

Kitchen sink only or kitchen sink

with food waste grinder 2

Kitchen sink with dishwasher and

with or without food waste grinder 3

Laundry tub 2

Lavatory 1

Show stall 2

Water closet 4

Bathroom group 6

Half-bath group 4

Laundry group 4

1 These are suggested ratings, subject to change from plumbing code

modifications resulting from amendment procedures. It is believed that the

RSV criteria will remain valid with modest changes in fixture unit ratings

from the values suggested here.

C-ll
Table C.4.2 Minimum Sizes for Individual and Common Fixture Vents and

for Stack Vents

Water Fall Load Served

Distance* by Vent^ Vent Size

Type of Vent (ft) (dfu) (in)

Individual fixture vent up to 8 3 and less 1/2

4 3/4

over 8 3 and less 3/4

through 18

4 1

Common fixture vent up to 8 3 and less 3/4 or waste stack vent

over 8

4 through 6 1

through 18 6 and less 1

Soil stack vent up to 8 6 and less 1

7 through 15 1-1/4

15 through 30 1-1/2

over 8 6 and less 1-1/4

through 18

7 through 15 1-1/2

16 through 30 2

* The vertical distance the water from the highest fixture (served by the

vent) falls before being diverted by the first vented horizontal drain

in its path, i.e., a vented horizontal branch drain or the building drain.

2 Fixture unit loadings for the usual fixtures are given in table C.4.1.

3 Increase one pipe size over listed value if vent length exceeds 25 ft.

C-12
Number of Fixture

Vents Served

Table C.4.3 Minimum Sizes for Branch Vents *

Rule for Sizing^

Two One pipe size larger than the largest fixture

vent served

Three

Four or more

Usually one pipe size larger than the largest

fixture vent served; exceptions requiring a two pipe size increase given in table C.4.4.

Compute from the formula

AB- Ski X /EAVS

Where Ag = minimum cross sectional area of

branch vent, Al = area of largest fixture

vent served by branch vent , and EAVS = sum

of areas of all fixture vent served by branch

vent. See table C.4.5 for cross sectional

areas for various nominal pipe sizes.

1 To apply procedure to vent headers, consider each vent connected to header as

a fixture vent and size header as a branch vent.

^ A branch vent need not be larger than would be required by table C.4.6 for a vent stack serving a DWV system with the same total fixture unit loading as the system for which the branch vent is being sized.

C-13
Table C.4.4 Combinations of Three Fixture Vent Sizes Requiring a Branch Vent

Two Pipe Sizes Larger than Largest Fixture Vent Served by Branch

Vent 1

Sizes of the Three Fixture

by Branch Vent

Vents Served Branch Vent Size

Required^

Largest Intermediate Smallest

in in in in

1 1 1 1-1/2

1-1/4 1 3/4 2

1-1/4 1 1 2

1-1/4 1-1/4 3/4 2

1-1/4 1-1/4 1 2

1-1/4 1-1/4 1-1/4 2

1-1/2 1-1/2 1-1/4 3

1-1/2 1-1/2 1-1/2 3

^ All other likely combinations of three fixture vent sizes require a branch

vent one pipe size larger than the largest fixture vent served by branch

vent

.

2 A branch vent need not be larger than would be required by table C.4.6 for

a vent stack serving a similar DWV system with the same total fixture unit

C-14
Table C.4.5 Internal Cross Sectional Areas of Various Nominal Sizes of

Pipe

Nominal

Diameter

Internal Cross-Sectional Areas 3

Schedule 40 Pipe

Metallic or Non-Matallic

Copper

Typ e M

Tube

Type DWY

in in2 in2 in2

1/2 0.304 0.254

3/4 .533 .517

1 .864 .874

1-1/4 1.495 1.317

1-1/2 2.036 1.865

2 3.355 3.272

3 7.393 7.235

a Areas for other piping materials and wall thicknesses may be obtained or calculated from the respective ASTM Standards or the manufacturers'

specifications

.

C-l 5
Table C.4.6 Minimum Sizes and Maximum Lengths for Vent Stacks

Total Load on Soil or Waste

Stack Served by Vent Stack

(dfu)

Length of Vent

Stack

(ft)

Minimum size of*

Vent Stack Size

(in)

10 and less 36 and less 1-1/4

10 and less 37 or more 1-1/2

1 1 through 30 30 and less 1-1/4

1 1 through 30 31 or more 1-1/2

1 Increase one pipe size if frequent flooded sewer conditions are anticipated.

C-16
Table C.4.7 Classification and Sizing of Dry Vents (Figure C.4.2, Example 1)

Letter

Designation

Vent

Classification

Applicable

RSV

Criterion

Fixture

Unit Load

Served

Wall

Fall

Distance

(ft)

Std

.

