REFERENT

UNITED STATES PARTMENT OF OMMERCE

JBLICATION BUILDING SCIENCE SERIES 41

U.S.

IIVRTMENT

OF

|»MMERCE

National

Bureau

Mf ?

172.

Performance of a

Single-Stack

DWV System

Utilizing Low-Angle

Stack-Branch Confluence

and

Bottom-Shunt Venting
The Building Science Series

The Building Science Series disseminates technical information developed at the National Bureau of Standards on

building materials, components, systems and whole structures. The Series presents research results, test methods and per- formance criteria related to the structural and environmental functions and the durability and safety characteristics of building elements and systems. These publications, similar in style and content to the NBS Building Materials and Structures Reports (1938-59),

are directed toward the manufacturing, design, construction and research segments of the building industry, stand- ards organizations and officials responsible for building codes. The material for this Series originates principally in the Building Research Division of the NBS Institute for Applied Technology. The publications are divided into three general groups: Building Systems and Processes; Health, Safety and Comfort; and Structures and Materials. Listed below are other publications in the category of

Health, Safety and Comfort

• Doors as Barriers to Fire and Smoke (C13.29/2:3) 35cents

• Field Burnout Tests of Apartment Dwelling Units (C13.29/2 :10) 25 cents

• Fire Resistance of Steel Deck Floor Assemblies (C13. 29/2:11) 25 cents

• Performance of Square-Edged Orifices and Orifice-Target Combinations as Air Mixers fC13.29/2:12) 15 cents

• Algorithms for Psychronietric Calculations (Skeleton Tables for the Thermodynamic Properties of Moist Air)

(C13.29/2:21) 55 cents ^ • Investigation of Performance Characteristics for Sanitary Plumbing Fixtures (C13.29/2:22) 70 cents

• Radiation Error in Air Ducts under Nonisothermal Conditions Using Thermocouples, Thermistors and a Resistance Thermometer (C13.29/2:26) 25 cents

• Performance of Louvered Devices as Air Mixers (C13.'29/2:27) 30 cents

Send orders (use Superintendent of Documents Catalog Nos.) with remittance to: Superintendent of Documents. U.S. Government Printing Office. Washington, D.C. 20402. Remittance from foreign countries should include an additional one-fourth of the purchase price for postage.

[See mailing list announcement on last page]
' 6 ^

H 1

Performance of a Single-Stack DWV System

Utilizing Low-Angle Stack-Branch Confluence

and Bottom Shunt Venting

Robert S. Wyly and Grover C. Sherlin

Building Research Division

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

'"fAU Of

Building Science Series 41

Nat. Bur. Stand. (U.S.), Bldg. Sci. Set. 41, 24 pages, (Apr. 1972)

CODEN: BSSNBV

Issued April 1972
Library of Congress Catalog Card Number: 74-186369

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 35 cents Stock Number 0303-0953
Table of Contents

1. Introduction 1

2. Program plan and technical objectives 2

3. Apparatus and test proced :re 3

3.1. Tests on 10-story stack 3

3.2. Selection of test loads 5

3.3. Tests on single-interval systems 7

4. Results 9

4.1. Tests on 10-story stack 9

4.1.1 Relation between trap-seal reduction and pneumatic pressure 13

4.1.2. Effects of load distribution by elevation and time sequence 15

4.1.3. Unvented offsets 15

4.2. Tests on single-interval systems 16

4.2.1. Plan-A system 16

4.2.2. Plan-B system 17

4.3. Site visits, interviews and literature review 17

5. Summary 19

6. References 20

7. Appendix 20

7.1. Supplemental details relating to experimental apparatus, test systems, and

test procedures 20

7.2. Selection of test loads 21

7.3. Evaluation of branch design finally selected 22

7.4. Optimum hydraulic properties of fixtures 22

7.5. Fouling and corrosion in DWV systems 22

7.6. The value of a follow-through research program 23

III
1

I

i

I!

II

l(

1

r.

\

k

i;

«

i:

i;
Performance of a Single-Stack DWV System Utilizing Low-Angle

Stack-Branch Confluence and Bottom Shunt Venting

Robert S. Wyly and Grover C. Sherlin

Among the more important criteria for hydraulic and pneumatic performance of sanitary drain- waste-vent systems are (1) maintenance of water seals in fixture traps, (2) limitation of pneu- matic pressures, (3) limitation of hydrostatic and hydrodynamic pressures, and (4) limitation of cross-flow between horizontal branches or trap arms. Recent tests of a single-stack drainage system proposed for a high-rise apartment project in Fairfax County, Virginia have produced the following findings with respect to these performance

criteria

:

(1) test loads (total discharge rates) ranging up to magnitudes greater than predicted loads yielded reasonable average trap-seal retention

:

(2) the use of trap-seal retention as a measure of performance appears to be more meaningful

than the traditional pneumatic-pressure measure;

(3) fitting geometry and branch arrangement can be more critical in single-stack systems than

in conventional vented systems; and

(4) present procedures for selecting test loads, for making tests, and for reporting and inter- preting measured value, need improvement and standardization. Key words: Criteria for plumbing; hydraulic test loads; performance of plumbing; single stack plumbing.

1. Introduction

Recent programs in the development of guide cri- teria for the evaluation of building systems have

evolved a consideration of the building sub-system

(built elements) in terms of several recognized

qualities or attributes of a complete building system.

Such considerations may be graphically presented in

the form of a matrix, such as shown in figure 1 which

was developed in PROJECT BREAKTHROUGH [1].^

Among the attributes shown are several that are important in the evaluation of the plumbing system as

well as of the interface between the plumbing system

and other building subsystems. To achieve the attri- butes for plumbing in a real building, adequate per- formance requirements must be stated and then in- corporated into the design and installation. One of

the performance requirements of great importance

in relation to plumbing is hydraulic adequacy or hydraulic performance, which is related primarily to

the general attribute of health and safety. Other at- tributes such as structural adequacy, durability, acoustic acceptability, and fire resistance must also be pro- vided for plumbing. Although each of these attributes could be discussed here, the scope of this presentation

will be limited to certain aspects of the hydraulic

performance of sanitary drain-waste-vent (DWV)

systems. In the design of conventional plumbing in the United States, good engineering practice and legal

code requirements have established that in multistory

^ Figures in brackets indicate the literature references at the end

of this paper.

Built

Elements

Attributes

STRUCTURAL

SERVICEABILITY

STRUCTURAL

SAFETY HEALTH

AND

SAFETY FIRESAFETY

ACOUSTIC

ENVIRONMENT ILLUMINATED ENVIRONMENT ATMOSPHERIC ENVIRONMENT

SPATIAL

CHARACTERISTICS

AND

ARRANGEMENT

1 2 3 4 5 6 7 8 9

STRUCTURE A i i

INTERIOR

SPACE

DIVIDERS

UALLS

AND DOORS. INTER-DUELLING B

UALLS

AND DOORS, INTRA-OUELLING C

aooRCEILING D

EXTERIOR ENVELOPE

UALLS, DOORS AND UINDOUS E

ROOF-CEILING,

GROUND FLOOR F

FIXTURES AND HARDWARE G

PLUMBING H i • • • • ••

MECHANICAL EQUIP- MENT. APPLIANCES

POUER. ELECTRICAL DISTRIBUTION. COhHUNICATIONS J

LIGHTING

ELEMENTS K

ENCLOSED

SPACES L

Figure 1. Matrix of performance requirements for buildings. The relative diameters of the intercept symbols

suggest relative significance of the intercepts. The

arrow indicates that this presentation is concerned with Intercept H-3.

1
buildings sanitary drainage systems must be venti- lated to the atmosphere through a separate system of piping connecting to the drainage system at appropriate points. The purpose of the ventilation system

is to minimize the pneumatic pressure excursions in the drainage system caused by the intermittent dis- charge of plumbing fixtures and appliances. Without

adequate ventilation excessive pressure excursions

would cause the water seals of the fixture and appli- ance traps to be blown or siphoned out and this action could be accompanied by the ejection of unsanitary, toxic, or malodorous waste water or sewer

gases into the building. In European practice the

ventilation provided through the upward continuation

of the drainage stack (the stack vent) to the outside

air is referred to as primary ventilation and the

ventilation provided through all other vent piping

(vent stack, branch vent, individual vents, relief vent,

etc.) is referred to as secondary ventilation. Since before World War II, several types of sani- tary DWV systems have been developed in Europe

that virtually eliminated, or greatly reduced the complexity of the traditional secondary ventilation system.

In Europe, normal plumbing loads in many buildings, particularly multistory housing, have been served

by 4-in drainage stacks utilizing only primary venti- lation to the atmosphere. Two such systems are of Swiss and British design. Recent literature describes

these and gives some test results in their design and

use [2-9].

Considerable savings in material and labor costs have been reported to be possible through the use

of a single-stack drainage system in place of a conventional system. In the United States installation of the single-stack system has been limited to a few

localities where a waiver or variance was granted

by the local plumbing authority.

The development of the experimental work re- ported herein came about as the result of a request

from Fairfax County. Virginia to make technical recommendations concerning the suitabilitv of such

a system in a particular installation. Throughout the remainder of this report the particular commercially available single-stack system used

for this study is referred to as "System X."

Although, there have been some technical reports on System X systems installed in the United States, the configuration of the system proposed for instal- lation in Fairfax County differed from those heretofore employed and the magnitude of the maximum

connected fixture load - was greater than heretofore placed on this type of system in America. Faced with

these considerations, the National Bureau of Standards recommended that tests be made to determine

whether or not the proposed system could perform i with hydraulic adequacy. The hydraulic adequacy

could be established provided the system met the functional requirements of a conventional DWV sys- tem, namely:

(1) Maintenance of a barrier against the flow

of sewer gas or foul air into the building.

(2) The provision of drainage capacity adequate

to carry away normal loads without the overflowing or ejection of waste water with- i in the premises or the backing up of waste

in idle drains or fixtures. ' Such requirements can be stated more specifically

as the following criteria that identify measurable

characteristics and thereby permit numerical comparisons:

fl) Maintenance of water seals in fixture traps, i (2) Limitation of pneumatic pressures,

(3) Limitation of hydrostatic and hydrodynamic > pressures, and

(4) Limitation of cross-flow between horizontal

branches or trap arms. A test program was developed looking toward the > evaluation of the system against the essential criteria. The project was funded jointly by the Copper De- , velopment Association and the National Bureau of Standards. The tests were carried out in the lab- oratories of the Lehrwerkstatten der Stadt Bern,

Switzerland. This organization is a well known tech- nical vocational trainins school for the building

trades, that has both the facilities and the experienced

personnel to conduct expeditious tests on sanitary

drainage systems. Arrangements for appropriate ! American materials for the tests, and authorization

for the Swiss laboratory to conduct the tests were made by technical staff of the Copper Development

Association. Staff of the Building Research Division

of the National Bureau of Standards recommended

the test procedures, monitored the tests conducted in Bern, and processed the data compiled by the Swiss i test team.

In a test program such as this, the National Bureau

of Standards would normally utilize its own facilities or monitor tests at another laboratory in this country. However, in this case the Swiss laboratory was

determined to be the only available laboratory having

both the special apparatus and the ability to produce

the reauired types of measurements in the short time

available within the schedule of this particular pro- gram.

2. Program Plan and Technical Objectives

The program plan adopted was to fl) review avail- able literature on the performance testing of and

experience with System X to obtain indications of the probable performance of the system loaded as ex- pected in the proposed application; (2) prescribe test procedures to obtain needed additional performance

data; (3) monitor actual testing in Switzerland and

interview research experts, plumbing engineers, and

others concerning the state of the art and their ex- perience with the use of System X; and (4) make

recommendations to Fairfax County.

The technical objectives and the approach employed with respect to each are summarized as follows:

' The proposal was made that a 4-inch diameter System X stack would service back-to-back bathrooms serving separate dwelling

unites on each floor of a 26-story building.

2
Self-siphonage of fixture traps.

Discussions were held with Swiss investigators

concerning this subject, and both American and

European literature were identified that provide cri- teria to guard against self-siphonage. It was not considered necessary to conduct further tests with

reference to self-siphonage.

Induced siphonage and back-pressure effects imposed on idle traps by the discharge of other

fixtures on the system.

Previous test data of American and European ori- gin were reviewed, and new tests were made on vari- ations of System X simulating the designs proposed

for the project in Fairfax County. Also, criteria were

identified relating to the control of induced siphonage

that might be caused by interaction between fixtures

in any single branch-interval.

Cross-flow of waste water from active drains into

idle horizontal drains at the junctions of two or more drains.

This aspect of cross-flow was investigated by dis- cussing the matter with Swiss engineers and technologists, by reviewing previous test data and current Swiss plumbing codes, and by making observations in a new series of tests with transparent windows in the critical reaches of the drains.

Effects of additives such as detergents, paper

diapers, and sanitary napkins on system performance.

Previous test data involving additives were re- viewed, and new tests were made that included the

three indicated additives. In the new tests, results were compared for drainage flows with and without

additives.

Service experience.

Several Swiss building projects were identified in which large service loads have been placed on these systems, and discussions were held to gain infor- mation about the general quality of performance

reported.

3. Apparatus and Test Procedures

3.1. Tests on 10-Story Stack

As described above, the facilities employed in the

tests were provided by the Lehrwerkstatten der Stadt

Bern, Switzerland.^

PRESSURE RECORDER

9 MAGNETIC-COUPLED

' PRESSURE GAGE

% I CONNECTIONS TO LARGE

I X DIAMETER MANOMETER

AND SMALL-DIAMETER

GLASS U-TUBE

LOW-ANGLE STACK- BRANCH

CONFLUENCE FITTING

P- TRAP FULL SEAL DEPTH 70 mm

WC-TRAP FULL SEAL

DEPTH 76 mm

PLUG

DEAERATOR FITTING

DOUBLE -OFFSET

FITTING

BOTTOM SHUNT VENT

Figure 2. Ten-story laboratory system used in testing for

trap-seal retention and pressure excursion caused by interactions between fixtures at different elei'a- vations on stack.

Figure 2 is a schematic of the system utilized in making the multistory stack load tests.

OPENINGS TO ATMOSPHERE

WATER TANK

CONTROL VALVE (Colibrated)

LIQUID OR POWDERED DETERGENTS QUICK-OPENING VALVE

2" TRAP ARM

I 1/2" TRAP

' Referred to as "LdSB" in following discussion.

Figure 3. Method for simulating discharge of bathtub or

lavatory, and for introducing detergents.

Figure 3 indicates the use of a plastic tank with

preset valve in its drain to simulate the discharge

from a lavatory or a bathtub. Also shown is the means employed to introduce detergents into the discharge.

Figure 4 depicts some of the instrumentation uti- lized for measuring the effects induced in idle traps

by the discharge of other fixtures on the system.

The glass tube connected to the bottom of the trap

permitted observation of the depth of residual trap

seal after application of the load, and the sensitive magnetic-coupled gage provided an estimate of the peak pneumatic pressure excursion in the trap arm

during the period of the load application. Additional

details are given in the appendix.

3
Table 1. A guide for selecting test loads for multistory plumbing systems '

Size of system

(Number of connected fixtures)

Number of concurrently operating

fixtures to comprise test load ^

t t t t t t t t t t —=0.01 —=0.02 —=0.03 —=0.04 —=0.05 —=0.06 —=0.07 —=0.08 —=0.09 —=0.10

T T T T T T T T T T

1—, Probability of overload=0.01 °

1 -15 1 -7 1 -5 1 -4 1 -3 1 -2 1 -2 1 -2 1 -2 1 1 16 -44 8 -22 6 -15 5 -11 4 -9 3 -7 3 -6 3 -5 3 -5 2 -4 2 45 -82 23 -41 16 -27 12 -21 10-16 8 -14 7 -12 6 -10 6 -9 5 -« 3 83 -128 42 -64 28 -43 22 -32 17-26 15-21 13-18 11-16 10-14 9 -13 4 129-178 65 -89 44 -60 33 -45 27-36 22-30 19-26 17-22 15-20 14-18 5 179-233 90 -116 61 -78 46 -58 37-47 31-39 27-33 23-29 21-26 19-23 6 234-291 117-145 79 -97 59 -73 48-58 40-48 34^2 30-36 27-32 24-29 7 292-351 146-175 98 -117 74 -88 59-70 49-58 43-50 37^4 33-39 30-35 8 352-413 176-206 118-138 89 -103 71-83 59-69 51-59 45-52 40-46 36-41 9 414^77 207-239 139-159 104-119 84-95 70-80 60-68 53-60 47-53 42^ 10

1 —, Probability of overload =0.001 "

1 -5 1 -2 1 -2 1 1 1 1 1 1 1 1 6 -18 3 -9 3 -6 2 -5 2 -4 2 -3 2 -3 2 2 2 2 19 -42 10 -21 7 -14 6 -10 5 -8 4 -7 4 -6 3 -5 3 -5 3 -4 3 43 -73 22 -36 15 -24 11 -18 9 -15 8 -12 7 -10 6 -9 6 -8 5 -7 4

74 -115 37 -58 25 -38 19 -29 16-23 13-19 11-16 10-14 9 -13 8 -12 5 116-152 59 -76 39 -51 30 -38 24-30 20-25 17-22 15-19 14-17 13-15 6 153-193 77 -96 52 -64 39 -48 31-39 26-32 23-28 20-24 18-21 16-19 7 194-242 97 -121 65 -81 49 -60 40-45 33-40 29-35 25-30 22-27 20-24 8 243-291 122-146 82 -97 61 -73 49-58 41^ 36-42 31-36 28-32 25-29 9 292-350 147-175 98 -117 74 -88 59-70 49-58 43-50 37-44 33-39 30-35 10 351^00 176-200 118-133 89 -100 71-80 59-67 51-57 45-50 40^ 36-40 11 401-460 201-230 134-153 101-115 81-92 68-77 58-66 51-58 45-51 41-46 12

1 —, Probability of overload=0.0001 ' T

1 1 1 1 1 1 1 1 1 1 1 2 -9 2 -4 2 -3 2 2 2 2 2 2 2 2 10 -23 5 -12 4 -8 3 -6 3 -5 3 -4 3 3 3 3 3 24 -44 13 -22 9 -15 7 -11 6 -9 5 -7 4 -6 4 -6 4 -5 4 4 45 -71 23 -36 16 -24 12 -18 10-14 8 -12 7 -10 7 -9 6 -8 5 -7 5

72 -103 37 -52 25 -34 19 -26 15-21 13-17 11-15 10-13 9 -11 8 -10 6

104-139 53 -69 35 -46 27 -35 22-28 18-23 16-20 14-17 12-15 11-14 7 140-178 70 -89 47 -59 36 -A^ 29-36 24-30 21-25 18-22 16-20 15-18 8 179-220 90 -110 60 -73 45 -55 37^ 31-37 26-31 23-27 21-24 19-22 9 221-264 111-132 74 -88 56 -66 45-53 38-44 32-38 28-33 25-29 23-26 10 265-311 133-156 89 -104 67 -78 54-62 45-52 39^ 34-39 30-35 27-31 11 312-360 157-180 105-120 79 -90 63-72 53-60 45-51 40^5 36-40 32-36 12 361-411 181-205 121-137 91 -103 73-87 61-68 52-59 46-51 41^ 37-41 13 412-463 206-231 138-154 104-116 88-93 69-77 60-66 52-58 47-51 12-46 14

^CAUTION: This table gives no guidance on the selection of particular sequences to be employed in testing with a combination of a selected number of fixtures, nor on which particular fixtures should comprise the test combination. In testing,

it has been customary to seek the "worst case" by trial and error. Research is needed to establish representative values of

t and T and to establish typical time distributions of peak use, for different types of fixtures, under service conditions.

° Computed from the Poisson probability function. The probability of occurrence of concurrent operations in excess of the number selected for a test load is computed as not greater than the indicated values for service systems not larger than

indicated by the stated load range. This probability is termed 1 in NBS BMS 65, Methods of Estimating Loads in Plumbing

.Systems. t 'The ratio t/T is the individual probability of finding a particular fixture on a service system in operation if observed at random during a typical peak-load period, and is equal to the ratio of time duration of a single operation, t, to the average time between successive operations, T, for that fixture, in the terminology of NBS. BMS 65.

4
1/4" (I D.) GLASS TUBE

MAGNETIC- COUPLED

GAGE

1 1/2" DIA

P-TRAP

« MEASURED FROM TOP OF DIP TO CROWN WEIR

Figure 4. Method for measuring trap-seal retention and peak

pressure excursions in trap arm of P-trap.

3.2 Selection of Test Loads *

One of the more difficult aspects of a hydraulic

performance evaluation of a plumbing system is the

selection of representative test loads. In choosing test loads for multistory systems, table

1 may be utilized as a guide. This table is based on

the Poisson approximation to the binominal probability theorem. It was developed at the National Bureau of Standards, using concepts similar to those

that have for some time been utilized by British in- vestigators [10, 11]. Presently, a similar but less comprehensive table appears in the British Code for Plumbing Practice [12]. Table 1 is not unreasonable

as a guide for the testing of effects between branch

intervals. Table lA is a guide for selecting test loads

to evaluate interactions between fixtures in the same

branch interval, derived from Table 1 for a probability of overload, 1/t^ = 0.01 and for a probability

of usage t/T = Q.\0. This was used in deciding upon

test loads for Plans A and B, described in section

3.3. (See also appendix 7.3)

Table 1A. A guide ' for selecting test loads for single- branch-interval portions of plumbing systems

Number of fixtures served by piping component

being tested

Number of concurrently

operating fixtures to comprise test loads

CAUTION: This table gives no guidance on the selection

of particular sequences to be employed in testing with a combination of a selected number of fixtures, nor on which particular fixtures should comprise the test combination. In

testing, it has been customary to seek the "worst case" by

trial and error. 'Also discharge each fixture individually.

Table 2, derived from table 1, shows test loads*

computed for a selected drainage system having 50

bathrooms, each containing a lavatory, a water

closet and bathtub. The objective in table 2 was to compute a realistic test load that provided a safety factor to compensate for uncertainties. The principal

variables considered in the computation are (a) the

probability of the individual fixture types being in operation during "rush hour" periods (as denoted

by the ratio t/T; (b) the level of overload risk to be utilized for design (1/^) ; (c) the types of fixtures to be assumed in peak use at the same period of the day; and (d) the vertical distribution to be utilized in introducing the separate fixture discharges comprising the test load. One possible vertical distribution of each load is shown for a back-to-back bathroom plan (two fixtures of each type on each floor) . The separate fixture discharges involved in the test load are more closely

grouped in the 10-story test facility than are fixture discharges that would be expected to occur naturally

in a 25-story stack. A review of various European

data and a discussion with European investigators

have indicated that, in laboratory tests, close-together,

near-the-top grouping results in generally greater

trap-seal reductions and pneumatic pressure excursions

than would be obtained with a wider vertical distribution. For this reason, in a service situation, the probability of occurrence of effects similar in magnitude to those produced by the loads shown in table 2 should actually be much less than the value of 1/r shown.

The fixture-use frequencies (t/T) assumed in computing loads No. 1, 2, and 3 in table 2 are the British values obtained from surveys in flats [13] rounded

to the next higher nominal values. The load distribution described in table 2 is a conservative one in which the different elements of the hydraulic load were to be introduced as close to the top of the system as possible with the apparatus that was to be provided at the LdSB. The method used for choosing the numbers of fixtures of each type to be

discharged in a mixed system emphasized providing

for the full effect of the heaviest loaders as deter- mined separately from table 1, before accounting

for simultaneous operation of other lighter-loading

fixtures assumed to be in peak use at the same period

of the day. The British data indicated that bathtubs

do not ordinarily contribute significantly to the morning peak load, hence need not be involved in simulating the morning load. Originally, British in- vestigators believed that the evening peak load for bathrooms should comprise the discharge of water

closets and bathtubs, and this assumption has been

made in table 2 in computing the types 2 and 4 loads. However, recent British findings have been interpreted

to indicate that the bathtub use is scattered over the

dix.

* Additional discussion is to be found in section 7.2 of the appen-

^ In the expression l/r, r is the Greek letter "tau".