Size

(in)

RSV

Size

(in)

Reduction

(Pipe

Sizes)

A Waste stack vent Table C.4.2 3 2 1-1/2 3/4 3

B Individual vent Table C.4.2 1 2 1-1/4 1/2 3

C Individual vent Table C.4.2 2 2 1-1/2 1/2 4

D Individual vent Table C.4.2 2 0 1-1/2 1/2 4

E Individual vent Table C.4.2 2 1 1-1/2 1/2 4

F Individual vent Table C.4«2 2 1 1-1/2 1/2 4

G Individual vent Table C.4.2 1 2 1-1/2 1/2 4

H Soil stack vent Table C.4.2 20 10 3 2 1

I Branch vent Table C.4.3 NA NA 1-1/2 3/4 3

J Branch vent Table C.4.3 NA NA 1-1/2 3/4 3

K Branch vent Table C.4.3 NA NA 1-1/2 3/4 3

L Vent stack Table C.4.6 23 NA 2 1-1/4 2

C-17
Table C.4.8 Classification and Sizing of Dry Vents (Figure C.4.4, Example 2)

Letter

Designation

Vent

Classification

Applicable

RSV

Criterion

Fixture

Unit Load

Served

Water

Fall

Distance

(ft)

Std

.

Size

(in)

RSV

Size

(in)

Reduction

(Pipe

Sizes)

A Individual vent Table C.4.2 2 1 1-1/2 1/2 4

B Soil Stack vent Table C.4.2 8 2 2 1-1/4 2

C Individual vent Table C.4.2 2 1 1-1/2 1/2 4

D Individual vent Table C.4.2 2 0 1-1/2 1/2 4

E Individual vent Table C.4.2 2 2 1-1/2 1/2 4

F Individual vent Table C.4.2 3 2 1-1/2 1/2 4

C-18
Table C.4.9 Sizing of Vent Headers3

(Figure C.4.5, Example 2)

Header

Element

Fixture Vents

Served

al

(in2

)

SAVs (in2

)

aB

(in2

)

Nominal

Diameter

Required

(in)

G E, F 0.254 0.508 0.358 3/4

H D, E, F .254 .762 .438 3/4

I A, D, E, F .254 1.016 .509 3/4

B A, C, D, E, F .254 1.270 .570 l b

a Using rule for branch vents, table C.4.3.

b Element B was previously sized 1-1/4 in as a soil stack vent,

so will not be reduced below 1-1/4 in.

C-19
Figure C.4.1

s

S

hoiw

SteT

n

i

P

i

Ping fOC 2 ' showing

St ° ry 8lnSle family Chouse, a standard DWV design conforming to the applicable plumbing code (compare with figure C.4.2 for RSv/

C-20
Figure C.4.2 Soil-waste-vent piping for 2-story single family townhouse,

showing reduced sizes of dry vents obtainable from RSV design

criteria (compare with figure C.4.1 for standard venting)

C-21
«« ft% y-jp- ^

Figure C.4.3 Soil-waste-vent piping for 1-story single family residence,

showing a standard DWV design conforming to the applicable

plumbing code (compare with figure C.4.4 for RSV)

C-22
Figure C.4.4 Soil-waste-vent piping for 1-story single family residence,

showing reduced sizes of dry vents obtainable from RSV design

criteria (compare with figure C.4.3 for standard venting)

C-23
Figure C.4.5 Soil-waste-vent piping for 1-story single family residence,

showing the use of a vent header to reduce the number of roof

penetrations (compare with figures C.4.3 and C.4.4 showing

five penetrations)

C-24
NBS-1 14A (REV. 2-BC) U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 84-2860

2. Performing Organ. Report NoJ 3. Publication Date

4.

TITLE AND SUBTITLE

FIELD HYDRAULIC PERFORMANCE OF ONE-AND TWO-STORY RESIDENTIAL PLUMBING SYSTEMS WITH

REDUCED-SIZE VENTS

5.

AUTHOR(S)

Robert Wyly, Lawrence S. Galowin

6.

PERFORMING ORGANIZATION (If joint or other than NBS. see Instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

Tri Services

Department of Defense and

Department of Housing and Urban Development

10.

SUPPLEMENTARY NOTES

| | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document Includes a significant

bibliography or literature survey, mention it here)

This report describes hydraulic tests of drain-waste-vent systems with reducedsize vents installed in single-family housing units at Andrews Air Force Base,

Camp Springs, Maryland. The vent systems of six field units were sized according

to a procedure based on findings in prior laboratory investigations. The tests

reported were conducted on three of the units before occupancy. Principal measure- ments made were trap-seal reduction and pneumatic pressure excursions in selected

vents, using test procedures developed in the laboratory and adapted to field

conditions. Results of the preoccupancy tests showed adequate performance with

the reduced-size vents. A procedure for the design of reduced-size vent systems

is presented that should be of interest to plumbing designers and groups engaged

in updating plumbing codes.

12.

KEY WORDS (Six to twelve entries ; alphabetical order; capitalize only proper names; and separate key words by semicolon v plumbing; reduced size vents; residential plumbing; vent-system; vents

13. AVAILABILITY

| xl Unlimited

| | For Official Distribution. Do Not Release to NTIS

| | Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

(_3 Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

104

IS. Pr.ce

$ 13.00

jlCOuu OC 80 4 ) p i

'
.

'