^ At the time the test procedures were developed, the proposed

connected load was understood to be 2.5 pairs of back to-back bath- vooms serving separate dwelling units: hence the computed test loads were for a 50 bathroom system rather than a 52-bathroom

system. This is not considered a sienificant difference.

' The term is used here to refer to those fixtures producing the

greatest rates of ilischarge. For the purpose of this presentation

the characteristic discharge rate of a fixture is utilized as the measure of the "heaviness" of loading.

5
Table 2. Hydraulic test loads computed' for 50-bathroom DWV system' (to be distributed near top of 10-story test system)

Load no. and type ' Vertical distribution of load on test system for various levels of overload risk, 1/t

(A) 1/t=0.01 (B) 1/t=0.001 (C) 1/t=0.0001

1 3 WC's+l LAV 4 WC's+1 LAV 5 WC's+1 LAV

(Morning peak,

"WC's+LAV's/

worst case)

Floor No. 10

2 WC's=54 gpm for 9 s 1 LAV=10 gpm for 7.5 s

Floor No. 10

2 WC's=54 gpm for 9 s 1 LAV=10 gpm for 7.5 s

Floor No. 10

2 WC's=54 gpm for 9 s

1 LAV=:10 gpm for 7.5 s

t/T for WC=0.01

t/T for LAV=.01

Floor No. 9

1 WC=27 gpm for 9 s Floor No. 9

2 WC's=54 gpm for 9 s Floor No. 92 WC'szz54 gpm for 9 s T0TAL=91 gpm T0TAL=118 gpm

Floor No. 8

1 WC=27 gpm for 9 s TOrAL=145 gpm

2 3 WC's+5 BT's 4 WC's+6 BT's 5 WC's+6 BT's (Evening peak,

WC's+BT's

worst case)

Floor No. 10 2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 minFloor No. 10

2 WC's=54 gpm for 9 s 2 BT'sr=24 gpm for 1.7 min

Floor No. 10

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

t/T for WC—0 01 t/T for BT=.05

Floor No. 9

1 WC=27 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 9

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 9

2 WC's=54 gpm for 9 s 2 BT's=:24 gpm for 1.7 min

Floor No. 8

1 BT=12 gpm for 1.7 min

Floor No. 8

2 BT'sr=24 gpm for 1.7 min

Floor No. 8

1 WC=27 gpm for 9 s T0TAL=141 gpm TOTAL=180 gpm 2 BT's=24 gpm for 1.7 TOTAL=207 gpm

min

3 3 WC's+7 BT's+1 LAV 4 WC's+9 BT's+1 LAV 5 WC's+10 BT's+1 LAV

(Composite peak,

WC's, LAV'S,

BT's—worst case)

Floor No. 10

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

1 LAV=10 gpm for 7.5 s

Floor No. 10

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

1 LAV=10 gpm for 7.5 s

Floor No. 10

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7

1 LAV=10 gpm for 7.5 mins

t/T for WC=0.01

t/T for LAVr=.01

t/T for BT=.05

Floor No. 9

1 WC=27 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 9

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 9

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 8 2 BT's=24 gpm for 1.7 minFloor No. 8

2 BT's=24 gpm for 1.7 min

Floor No. 8

1 WC=27 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 7

1 BT=12 gpm for 1.7 min

Floor No. 7

2 BT's=24 gpm for 1.7 min

Floor No. 7

2 BT'snr24 gpm for 1.7 min

TOTAL=175 gpm

Floor No. 6

1 BT=12 gpm for 1.7 min

Floor No. 6

2 BT's=24 gpm for 1.7 min

TOTAL=226 gpm TOTAL-265 gpm

4 5 WC's+3 BT's 6 WC's+4 BT's 8 WC's+3 BT's

(Evening peak,

WC's+BT's,

worst case) t/T for WC=0.03

t/T for BT=.03

Floor No. 10

2 WC"s=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 9

2 WC's=i54 gpm for 9 s

1 BT=12 gpm for 1.7 min

Floor No. 8

1 WC=27 gpm for 9 s T0TALr=171 gpm

Floor No. 10

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 9

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 8

2 WC's=r54 gpm for 9 s TOTAL=210 gpm

Floor No. 10

2 WC's=54 gpm for 9 s 2 BT's=24 gpm for 1.7 min

Floor No. 9

2 WC's=54 gpm for 9 s 1 BT=:12 gpm for 1.7 min

Floor No. 8

2 WC"s=54 gpm for 9 s

Floor No. 7

2 WC's=54 gpm for 9 s TOTAL=252 gpm

^ Computed as described in section 3.2. The discharge rates assumed for fixtures are generally similar to those recom- mended in the National Plumbing Code Handbook, by Vincent T. Manas, (McGraw-Hill, 1953). The term "t" is the average

duration of a single discharge, and "7"' is the average time between successive uses of the fixture during the period of maximum

usage. ^Various other loads can be computed, depending on the values of t/T and on concurrence of peak usage periods for the

different types of fixtures.

' Back-to-back arrangement assumed in choosing spatial distribution of fixtures discharged together.

* Abbreviations are WC for water closet, LAV for lavatory, and BT for bathtub.

6
evening hours, and that the "evening peak" for bath- rooms may be expected to produce loads of lower

magnitude than the morning peak.

The essential steps followed in computing the loads

in table 2 were:

Loads No. 1 and No. 4

Two types of fixtures with the same value of t/T

are involved, load No. 1 will be processed first. Step 1: Consider the heaviest loaders separately;

i.e., WC's,® which in this design are 50

in number. By the use of table 1, find in the column for f/r = 0.01, the location

of the numbers that would bracket the number 50. From this location move in the same row across the table to the column that gives the "Number of con- current operating fixtures to comprise

test load."

Step 2: Consider the total number of fixtures of concern in this example (50 WC's and

50 LAVS = 100). Find in the column for t/T = QS)\ the location of the numbers

that bracket the number 100. Then in the same row move across the table to the column "Number of concurrently operating fixtures to comprise test load." Step 3: Obtain the number of non-WC fixtures

to be discharged by subtracting the number of WC's obtained in step 1 from the

total number of all fixtures to be dis- charged that was obtained in step 2. The use of table 1 is very similar for load 4 as for load 1. For step 1 the value of 50 WC's will be located

in the column where t/T = Q.O^. Likewise in step 2

the value of 100 for WC's plus BT's will be located

in the same column.

Load No. 3

Three types of fixtures with two or more different values of t/T are involved. In this type of load, it is assumed that the peak-load conditions for all fixture types involved occur at the same time of day.

Step 1: Same as step 1 for loads no. 1 and no. 4. Step 2: Based on the average value of t/T for all non-WC fixtures considered as a composite group, obtain from table 1 the total number of fixtures to be discharged from

this group.

Step 3: Consider the second-heaviest loaders sep- arately; i.e., bathtubs. For this group,

find the number to be discharged, based on its assumed value of t/T.

Step 4: Obtain the number of fixtures of the third- heaviest loading type, if any, to be dis-

" To facilitate tabular presentation of data abbreviations for fix- tures have been used as follows: WC's = Water Closets, LAVS =

Lavatories and BT's = Bathtubs.

charged, by subtracting the number ob- tained in step 3 from the number ob- tained in step 2. Load No. 2

Two types of fixtures with different values of t/T

are involved.

Step 1: Same as step 1 for loads no. 1 and no. 4.

Step 2: Based on the average value of t/T for both fixture types, find the total number

of fixtures to be discharged.

Step 3: Same as step 3 for loads no. 1 and no. 4.

It has been customary to design with a risk of overload, 1/t, of 0.01. Table 1 provides the means

for selecting loads with values of \/r of 0.01, 0.001,

and 0.0001. Table 2 gives computed loads at all three

levels. Because conventional vented 4-in systems are not designed to carry a simultaneous discharge exceeding

144 gpm based on 1/t = 0.01, it may not be reasonable to employ test discharges exceeding this value in evaluating innovative systems.

Large safety factors probably are associated with

the loads shown in tables 2 and 3 for the following

two reasons: first, the assumption that the peak load

from mixed fixtures will always include the computed

peak load from the water closet group is quite unlikely; and second, the arbitrary grouping of fixture discharges near the top of the stack would not be

representative of the normal service loading pattern

which would tend to be distributed over the height of the stack. The close-together distribution tends to produce more severe hydraulic and pneumatic effects than practically all other distributions that might be

expected to occur with natural loading. Because the stack as actually constructed and as

illustrated in figure 2 did not provide for introduction

of all the hydraulic load elements at exactly the same

elevations called for in table 2, some modifications in

vertical distribution were required. Referring to table 3 for the loads actually used in the multistory tests,

it will be seen that additional loads were tried, that included the discharge of six bathtubs, the intentional modifications in vertical distribution of loads lA and

IB, and the addition of solids or detergents to some

of the loads for comparison with clean water. Also, one new load was applied for the purpose of studying

the effect of a time delay in discharging the load

at the lower floor of a two-floor concurrent hydraulic

load.

3.3. Tests on Single-Interval Systems

Figures 5 and 6 show two arrangements of branch

piping tested for possible hydraulic and pneumatic

interactions between different fixtures on a given floor. These arrangements are designated "Plan A" and

"Plan B." These were considered the arrangements

most likely to be used in the project in Fairfax

County.

7
Table 3. Hydraulic test loads applied to 10-story system shown in figure 2

Test No. Type of load Flow

rate Additives

Vertical distribution of fixtures discharged

Floor 10 Floor 9 Floor 8 Floor 7

Equivalent

fixture-unit load "

lA *

'

IB^

IBl.B dew

IBa-o dew

1B«.5 dew

IBi.r, <] I)

IBs'O d D

IBi.r, <i 1)

IB "

IC

2A|,|,;t

2B

5

Simultaneous

Simultaneous

Simultaneous

Time-delay "

Time-delay "

Time-delay '*

Time-delay "

Time-delay

Time-delay "

Simultaneous

Simultaneous

Simultaneous

Simultaneous

Simultaneous

Simultaneous

Simultaneous

Simultaneous

Simultaneous 99

gpm

91

91

118

118

118

118

118

118

118

118

118

118

145'

141

180"

72"

72"

None

None

None

None

None

None

Paper diaper*

Paper diaper*

Paper diaper*

None

Paper diaper*

Sanitary r„ii Napkin

None

Detergent

None

None

Detergent "

None

2 WC

1 LAV

1 WC

1 LAV

2 WC

1 LAV

2 WC

1 LAV

2 WC

1 LAV

2 WC

1 LAV

2 WC(1W/D)"

1 LAV

2 WC(1W/D)

1 LAV

2 WC(1W/D)

1 LAV

1 WC

1 LAV

1 WC(W/D)

1 LAV

1 WC

1 WC

1 WC(W/D)

1 WC

1 WC

2 WC

2 WC

2 WC

2 WC

2 WC

2 WC

2 WC

1 WC

1 WC

1WC(W/SN+TP) 1WC(W/SN+TP) 1 WC

1 LAV

2 WC

1 LAV

1 WC

2 BT(1W/DET)

2 WC

2 BT

2 BT

1 WC

1 WC

2 BT

1 WC

2 BT

1 BT

2 BTflW/DET) 1 BT(W/DET)

2 BT 1 WC

1 BT

1 WC

1 BT(W/DET)

1 WC

2 BT

2 BT

2 BT

2 BT

1 WC

1 WC(W/D)

1 WC(W/SN+TP)

1 WC

1 WC

1 BT

1 BT (W/DET)

1 BT

200

200

350

350

350

350

350

350

350

350

350

350

515

487

770

245

' Identical to computed loads in table 2, except computed 9th floor load introduced at 8th floor instead.

° Load lA * is a slightly more uniform vertical distribution than lA. "Load IB* is a slightly more uniform vertical distribution than IB.

* One paper diaper, large-size, flushed in each WC indicated, without removing plastic membrane.

° One sanitary napkin, large size (SN), flushed together with toilet tissue described in 'Three loosely-wadded balls of 4 double-thickness squares of toilet tissue, (TP) in each WC indicated.

' Load is a slightly more uniform distribution than computed in table 2. 'Type 2 detergent, 3.1 ml in 200 ml water solution introduced through bathtub drain in 12 s. 'Load is a slightly more uniform vertical distribution than computed from table 1. Identical distribution to that computed in table 2. " Type 1 laundry detergent powder, 74 cc in water solution introduced through bathtub drain in 1 min. " Identical load to No. 5, except that discharge of 1 WC on 9th floor has been added. " Equivalent fixture-unit values read from Hunters curve for systems employing flush-valve WC's (see NBS, BMS 65, BMS

79), except as indicated in note 15 below.

'* Time delay of 1.5, 3.0, or 4.5 sec after discharge of 10th floor load: then 8th floor load discharged. cw=clean water, D=paper diaper, N=sanitary napkin and d=delay in seconds. "Since this load did not involve WC's, no equivalent fixture-unit load is given. However, if a value f/r=0.04 and 1/t=0.01

are assumed, a test load of 6 fixtures is obtained from table 2 for a system comprising 46-58 fixtures of a type likely to be

subject to maximum usage at a particular time of the day. Final plans called for a maximum of 52 bathtubs on each stack

in the project in Fairfax County. "Abbreviations in parentheses such as 2WC (IW/D) means two WC's were discharged (one with diaper). Similarly other abbreviations used are SN for sanitary napkin, TP for toilet paoer and DET for detergent.

8
Tables 4 and 5 describe the tests performed on

the two single-interval systems. Table 6 describes four

variations in piping arrangement tried in the tests with the Plan B system.

4. Results

4.1. Tests on 10-Story Stack

Table 7 shows for each floor the relative trap-seal retention in the 11/2 iri lavatory P-trap, for various

applied loads. Table 7A shows similar data for WC

trap-seal retentioji employing a number of time- sequence variations of a given combination of fixtures. In none of these measurements was the average reten- tion less than 56 percent of the maximum trap-seal

depth, which was 70 mm (about 2% in) for the P-trap and about 76mm (3 in) for the WC trap. Thus there was in excess of 11/4 in of average residual trap seal, even with the heaviest loads employed in obtaining the data shown.

PLAN A

1^

3" \ Layout 4 >< Only

Fitting No. 3-^^ ®

Figure 6.

Fitting No. I Layouts 2,3 and 4

Single branch-interval element. Plan "B", used in testing lor trap-seal retention and pressure excursions caused by interactions between fixtures within

the same branch interval.

I , 2 , 3 . 4 , 6 Stations for observing mnximum

deptli of water and/or pneumatic pressure in branches.

3 , 4 These stations were equipped with transpar- ent windows in top of branches.

5 This station was equipped with transparent win- dow nt heel of fittinc. for observation of flow

in 3-in waste brancli. 7 . S . 9 . 10 Magnetic-coupled pressure gages for observation of peak pressure excursions in trap arms.

II Transparent window in side of aerator fitting to permit observation of flow inside fitting.

Side (a)

Figure 5. Single-branch-interval element. Plan "A", used in testing for trap-seal retention and pressure excursion caused by interactions between fixtures within

the same branch interval.

1 , 2 Transparent windows in top of drain for ob- servation of maximum depth of water in branch.

3 , 4 Magnetic-coupled pressure gages for observation of peak pressure excursions in trap arms.

Side (a) System actuall.v tested (3-in combination

soil-and-waste branch).

Side (b) System not tested (4-in combination soil- and-waste branch).

Table 4. Description of tests made on single-interval

test system, plan

Test load number

Number

of runs Loading conditions '

Fixtures operated Material discharged

1 4 WC CW

2 3 WC CW+Paper diaper

2C* 2 WC CW-|-Paper diapter

3 4 WC-fB CW

4 WC-fB CW in both, -f Paper

diaper in WC

3 D+DET 4 WC-fB CW-fPaper diaper in WC, 0.0043 concentration Type 3 detergent in bathwater

' See figure 5 and table lA.

* Multiple-fixture loads involved simultaneous discharge of indicated fixtures: WC=water closet and B=bathtub.

' CW=clean water. Paper diaper test load involved flushing one diaper, including plastic membrane.

* This load similar to no. 2; but was more severe because

diaper was wetted, wadded into round-ball shape, and carefully placed in WC bowl in this shape just before flushing. Idle P-trap simulating lavatory trap was not refilled after the

first run, thus providing a 2-run cumulative series.

^ Subscript abbreviations are D for diaper and DET for detergent.

9
Table 5. Description of tests made on single-interval test system, plan B

'

Test

load No.

runs

Fixtures operated

Loading conditions Time sequence

Material discharged " Piping

Arrangement

1 2 Li Single-fixture load CW Layout 1 2 1 L= " cw

3 4 B, CW

4" r>Dl // cw " 3

3'DET 1

° R 0.00043 concentration type 3 detergent in bathwater

" 3

4 2 B= CW " 1 9 RJ32

/f CW 3 4^DET 2 1)2 U.UU043 concentration type 3

detergent in bathwater

0

5 4 WC, ff CW " 3

5d 4 WG " CW+Paper diaper " 3

2 WG CW+Paper diaper " 4

6 4 WG CW " 3

7 3

^

4

"

"

Simultaneous

"

"

CW

CW

CW

" 1

" 2

" 3

8 2 L,+B, Li ended discharge before Bi CW " 1

9 1 U+B, Bi ended discharge before Li CW " 1

10 1 L2+B2 L2 ended discharge before B2 CW " 1 9 L.i-|-D2 Discharges ended same time CW " 3

•'^^DET 3 L,+B= Discharges began same time 0.00043 concentration type 3 detergent in bathwater

" 3

12 4

3

WCi+WCo

Simultaneous

" CW

CW

" 3

" 4 12« 3 CW, paper diaper in WCi 3 4

// CW, paper diaper in WCi " 4

'See figure 6 and tables lA and 6. Here L=lavatory, B=bathtub and WC=water closet. 'Followed by 3 additional runs without refilling trap, yielding a 4-run cumulative seal-reduction series.

' CWrzClean water. Paper diaper, test load involved flushing diaper, including plastic membrane.

'Subscript abbreviation are D for diap^er and DET for detergent.

Table 6. Description of four variations in piping arrangement for single-interval test system, plan B}

Layout

no.

Fitting size and type ° Branch

No. 1 No. 2 No. 3 diameter

Size Type Size Type Size Type No. 1 No. 2

in in in in in

1 2x2x2 ST 3X3X3 ST 2X2X2 ST 2 3

2 3x3x2x2 LT 3X3X3 ST 2x2x2 ST 3 3

3 3X3X2X2 LT 3X3X3 ST 2x2x2 LT 3 3

4 3X3X2X2 LT 4X4X3X3 LT 2x2x2 LT 3 4

* See figure 6 and table 5. 'Short-turn (ST), short-radius pattern; or long-turn (LT), long-radius pattern.

10
Table 7. Relative trap-seal retention in 10-story stack tests resulting from loads of table 3.

Average ' relative P-trap seal retention,

Test II Floor lA lA * IB IB * IB *d' IC 5 ^DET 6

0.97 0.98 0.98 0.97 0.93 •' 0.98 0.97 0.99 ' 0.99

1.00 - 10

.98 .98 .99 .98 0.97 ' .97 .99 .96

' 0 .97^ 9

.92 .94 .90

' .93 .89 .93 .93 96 ' .96 ' .96 - 8

.91 .91 .90 .87 .81 .88 .85 .86

.87

' .87

" 7

6

.74 .71 .65 .68 .61 .64 .59 .71

.60

' .60

- 5

4

.70 .81 .62 69 .72" .56" 67' .68" .65

= 3

2

1

^ Single run only.

" Average of two runs.

" Average of three runs.

* Average of four identical runs, except where otherwise indicated.

is the relative trap-seal reduction, where "AW" is the average reduction and "//" is the full trap-seal depth.

H

° Dash-marks indicate either no data were taken, or that the data taken were irrelevant to the particular tabulation. Trapseal measurements were not obtained at floors 1, 2, 4, and 6.

' Subscripts are abbreviations of D for diaper, N for sanitary napkin, and DET for detergent.

Table 7A. Relative trap-seal retention in 10-story stack tests resulting from different time sequence variations of load IB ^

Relative WC trap-seal retention

Test load ^ Flo

IB.cw

0.98 '

IBl.sJrv

1.00

0.97

.87

.90

IB1.5.1D

0.99

0.98

.85

.91

IB,

0.99

.98

.88

.93

IBj.o.lD

1.00

0.99

.83

.89

1B^.=„

1.00

0.98

.90

.91

IB,.,

0.98

.99

.85

.90

'Loads described in table 3 (clean water and paper diapers).

° Average of 3 identical runs, except where otherwise indicated. 'AH

is the relative trap-seal reduction where "AH" is average reduction and is full trap-seal depth.

H

* Average of 4 identical runs. ^Symbols: cwr=clean water; D—diaper; s=simultaneous; d =time delay. (Example: IBt.o.id represents Load IB with a

3.0 sec time delay, with a paper diaper included in the discharge from the 10th floor (see table 3)).

° Dash-marks indicate either no data were taken, or that the data taken were irrelevant to the particular tabulation. Trapseal measurements were not obtained at floors 1, 2, 4, and 6.

11
Trap seals were excessively depleted in two tests, to the extent that one or more seals were lost on the lower floors. These tests were 2AnET (a 141 gpm

total load with detergent, equivalent to about 487 fix- ture units®), and 2B (a 180 gpm total load with

clean water, equal to about 770 fu®), as shown in table 3. There was no suitable basis for predicting

whether the system would or should successfully with- stand these unusually large loads, so tests were made

to explore the matter. In evaluating the results of

tests 2AnKT and 2B. the following considerations are relevant

1. With loads of these magnitudes, many plumbing

codes require 5-in soil stacks with conventional venting.

2. The design hydraulic capacity of vented 4-in drainage stacks is approximately 144 gpm [14,15].

3. A rational plan for experimentation should in- clude a number of loads of different magnitudes ranging up to levels that result in failure. Tests 2AnET

and 2B provided this feature.

4. The purpose of introducing detergent into the

soil stack in these tests was to obtain some data on

the general phenomena of detergent action in DWV

systems. Actually, only bathroom fixtures were planned

for the stacks in the project under consideration. As

indicated in (6) below, existing criteria do not provide for estimating relative capacities of conventional versus single-stack systems with detergent loads.

5. Because conventional systems have not generally

been tested in the manner described herein, it does

not seem purposeful to speculate on the relative per- formance of conventional versus System X at load

levels approaching and exceeding the generally ac- cepted design loads for conventional systems.

6. The generally accepted criteria for sizing conventional soil and waste stacks recommended by

Hunter [16,17,18] and by Dawson and Kalinske

[19, 20] and further described by Wyly and Eaton

[15] were developed before synthetic detergents were

in general use. For this reason, estimates of relative maximum carrying capacities of single-stack and

conventional vented systems with detergents seem to be largely conjectural in the absence of suitable research on this matter. Table 8 shows the ratio between trap-seal reductions

in the WC trap and the lavatory P-trap as determined

at two or three different floors for each of several

different loads. These data show that trap-seal reduction for the WC trap averaged only 40 percent as much as for the P-trap.

A number of tests were made to explore the effects of sanitary napkins, paper diapers, and detergents on trap-seal retention (tables 8A and 8B). Such

additives evidently caused scatter in the data. More

testing would have provided an improved statistical basis for conclusions on these matters. In the tests made, the relative trap-seal retention with diapers

" Fixture-unit values were obtained from "Hunter's Curve" for drainage systems, following the method outlined in certain NBS

publications [15, 16, 17). The term fixture-unit, abbreviated herein

as fu, is a measure of the probable discharge into the drainage

system by various types of plumbing fixtures. The fixture-unit value

for a particular fixture depends on its volume rate of drainage

discharge, on the time duration of a single drainage operation, and

on the average time between successive operations during peak-use

periods

was not reduced by more than 0.07 below the cor- responding values obtained with clean water. Similarly, the corresponding maximum reduction for sanitary

napkins and detergents were 0.04 and 0.11, re- spectively.

Table 8. Ratio of average seal reduction in WC trap to that

in P trap with various loads

Load' Floor No. runs for each trap WC/P

RatioAH,

lA ' 75

3

3 4/4

2/3

6.28

.50

IB * 75

3

4/4

4/4

".32 .39

IB 75

3

4/4

4/4

'.35 .37

1B*N 75

3

4/4

3/4

".24 .39

IC 7

5

3 4/4

3/3

.29

.42

5 75

3

1/1

1/1 1/1

.20

!50

.43

^DET 75

3

3/3

3/3

3/3

.45

.66

.63

6 7

5

3

2/2

2/2

2/2

.28 .54

.43 Avg. 0.40

^ See table 3 for description of loads. 'Based on average values from indicated numbers of identical runs. "AH" is trap-seal reduction produced by the indi- cated load. Identical units used for Affwc and Af/p in computing the ratio.

^ Dash-marks indicate either no data were taken, or that

the data taken were irrelevant to the particular tabulation. Trap-seal measurements were not obtained at floors 1, 2, 4, and 6. at i

• 'Subscripts are abbreviations of D for diaper, N tor sanitary napkin, and DET for detergent.

Observations were also made for the effects of sanitary napkins, paper diapers, and detergents on

pneumatic pressure excursions in the soil and waste

branches. The data for sanitary napkins and paper

diapers are rather erratic; their true effects on

pressures are not altogether clear, partly because of an insufficient number of replicate measurements. The detergent data show considerable increase in momentary pneumatic pressure excursions in the majority of the tests. The data in tables 7 and 7A show an average

trap-seal retention of more than l^/o in for every test condition. With the heavier loads, considerable scatter

in the data was observed from run to run, especially

with detergents and paper diapers.

12
Table 8A. Effects on trap-seal retention ' caused by additives to simultaneous hydraulic loads

Additive Floor Relative trap-seal retention ('-

AW \

H 1

<

Clean water" Additive

1 Change

Paper diaper

(loads IB * and IB

7

5

3

0.87

.68

.oZ

0.81

.61 .69

—0.06 - .07 + .07 Sanitary napkin

(loads IB * and 1B*n) '

7

53

.87

.68

.62

.88

.64

.72 + .01 — .U4 + .10 Detergent

(loads 5 and

7

5

3

.86

.71 .67

.87 .60

.68 + .01 - .11 + .01

' Data from table 7.

" Loads described in table 'A positive change 1 + ) retention with the additive.

3.indicates greater relative retention with the additive, and a ne;»ative change ( — ) indicates less

* "Af/" is trap-seal reduction; "W is the full trap-seal depth.

Table 8B. Effects on trap-seal retention^ caused by paper diapers with time- sequence variations of load IB'

Floor Time delay

(sec) Relative trap-seal retention

Clean water Jiaper Change

7 1.5 0.97 0.98 +0.01

3.0 .87 .85 - .02

4.5 .90 91 + .01

5 1.5 .98 .99 + .01 3.0 .88 .83 - .05

-1.5 .93 .89 - .04

3 1 5 .98 .99 + .01 3.0 .90 .85 - .05 4.5 .91 .90 - .01

' Data from table 7A.

^ Loads described in table 3. "A positive change (-f) indicates greater relative retention with the diaper load; a negative change ( —) indicates less relative retention with the diaper load.

* "AH" is trap-seal reduction; "H" is the full trap-seal depth.

4.1.1. Relation between Trap-Seal Reduction and Pneumatic Pressure The data in tables 9A and 9B have been presented

in a form that reveals the consistency of the relation- ship between trap-seal reductions and the pneumatic

pressure excursions causing such reductions. Although

the data do not possess strong statistical attributes, it is apparent that the trap-seal reductions were in most

instances less than the corresponding maximum negative pressure excursions, particularlv for the WC traps. The data suggest that in cases involving relatively

large pulsating pressure changes, the rocking of the water in the trap seals might have been the cause of greater trap-seal reductions than would be expected

from the assumption of steady-state pressure differentials. As discussed in the appendix in paragraph 7.1. the pressure measurements made in the 10-storv tower and

reported herein were made using the batterv of basement manometers. Apparently the correlation between dynamic pressures measured by four differ- ent methods was poor; so for the purposes of analvsis

it was decided to utilize the measurements taken on

the basement manometer battery, in keeping with the usual practice at the LdSB.

Generally, the ratio between pressure excursion and

trap-seal reduction was more consistent for the WC

trap than the smaller P-trap, and trap-seal reduction

in relation to pressure excursion was relatively less for the WC trap than the P-trap. Probably this was

because of the greater mass of water in the watercloset trap, a condition which tends to give greater

stabilitv and resistance to adverse effects from transient phenomena such as rapidly fluctuating pneumatic pressures. Averaging values in table 9\ (for those loads not involving the discharge of bathtubs)

shows that trap-seal reduction in the P-traps was about

78 percent of the pressure excursion for both positive

and negative pressures. Average trap-seal reduction

for the water-closet was about 29 percent of the average of the peak negative pressure values and

3.5 percent of the corresponding average of positive pressure values. These compare with a similarly

derived ratio of about 67 percent reported by Lilly1.3
Table 9A. Ratio of average^ trap-seal reduction to average'^ pneumatic-pressure excursion for loads not involving bathtubs. ^H 2 Ratio AP

Lofld r loor P-trap WC trap

+

— +

lA 8 U.D (3 A /I Au.4y3 7 .47, .473 5 I.OI3 .793 3 0.853 1.423 lA 8

7 .74 .47

1;0 1.32 1.97 0.37 0".55 3 0.74 0.87 .373 .432

IB 8

3 7 0.48 0'.32 5 .53 .99 3

IB1.61ICIV

* 8 — — 7

O.O83 c0 .3O3 .433 3 .3I3 .543

IBi.edD

' 8 — — 7 OIO3 0~053 0 .343 .193 3 .2I3 .293

IBj.odcw 8 — — 7 0.143 6.12,

c. 0 .433 .473 3 .273 .333

IBs OdD 8 — —

7

0"'.033 O'.oia c0 .663 .393 3 .4«3 .253

IB4 6Jcw 8 — — 7 0J43 0~.073

c: 0 .3I3 .443 3 .3O3 .293

IBi.edD 8 — 7 0".i33 o'oi,

1; 0 .353 1.173 3 .3O3 O.3O3

IB * 8 0.50 0.67 7 .88 .46 0 1.25 1.57 o'io 0.50 3 0.82 0.74 .32 .29

8 0.48 0.95 7 .88 .54 — III

.96 1.85 0.23 0.44 3 .79 0.67 .3I3 .263

8 0.78 0.89 7 1.33 .36 — __. 0 0.94 .23 0.33 0.79 3 .66 .12 .ZD 07

IC 8 0.42 0.21

7 .51 .22 5 1.05 1.21 3 0.89 0.92

Av., all -0.78 +0.79 -0.29 0.35 values ^Average of 4 identical runs, except where otherwise indicated. Subscripts on listed values indicate number of runs when

less than four.

' AP is pressure excursion in trap arm or horizontal branch produced by indicated load (see table 3), and A// is the reduction in trap-seal depth, both expressed in identical units of water column.

' Dash-marks indicate no data were taken, or that the data taken were irrelevant to the particular tabulation. Trap-seal meas- urements were not obtained at floors 1, 2, 4, and 6.

* Subscripts are abbreviations of cw for clear water, d for delay in seconds, D for diaper, and N for sanitary napkin.

14
Table 9B. Ratio of average^ trap-seal reduction to average'' pneumatic-pressure excursion for loads involving bathtubs.

Load Floor

Ratio AH

AP

P-Trap WC Trap

+ — +

o

Qo

3 7 U.OUi U.iUi co l.OOl z.UUi .0 /

3 2.30i 2.3O1 1 on. 1 on.

^DET 8

7 "973 0.83, OAS, 0'37, 5 1.293 2.803 .85, 1.83, 3 I.OO3 1.083 .63, 0.68,

6 8 O.4O2 0.242 7 1.20 3.6O2 o"332 LOO2

5 I.4O2 2.24= .75= I.2O2 3 1.092 I.4O2 .472 .6O2 Av., all values —1.24 +1.70 -0.60 +0.86

^ Subscripts on listed values indicate number of runs.

' AP is pressure excursion in trap arm or horizontal branch produced by indicated load (see table 3) and AH is the reduction

in trap-seal depth, both expressed in identical units of v^ater column.

' Dash-marks indicate either no data were taken, or that the data taken were irrelevant to the particular tabulation. Trap-seal measurements were not obtained at floors 1, 2, 4, and 6.

white and Wise [21] for British washdown water

closets, the traps of which hold less water than do

those of the American WC's used in these tests. The data for tests involving bathtubs (see table 9B) yielded noticeably different ratios. For three

tests (5, Sdet, and 6) average trap-seal reduction in the P-trap was 1.24 times the average value of peak

negative excursions and 1.70 times that for the corresponding average of positive pressure values. Average trap-seal reduction in the WC trap was 0.60

times the average value of the peak negative pressure excursions and 0.86 times the corresponding average

of positive pressure values.

4.1.2. Effects of Load Distribution

Tests with multi-fixture simultaneous loads in which

two or more of the vertical distributions of load ele- ments were tried, showed that in most cases pneumatic

pressure excursions were reduced when the vertical spacing between the elements was increased. This

agrees with indications from European studies [21,

22, 23].

Table 9C shows results of tests to determine pres- sure excursions using Load IB with three different

These results suggest that water closet traps of the type used in the tests resist trap-seal reduction more

successfully than small-bore P-traps. The results also suggest that if trap-seal retention is taken as the cri- terion of hydraulic performance, hydraulic loads that are of short duration or of transient nature (such

as the composite discharges from WC's and LAV's)

tend to produce less trap-seal reduction in idle traps

for a given magnitude of pressure excursion than do

long-duration, near-steady-rate composite loads such

as bathtub discharges.

by Elevation and Time Sequence

degrees of time delay between the discharge of the 10th floor WC and the 8th floor WC (see table 3).

No pattern of relationship is evident from the limited

number of measurements made.

In most of the comparisons in table 9C the delayedsequence diaper loads yielded greater pressure excursions than did the comparable delayed-sequence clean- water loads.

4.1.3. Unvented Offsets

Concerning the use of unvented offsets in the

stack, some writers have suggested that an advantage

of System X design stems from the falling water being

slowed down by the double-offset-like geometry of

this System's aerator" fitting. A double-offset fitting with suitable radius of

See fipure 2 for illustration. In essence, the flow in the stack is

first deflected laterally and then returned to the original line of flow by means of a single fitting or an assemblage of two or more fittings

in series. " The aerator fitting is sometimes called a mixer fitting.

curvature probably can simulate such slowing effect on the water velocity by a normal System X aerator

fitting, and such fittings used in place of idle aerator

fittings would provide a cost reduction in those branch

intervals where no soil branches need be provided

for.Double offsets were not planned for the project

in Fairfax County, but because they might be relevant

in other installations, the test stack was provided

15
Table 9C. Effect on average of peak pneumatic pressure excursions resulting from variation of time sequence for load IB^ in 10- story stack tests

Floor

Ratio P

Test load

'

IB, 1B:,.,„„.„ IB. IB, IB, .SdD + + - + + - + - + - +

9 l".oo" 1.00 1.41 0.73 1.41 2. CO 1.41 1.20 1.29 0.87 1.29 1.06 1.41 2.46

7 1,00 1.00 0.5.3 1.10 0.60 1.09 0.67 .50 1.80 .82 0.67 0.91 0.60 1.22

6 ].00 1.00 .55 1.03 .70 1..58 .60 .84 .90 .98 .95 .53 2.70 1.33

S 1.00 1.00 .72 0.92 .72 2.40 .46 .76 .44 1.33 .54 .68 0.72 0.40

4 1.00 1.00 .77 .65 1.12 1.59 .84 1.51 .81 1.29 .71 1.21 1.11 1.70

3 1.00 1.00 .65 .40 .94 0.66 .59 .46 .50 .94 .73 0.57 0.77 0.74

2 1.00 1.00 1.00 .94 .76 1.28 .72 .82 68 1.09 .68 1.24 .72 1.26

' Loads described in table 3. 'Average of 3 identical runs, except where otherwise noted.

is average of peak pressure excursions in branch produced by two-floor load with a time delay between upper and

lower element; Ps is average of peak pressure excursion for the case of a simultaneous discharge, i.e., delay=0, employing

clean water. 'Symbol "cw" stands for clean water; "D" stands for diaper. For example, designation IB3 odD represents load IB with

a 3.0 sec time delay, with a paper diaper included in the discharge from the 10th floor (see table 3). Symbol "s" stands

for simultaneous, and "d" stands for time delay. For the purpose of this table, the data for Load IBscw have been shown with a value of 1.00. Therefore, the data for time delay loads show effects relative to the simultaneous loads.

with offsets at floors 2, 4, and 6, as indicated in figure

2. Owing to the urgency imposed by a tight schedule

for the test program and to delays in arrival of the prescribed American fittings to be used for the double

offsets, European fittings were substituted. Later comparison of the standards for the respective fittings revealed that the European radius was less than the American one (approximately 75 mm versus 95 mm)

.

It is generally understood that the radius and shape

of any fitting that serves to deflect the water falling

down the stack of a single-stack system must be

carefully selected to avoid the generation of adverse

pressure differentials. Too small a radius may cause

plug-action at the offset, accompanied by excessive

pneumatic pressure excursions. Some European designers of single-stack systems have recommended omission of all unvented bends in the stack above the bottom of the lowest branch interval. The measurements obtained on the stack in the

test tower showed somewhat greater pressure excursions and trap-seal reductions at and below the double-offset fittings than might have been expected

from a consideration of similar previous European

data obtained without offsets. The European investigators feel that performance

of the test system in the lower part of the stack would have been better had the longer radius American offset fittings been used as planned. Additional

tests could provide the data needed to fully evaluate

this characteristic, but the program described herein

did not permit further tests. It is not considered

essential that such tests be made in evaluating the proposed designs.

4.2. Tests on Sinjjle-Interval Systems

4.2.1. Plan-A System

Table 10 shows relative trap-seal retention for

several loads applied to the Plan-A system. Average

relative retention for multiple single runs was not

less than 0.91, minimum single-run retention was

0.86, and the one (2-run) cumulative seal retention

test made showed a relative retention of 0.86. Table 11 shows that maximum water depths in the

3-in horizontal soil and waste branch were never as great as the branch diameter. The full-pipe condition was approached only with the unlikely load, designated 3n+ni.;T, created by a special ball-shape preforming of the diaper before flushing. The less-thanfull pipe condition and the straight-inlet geometry

of the 3-in combination soil-and-waste branch con- nection to the aerator (mixer) fitting evidently account

for the fact that pneumatic pressures in the idle 2-in horizontal drains connected to the 3-in branch were

not significantly different from the pressures within

the body of the aerator fitting. Evidently, in the de- sign tested the straight-inlet geometry of the 2-in waste branch fitting made possible the venting of the idle waste fixture traps by permitting air to move over the top of the water flowing in the 3-in combination soil- and waste-branch.

16
Table 10. Relative trap-seal retention in lavatory trap in tests on single-interval system, plan A '

Test load number

22C

Sd+det

Relative P

trap-seal retention

r\. Vci dgc if\'1 1 n 1 m1 1 lYi 1. 1 11 X 111 UIll

1.00^ 1.00,

0.993 0.96.1

.862 .862=

I.OO4 1.00,

0.98. 0.96.

.9I4 .864

' See figure 5 and table 4.

" "AW" is trap-seal reduction, and "H" is the full trapseal depth. Subscripts on values indicate the numbers of successive test runs made.

' Identical values obtained in each run of 2-run cumulative

series.

* Subscripts are abbreviations of D for diaper and DET

for detergent.

4.2.2. Plan-B System

As shown in table 12, test load 7 with layout 1 produced a few trap-seal reductions greater than or- dinarily considered acceptable. Improvement was evi- dent with layout 2. which involved enlarging the common horizontal waste branch from 2-in to 3-in diameter (branch no. 1, fig. 6) and replacement of the double elbow with a double long-turn T-Y fitting

(fitting no. 1, figure 6) . With layout 3, no reductions

of any significance occurred. Layout 3 differed from

layout 2 in the replacement of a short^urn bath-waste

fitting with a long-turn fitting (fitting no. 3, fig. 6).

Table 13 shows that with layout 3 trap seals were

reduced only slightly below full-seal level with various

loads. The data do not show any serious decrease in trap-seal retention due to bubble-bath (type 3 de- tergent) additive.

T.4BLE 11 Estimated maximum water depths in 3-in soil branch of single-interval system, plan A

'

Test load number

Estimated maximum value for ratio of water depth to branch diameter, H 'D

Average Maximum

1

0.64'

2 .83 .8,

2C .9= .92

3

= .84 .94

.9, .94

3 D+DET .94 1.0,

' See figure 5 and table 4. Depths estimated visually by

observation through transparent plastic window in top of

soil branch (point 1, figure 5). ''Based on 4 runs with decreasing head (run-to-run) in vessel simulating bathtub; i.e., head decreased because water was

let out for a short period of time in each run and not refilled between runs. Max value of H/D—Q.9 for 1st run and min

va]ue=0.8 4th run. Subscripts indicate the number of replicate runs.

* Subscripts are abbreviations of D for diaper and DET

for detergent.

Observations through a transparent window (point

5, figure 6), when one or both WC's were flushed,

showed some cross-flow into the common horizontal waste branch. This effect was greater with the flushing

of paper diaper loads than with clean-water loads. Visual observation suggested that a downward exten- sion of the baffle in the System X mixer fitting by

an estimated one inch should prevent the cross flow. Experimentation with a modified baffle could not be carried out in the time available for the tests. It

is understood that the final design of the fittings would

incorporate a lowered baffle.

4.3. Site Visits, Interviews, and

Literature Review

From site visits, interviews with authorities, and

review of literature, a number of significant findings were developed. At Le Lignon housing development in Geneva, 4-in System X stacks have been installed, each serving as many as 30 bathrooms and 30 kitchen sinks. These

systems had been used in Le Lignon for more than 5 years at the time of the site visit. In the National Plumbing Code [14] a bathroom

"group" with bathtub, tank-type WC, and lavatory

is rated at 6 fu, a bidet is rated at 4 fu, and a kitchen sink without food-waste grinder is rated 2 fu. Computations using such ratings would yield a con- nected load of 360 fu on the Le Lignon stacks which

is equivalent to 60 bathrooms of the variety being

considered for installation in the project in Fairfax

County, Virginia, assuming that the important hydraulic properties of such fixtures and the patterns

of fixture use are similar in their net effects in Switzerland and Fairfax County, Virginia.

A YMCA-type, 20-story building with 3 WC's per

floor was said to have functioned satisfactorily with

a 4-in System X. It is assumed that in addition there were 2 lavatories and 2 showers on each floor, the

total fixture unit load would be 360 fu, based on the

fixture-unit ratings of the National Plumbing Code.

Again, this would approximate the load produced by

60 American-type bathrooms, assuming like hydraulic

fixture properties and like use patterns.

Many Swiss System X installations are said to involve 40 bathrooms (20 stories of back-to-back

bathrooms) on a 4-in stack. Such a design for the Tscharnergut apartments in Bern was reported as receiving in addition to the bathroom load, the discharge from 40 kitchen sinks without food-waste

grinders. This loading yields a total of 320 fixture

units, estimated equivalent to 53 standard American

bathrooms without kitchen load figured as above. It was learned that in many installations storm water from the roof is also drained into the sanitary stacks. Swiss engineers thought it unlikely that peak rainwater

loads and design peak sanitary loads would occur

simultaneously.

A System X installation was visited in Montreaux

that served 27 stories of back-to-back bathrooms with an estimated fixture-unit group rating of 11 per

" Equivalency of Swiss and American loading effects is by no means certain, in the absence of detailed research on load patterns under American conditions. " Installations of System X in this project date from 1961.

17
Table 12. Effect on relative trap-seal retention oj changing piping arrangement for single-interval system. Plan B test load 7

'

Layout

number

Number of runs

Relative trap-seal retention

• ('

£Ji \ ~ir I

s

WCi WC, Li U B. B.

Av. Min Ay. Min Av. Min Av. Min Av. Min. Av. Min.

1 3 1.00 1.00 1.00 1.00 0.81 0.71 0.% 0.94 0.75 0.57 0.45 —0.10

2 3 1.00 1.00 1.00 1.00 .93 .91 .96 .96 .93 .86 .72 0.17

3 2 1.00 1.00 1.00 1.00 1.00' 1.00' .99" .99' 1.00 1.00 1.00 1.00

' See figure 6 and tables 5 and 6.

" "AW" is trap-seal reduction and "//" is the full trap-seal depth. Also abbreviations are WC for water closet, L for Lavatory and B for bathtub. 'Corresponding value of 0.% obtained next day with different operators (2 runs). 'Corresponding value of 0.93 obtained next day with different operators (2 runs). 'Corresponding value of 0.93 obtained next day with different operators (2 runs).

Table 13. Relative trap-seal retention in tests on single-interval system, layout 3 plan B

'

Test load no. No. Tuns

Relative trap-seal retention, (- AH \ H 1 WCi WC-" U B, B-' Av. Min. Av. Min. Av. Min. Av. Min. Av. Min. Av. Min.

3 4

3 0.96 0.86 1.00 1.00 1.00 1.00

O 0 •^DET 1 .90' .90 0.99' 0.99' 0.99' 0.99

4 2 1.00 1.00 .94 .93 1.00 1.00

^DUT 2 1.00 1.00 .94 .93 1.00 1.00

5 4 1.00 1.00

5d 2 0.99 0.99

6 4 1.00 1.00

7

11

2

3

0.96 0.93 0.93

.94

0.93

.93 0.93 0.93 ^DET 3 .84 .79 .93 .93

' See figure 6 and table 5.

' "AH" is trap-seal reduction, and "H" is the full trap-seal depth.

' Dash marks indicate in general that no measurement of trap seal was made. 'Cumulative relative retention in 4-run series:=0.86.

' Cumulative relative retention in 4-run series:=0.97. '.Subscripts are abbreviations of D for diapter and DET for detergent.

bathroom or a total of 594 fixture units, figured

as described above. This installation utilized 5-in

stacks. Under most American codes, 5-in stacks would also have been required for such a fixture- unit load and would have required conventional

venting.

With respect to the elements of the Swiss design

that guard against self-siphonage of active fixtures,

and against the induced siphonage of idle fixtures (as might result from discharge of other fixtures connected to the same horizontal branch as the idle fixtures), the principal basis for the design rules appears to be the research of Dr. Schellenberg, one

of the leading Swiss authorities in plumbing engineering. This research was conducted at the laboratories

of the City of Zurich, as well as at the LdSB. The

"Two lavatories, 1 bidet, 1 WC (tank type), and 1 bathtub.

rules were published in 1966 [24], The main ap- proach recommended for avoiding siphonage of traps

in a given branch interval (as caused by the discharge

of one or more fixtures within that interval) was to

size the various elements of the branch-piping system

so that full-pipe flow would not occur at any section where such "plug formation" might result in adverse

pressure differentials. In accomplishing this, fittings

used to change direction should be selected that would

not cause substantial interference with the normal

flow pattern nor unduly restrict the air space above

the water in a horizontal drain. In this way, it is possible to maintain effectively an air space above the water in the horizontal branches, and to provide "wet

venting" capability in the short vertical waste pipes

that in the System X design are connected to the downstream outlet of off-the-floor fixture traps. Thus,

the design seeks to control self-siphonage and to

18
equalize pneumatic pressures between the atmosphere,

the trap arms, and the mixer (aerator) fitting by ad- mitting sufficient air relief through incompletely filled drainage piping.

Discussions with a local plumbing authority in Winterthur, several mechanical engineers in Zurich

and Geneva, a plumbing contractor in Winterthur,

and research and code experts in Zurich and Bern

in 1967 and 1969 revealed no problems with fouling

or corrosion that they considered attributable to the omission of secondary ventilation. Further comment

on this will be found in the appendix.

5. Summary

The information reviewed and the new test data

obtained in this study provide a basis for the following

conclusions:

a. The study showed that, within the scope of the

investigation as carried out, it is reasonable to expect

satisfactory hydraulic and pneumatic performance of

the proposed single-stack installations in Fairfax County, as determined by the ability of the system tested

to maintain more than in of water seals in the

traps, with test loads as estimated by an application

of probability theory greater than those expected in the proposed application. It is important that generally accepted quality of design, installation, and

inspection be maintained, for both conventional and

single-stack systems, to assure satisfactory operation.

b. A number of these systems installed in Swiss

apartment buildings have been identified that serve

loads believed equal to or greater than those expected

for the proposed project in Fairfax County.

c. Tests in tall Swiss apartment buildings with

manually-produced hydraulic discharges greater than

the peak discharge rates predicted from Hunter's curve for the systems proposed for the project in Fairfax County have yielded measurements indicating

satisfactory pneumatic conditions.^'' Long-term monitoring of the pressures in the same systems with

natural loadings after occupancy of the buildings

showed smaller pneumatic pressure excursions than

exhibited in the manual tests. d. Laboratory measurements with various loads on a 10-story test system closely simulating the de- sign proposed for the project in Fairfax County

showed that average trap seal retention was not less than about 56 percent of maximum seal depth, and

that no waste water or air was forced back through

the traps. This was true even with simulated bath- room loads giving discharge rates greater than pre- dicted from 50 standard American bathrooms according to Hunter's peak-discharge curve.

e. Protection against self-siphonage of active fix- ture traps and against induced siphonage of idle traps

(by the discharge of fixtures in the same branch

15 NBS BMS 65, Methods of Estimatins Loads in Plumbing

Systems.

16 Pressures within approximately ± 1-in water column, referenced

to atmospheric pressure " It is understood that in Europe these rules are customarily

applied by qualified design engineers familiar with the System X

system, and that the same principles are to be applied in designing Americn installations. SSIV is Schweizerischer Spenglermeister-undInstallateur-Verbandes, Auf der Mauer 11, 8023 Zuricli, Switzerland.

interval as the idle traps) appears possible by fol- lowing design rules patterned after the 1966 recom- mendations of the SSIV [24]". The substance of these recommendations should be incorporated in the System X design.

f. A 90-degree horizontal-to-horizontal change in drain direction should be accomplished gradually,

such as through the use of a long-turn T-Y fitting in preference to a short-turn fitting, or through the use

of a 90° long-radius elbow or two 45° long-radius

elbows in series.

g. The data suggest that where two horizontal waste lines from opposite directions, one or both of which serve two or more fixture units, are joined

to a common horizontal branch at the same axial

point, the common branch should be 2^/2 or 3-in diameter.

h. The tests with paper diapers showed that with some hydraulic loads the diapers caused an increase

in pneumatic pressure excursions and trap-seal re- ductions. The effect of detergents was less well- defined, but the indications are that this too may

increase pneumatic pressure excursions and trap-seal

reductions in some instances. The tests with sanitary

napkins did not appear to show a significant effect from their use. Average trap-seal retention was (1)

at least 56 percent of the original trap-seal depths for

a range of clean-water loads up through 145 gpm

(or 515 fixture units from Hunter's curve) and

(2) at least 61 percent for paper diaper loads up

through 118 gpm (350 fixture units)

i. The data showed that the WC traps were much

less subject to seal reduction than were the P-traps,

and suggested that greater loads can be allowed for

a given trap-seal reduction than for a pneumaticpressure excursion of the same magnitude. Therefore,

in the further refinement of evaluative techniques for sanitary DWV systems the primary criterion should

be trap-seal retention rather than pneumatic pressure

excursion.

j. The vertical distribution of the elements of a compound hydraulic load affects pressure excursion

and trap-seal retention. The worst case appears to be

the introduction of the load elements as close together

as possible, near the top of the stack, and this tends

to be the practice in testing because of the limited height of the available laboratory test apparatuses.

However, in natural loading the individual elements

of a compound load probably will tend to be dis- tributed along the length of the stack rather than in a close-together-grouping near the top. Since the

test loads were introduced close to the top of the stack, the corresponding allowable natural, fixture-unit loads

inferred by the method described herein should be on the safe side. This should tend to compensate for any adverse influence from unequal hydraulic load

patterns in Swiss and American usage.

k. Although the guides given herein for selecting

For comparison, the presently proposed maximum fixture-unit load iier stack in the Fairfax County project is 312. which should produce a jieak discharge of approximately 112 gpm according to Hunter's curve. The effects produced by this load were apparently intensified to some degree because of the diapers. A compound hydraulic load is comprised of two or more indi- vidual elements of discharge, introduced with some degree of concurrence.

19
test loads are useful, they do not assure that the field performance will agree exactly with the test performance. European data show that pneumatic pressure

excursions, monitored instrumentally with natural

service loads, have been smaller than investigators

had predicted from tests [21,23,25]. In order to obtain closer agreement between test results and field performance, and to bring about desirable refine- ments in American evaluative technique, it will be

necessary to make comprehensive measurements in actual buildings with natural loads to better define

load patterns by time, magnitude, frequency, and

vertical distribution. Further comment on this will be found in the appendix.

Considerable research and development work has

been carried out to introduce System X into the United States, by plumbing engineers and its proponents in connection with design of systems to suit American buildings. However, much remains to be

done in developing realistic guide criteria for the design and evaluation of a wide range of systems that might employ some version of the single-stack principle, and yet might differ from the System X in

significant ways. It is important to identify and

define the controlling parameters and to investigate the performance characteristics over a range of repre- sentative conditions. This would permit the establish- ment of suitable test procedures and technical criteria for determining the design and acceptability of any

type of single-stack drainage system, irrespective of manufacturer, architect, or plumbing designer.

The authors acknowledge important contributions

made by the following persons:

Morris Shapiro and Norman Schrank, of General

Engineering Associates, whose design of the single- stack plumbing system for a high-rise building in Fairfax County, Virginia provided the opportunity

for this study.

W. Stuart Lyman and D. 0. Herrick, of Copper

Development Association, Inc., who arranged for the use of the laboratory test facility in Switzerland. Dr. O.H.C. Messner, Randolf Hanslin, Fritz Sommer, Thomas Pfau, and Hans Kopp were re- sponsible for conducting the laboratory testing in Switzerland.

6. References

[1] Guide Criteria for the Design and Evaluation of Operation BREAKTHROUGH Housing Systems—A Preliminary Report, NBS Report 10,200, Nat. Bur. Stand., 1970).

[2] Herrick, Dee 0., Copper Sovent Plumbing System, Refresher Course, 63rd Annl. Meeting, Amer. Soc. of Sanitary Engineering, September 29, 1969.

[3] Voegeli, Henry E., Drainage without vent stacks. Air

Conditioning, Heating and Ventilating (August 1963).

[4] Wise, A.F.E., Britain's single-stack drainage systems,

ibid., (April 1967).

[5] Nielsen, Louis S., European single-stack drainage sys- tems, Plumbing-Heating-Cooling Business, (Oct., Nov., and Dec. 1969 and Jan. 1970).

[6] Nielsen, Louis S., Performance test for single-stack sys- tem, Technical Forum, ibid., (April 1970).

[7] Dickerson, Donald F., Modem plumbing through the eyes of an engineered sovent system, First Biennial Engineered Plumbing Exposition of the Amer. Soc. of Plumbing Engineers, (Sept. 12-15, 1968).

[8] Dickerson, Donald F., How to design with sovent. Build- ing Systems Design, (Jan., Feb., and Mar., 1970)

.

[9] Copper Sovent Single-Stack Plumbing Systems Design

Handbook, Copper Development Assoc., Inc. (1970).

[10] Wise, A. F. E., and Croft, J., Investigation of single- stack drainage for multistory flats, J. R. San. Inst. 74, No. 9, page 160 (1954).

[11] Wise, A. F. E., Drainage pipework in dwellings: Hydraulic design and performance, DSIR, Bldg. Res. Station, London, England (1957).

[12] Sanitary pipework above ground. Code of Practice for, CP304—1968, British Standards Institution, London,

England.

[13] Griffiths, T. J., The hydraulic design of drainage pipework for domestic and public buildings, Proc. of the Public Works and Municipal Services Congress, London,

England (1962).

[14] American Standard National Plumbing Code, American

Society of Mechanical Engineers and American Public Health Assoc., ANSI A40.8-1955.

[15] Wyly, R. S., and Eaton, H. N., Capacities of stacks in sanitary drainage systems for buildings, Nat. Bur. Stand.

(U.S.), Monogr. 31, (1961).

[16] Hunter, R. B., Methods of estimating loads in plumbing

systems, NBS Building Materials and Structures Report

65 (1941).

[17] Plumbing Manual NBS Building Materials and Structures Report 66 (1941).

[18] Recommended Minimum Requirements for Plumbing,

Report of the Sub-Committee on Plumbing of the Build- ing Code Committee, U.S. Dept. of Commerce, Elimination of Waste Series, BH 13, (1932).

[19] Dawson, F. M., and Kalinske, A. A., Report on hydraulics and pneumatics of plumbing drainage systems, Bulletin No. 10, Studies in Engineering, University of Iowa

(1937).

[20] Dawson, F. M., and Kalinske, A. A., Report on hydraulics and pneumatics of the plumbing drainage system, Technical Bulletin No. 2, National Assoc. of Master Plumbers (1939).

[21] Lillywhite, M. S. T., and Wise, A. F. E., Toward a general method for the design of drainage systems in large buildings, CP27/69, Building Research Station, London, England (1969).

[22] Pfau, Thomas, unpublished test report to Copper De- velopment Assoc., Oderlin Co., Baden, Switzerland (No- vember 1966 and July 1967)

.

[23] Wise, A. F. E., Payne, R., and Griffiths, T. J., Sanitary

services for modern housing. Public Works and Municipal Services Congress, (1966).

[24] Basic Principles of Sewage Systems, Swiss Sewage Sys- tems Assoc., Zurich, Switzerland (1966).

[25] Pfau, Thomas, unpublished test report to CDA, Oderlin

Co., Baden, Switzerland (January and September 1966).

7. Appendix

7.1. Supplemental Details relating to experimental Apparatus, Test Systems, and Test

Procedures

The water closets used in the test program were

a current model siphon-jet flush-valve type made by

a prominent American manufacturer. Each WC was

equipped with a 1-in flushometer valve regulated to discharge approximately 4 gal (15 liters) during a period of 8-10 s, giving an average rate of discharge

of about 27 gpm (102 1pm ^i). The vertical interval between successive floors of the test system shown in figure 2 was about 8'-8"

(2.65 m). The stack was 4-in diameter copper DWV

tube.

' Ipni" is tlie abbreviation for "liters per minute."

20
System X fittings were fabricated from copper sheet

in the shops of the LdSB, following drawings provided

by an American fittings manufacturer. Two side entries were provided on each of the low-angle stack- branch confluence fittings. At the base of the stack, the deaerator fitting was connected to the building

drain by means of a 2-in vent, at a point downstream

of the 90° elbow. The building drain was 4-in dia

copper DWV tube. The discharges of bathtubs and lavatories were

simulated by the use of seven plastic tanks distributed on floors 10, 9, 8, and 7. Each tank was equipped

with a 11/4 in control valve for flow rate adjustment,

and a II/2 in quick-closing valve for starting and

stopping the flow by manual means. The tank-valve combinations were calibrated to give an average dis- charge rate of about 48 1pm (12 gpm was originally

intended) over a period of 102 s to simulate the discharge of a bathtub, and about 40 1pm (10 gpm

was originally intended) over a 7.5 s period to simulate the discharge of a lavatory. Pressure measurements were provided for by in- strumentation as follows:

1. Central battery of water manometers (estimated

25 mm, i.d.) in the basement below the test tower. These manometers were connected through runs of copper tube (estimated 15 mm, i.d.) and flexible rubber tube connectors to the horizontal branches on

each of the ten floors, and to the building drain.

2. A close-connected U-tube manometer (6 mm.,

i.d.) with a flexible coupling was installed at each of

the stations indicated in (1) above for comparison

with the basement manometers.

3. Magnetic-coupled gages were installed with close connections to trap arms of certain P-traps on floors

10, 9, 8, 7, and 5. 4. A continuous-recording pressure monitor de- signed at the LdSB was connected to one of the

idle branch outlets of the aerator fitting on the 7th

floor. In the discussions of pneumatic pressure measure- ments in the tests on the 10-story test tower (sections

4 and 5), the pressures referred to are those measured

by the battery of basement manometers, unless other- wise indicated. This method was chosen because of the apparently poor correlation of responses from

methods 1 through 4 above when measuring the same

dynamic pressure patterns, and because most of the research conducted earlier at the LdSB had been

carried out using the manometer battery.

Data obtained earlier at the LdSB have shown that under typical dynamic conditions in sanitary DWV

systems, different pressure-measuring instruments

yield different peak values, depending on the time

constants of the instruments as well as the dynamics

of the fluid motion within the instruments and gage

lines. Thus it is difficult to correlate dynamic pres- sure with trap-seal retention.

It is desdrable that test methods for the evaluation

of sanitary DWV systems be based on pressure meas- urements rather than trap-seal retention so as to simplify the measurement task; however, because the pressure measurements are unreliable indicators of

trap-seal retention, a substantial research need is

indicated for correlation of dynamic pressure ex- cursion with trap-seal retention. Trap-seal retention of the P-traps was measured by

piezometers connected through the cleanout openings.

The water closet trap-seal retention was measured by

graduated "dip-stick" scales. Additives to the water that were used in several

tests were paper diapers, sanitary napkins, and detergents. The diapers used were the large size of a popular brand, flushed through the WC's without

removal of the plastic membrane. For the test loads using diapers, only a single diaper was used with

each WC so identified. The sanitary napkins used were the large size of

a well-known American brand, flushed singly through

WC's where indicated, together with four 3-pc sections

of double-thickness toilet tissue of a popular American

brand.

The detergent loads were introduced by pouring

a water solution of about 200 ml into the bathtub

traps (see figure 3) for specified periods while water was being discharged through them. The concentrations used in the detergent loads were reduced to about one-half of the manufacturers recommendations to simulate some depletion of detergent strength

that usually occurs in a service condition before the

fluid is discharged into the drain. The detergent

loads were: Type 1 —74 cc of powdered detergent in water

solution introduced with a 12-gpm bathtub discharge

over a 1-min period—simulates use of automatic

clotheswashing machine (test no 5det on 10-story

stack)

Type 2—3.1 ml of liquid detergent in water solu- tion introduced with a 12-gpm bathtub discharge over

a 12-s period—simulates manual dishwashing in kitchen sink (test no. 2Adet on 10-story stack)

Type 3—32.5 ml of flake bubble-bath additive in water solution introduced with a 12-gpm bathtub

discharge over a 1.7-min period—simulates use of bubble-bath substance in bathtub (test no. 3d*det on single-interval system A; and tests no. 3det5 4nET and IIdet on single-interval system B)

7.2. Selection of Test Loads

Performance tests have been described for British

single-stack drainage systems [6, 12, 23] that |>ossibly

could have been applied directly in choosing the loads employed for the tests reported herein. However, in order to take account of some of the hydraulic

properties of American fixtures that may differ from

those of their British counterparts, it is believed the method used in deriving tables 2 and 3 is to be

preferred. The principal shortcomings of either ap- proach are (1) lack of adequate American data

establishing representative values of the average time

between successive operations of the fixtures, (2) lack of statistics on concurrence of peak-use periods

for different types of fixtures, and (3) lack of generally accepted rational method for selecting a

vertical distribution of a multielement hydraulic test load. A 50-bathroom connected load with 3 standard

fixtures per bathroom would require a "morning

21
peak" test load comprising 2WC + 2Lav, according

to the current British guide [12]. For comparison,

the use of table 1 yields a load of 3WC + ILav for —= 0.01 (load no. lA). For a 40-bathroom load,

T the British guide calls for 2WC + 2Lav while the use of table 1 yields 2WC + iLav, computed in ac- cordance with the procedure used for load lA in table 2. The British guide is shown in table A-1. Thus it can be seen that the magnitude of the loads

obtained from the use of the British CP 304 guide

table may be roughly comparable to those obtained

from the use of table 1, the difference being largely

in the use factors and hydraulic properties assumed

for the fixtures, and in the method of allowing for the unlikelihood of concurrence of peak loads in two or more groups of plumbing fixtures of different

types.

Table A-1. British guide^ for selecting numbers of fixtures

to be discharged in testing sanitary DWV systems for dwellings.

Number of fixtures to be discharged

simultaneously

Number of fixtures

of each kind on Two-gal. (9 liters)

Wash Kitchen

stack water closet Basin Sink

1-9 1 1 1

10-24 1 1 2

25-35 1 2 3

36-50 2 2 3 'From CP 304-1968 [12]. In using this guide, the British practice is to compute separately the number of each type

of fixture to be discharged, taking into account the time of day when peak usage for each fixture type may be expected.

"Approximately 2.4 American gallons.

Table 1 offers advantages in providing for choice of —T (level of overload risk) and for ^

T

(ratio of duration of fixture operation to average

time between successive uses). The table, together

with the explanation of its use, also provides for the

exercise of judgment in the application of data

relating to concurrence of peak periods of use for

different types of fixtures. For example, are kitchen

sinks in peak use at the same time of day as water

closets ? Are bathtubs in peak use at the same time

as kitchen sinks, etc.? Table lA should prove useful in selecting reasonable test loads for the evaluation of hydraulic inter- actions in systems or portions of systems installed within a single branch interval. The assumption of a larger value of for table lA than generally

assumed in the use of table 1 for the testing for

effects between branch intervals is not unreasonable,

because this takes account of (1) the inherent

likelihood that actual values of ^ will frequently

deviate substantially from average values, especially

in small systems, and (2) the consequences of an overload of one fixture beyond the design load can be

relatively more significant in a system comprising a small number of fixtures than in a large system.

Both tables 1 and lA, as well as the procedures

for their application, may need adjustment as new

research data on the hydraulics of plumbing fixtures and appliances, and on use patterns in service become

available. Standardization in this area is needed, both

for laboratory and field applications. The scope of such standardization should include procedures for

field tests utilizing steady flow or simulated short duration fixture flow that could be utilized on rough

plumbing before the work is closed in and fixtures

installed, as well as for tests with fixture loads that could be made later before occupancy.

7.3. Evaluation of Branch

Design Finally Selected

The branch designs finally selected for installation

in the project in Fairfax County should be compared

with the designs tested to establish whether the principal values of the test results have been realized insofar as possible in the final design.

7.4. Optimum Hydraulic

Properties of Fixtures

Trap-seal retention in idle traps apparently is greatest in traps with a large water seal. Therefore,

ll/2-in traps used with lavatories and 2-in traps with

bathtubs and kitchen sinks should be preferable to the smaller sizes often used, from the standpoint of trapseal retention. Similarly, trap-seal depths of at least 3-in should be preferable to 2-in. Trap-seal retention is also improved when the

fixtures have relatively low rates of discharge and

discharge relatively small volumes of water. Water

closets with volumes of less than 4 gal and peak

momentary discharge rates less than 35 gpm should

be specified if possi]>le.

7.5. Fouling and Corrosion in DWV Systems

Fouling and corrosion are complex pnenomena in any DWV system, and are not adequately understood

in conventional systems. No experimental or theoretical evaluation of these factors was attempted in the present study. A review of the literature on the system tested and interviews with several Swiss ex- perts showed no cause for concern. However, since

this question may deserve further study under American service conditions, it should be considered in any new research on single-stack systems. Follow-through

studies of maintenance history in single-stack installa- tions and comparable conventional installations could

provide relevant information. Laboratory experimentation with various configurations, branch-pipe sizes, drain slopes, discharge rates, waste materials, and

other factors could provide valuable data supplementing the field observations.

22
7.6. The Value of a Follow-throufjh Research Program

It is widely recognized that new studies are urgently

needed to update and expand the criteria that are used by designers and evaluators of plumbing sys- tems. The needs are particularly acute in reference

to the prediction of peak hydraulic loads and to the

correlation of test results with field performance.

This is essential if simulative testing of DWV systems

in the laboratory is to be standardized. The potential

for payoff from an adequate program of research is evident not only in relation to the evaluation of innovative systems, but also in relation to the problem

of selecting reasonable safety factors for pipe sizing

in conventional systems. Estimates of the national

savings that could be realized through an adequate

knowledge of peak loads on plumbing systems and a

general application of such knowledge in the construction of conventional systems alone have ranged

up to several hundred million dollars annually.

The results of this kind of research could be of great and lasting value in connection with the nation's continuing need for housing. In particular, the type

of information that could be provided for the first time would be most beneficial in improving criteria and test procedures for industrialized housing systems.

The technology of such research is now available; and the resulting information would be most beneficial in improving criteria and test procedures for industrialized housing systems as well as more conventional designs.

23

FORM NBS-114A (1-71) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBS BSS-41

2. Gov t Accession No.

3. Recipient's Accession Nc

4. TITLE AND SUBTITLE

PERFORMANCE OF A SINGLE- STACK DWV SYSTEM UTILIZING

LOW-ANGLE STACK-BRANCH CONFLUENCE AND BOTTOM SHUNT VENTING

5. Publication Date March 1972

6, Perfonning Organization Code

7. AUTHOR(S)

Robert S. Wyly and Grover C. Sherlin

8. Performing Organization

10. Project/Task/ Work Unit No. 4212135

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Same

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Among the more important criteria for hydraulic and pneumatic performance of sanitary

drain-waste-vent systems are (1) maintenance of water seals in fixture traps, (2) limitation of pneumatic pressures, (3) limitation of hydrostatic and hydrodynamic pressures,

and (4) limitation of cross-flow between horizontal branches or trap arms.

Recent tests of a single-stack drainage system proposed for a high-rise apartment

project in Fairfax County, Virginia have produced the following findings with respect

to these performance criteria:

(1) test loads (total discharge rates) ranging up to magnitudes greater than predicted

loads yielded reasonable average trap-seal retention;

(2) the use of trap-seal retention as a measure of performance appears to be more meaningful than the traditional pneumatic-pressure measure;

(3) fitting geometry and branch arrangement can be more critical in single-stack

systems than in conventional vented systems, and

(4) present procedures for selecting test loads, for making tests, and for reporting

and interpreting measured values need improvement and standardization.

17. KEY WORDS (Alphabetical order, separated by semicolons)

Criteria for plumbing; hydraulic test loads; performance of plumbing; single stack

plumbing.

18. AVAILABILITY STATEMENT

[x1 UNLIMITED.

I I FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

24

22, Price

35 cents

USCOVM-DC 66244-P71

Announcement of New Publications in

Building Science Series

Superintendent of Documents,

U.S. Government Printing Office,

Washington, D.C., 20402

Dear Sir:

Please add my name to the announcement list of new publications to be issued in the series: National Bureau of Standards Building Science

Series.

Name

Company .

Address —

City State Zip Code

(Notification key N-339)

tt U. S. GOVERNMENT PRmXING OFFICE : 1972 O - 453-168

NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards^ was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety.

The Bureau consists of the Institute for Basic Standards, the Institute for Materials

Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates

that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics—Electricity—Heat—Mechanics—Optical Physics—^Linac Radiation^—Nuclear Radiation-—Applied Radiation^—Quantum Electronics^

Electromagnetics^—Time and Frequency^—Laboratory Astrophysics^—Cryogenics^.

THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of

well-characterized materials needed by industry, commerce, educational institutions, and

Government; provides advisory and research services to other Government agencies;

and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor

Radiation—Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to pro- mote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes

and methods of test; and provides technical advice and services to Government agencies

upon request. The Institute also monitors NBS engineering standards activities and

provides liaison between NBS and national and international engineering standards

bodies. The Institute consists of the following divisions and offices: Engineering Standards Services—Weights and Measures—Invention and

Innovation—Product Evaluation Technology—Building Research—Electronic

Technology—Technical Analysis—Measurement Engineering—Office of Fire Programs.

THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts re- search and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition,

and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center

consists of the following offices and divisions: Information Processing Standards—Computer Information—Computer Services —Systems Development—Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination

and accessibility of scientific information generated within NBS and other agencies of

the Federal Government; promotes the development of the National Standard Reference

Data System and a system of information analysis centers dealing with the broader

aspects of the National Measurement System; provides appropriate services to ensure

that the NBS staff has optimum accessibility to the scientific information of the world,

and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and

Publications—Library—Office of International Relations.

^ Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

2 Part of the Center for Radiation Research,

s Located at Boulder, Colorado 80302.
U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington. D.C. 20234

OFFICIAL BUSINESS

POSTAGE AND FEES PAID

U.S. DEPARTMENT OF COMMERCE

Penalty for Private Use, $300