Patrick]. Rehling and NicholasJ. i3artilucci
A July 1989 amendment
to the New York State Plumbing Fixture Law of 1980
requires that all buildings constructed
or renovated after 1992 be provided
with plumbing
furtures that are “water-effkient.”
This article describes a
fixture-use
procedure developed for estimating water consumption
in ofice
buildings and the utilization of the procedure to determine the reductions in
water usage possible through the installation of water-effkient
fixtures. Reductions of between 44 and 69 percent are estimated for water-efkient
plumbing
fixtures compared with older, conventional
fxtures.
Water conservation, long practiced in
arid regions of the United States, is receiving increased attention throughout
the country as a potential means of satisfying growing water demands. In an ef-
fort lo reduce the domestic component of
water consumption (water used for drinking or other sanitary purposes), several
states and the federal government have
enacted or are considering legislation
that revises current plumbing standards
to include toilets, urinals, lavatories,
shower heads. and other fixtures that are
water-efficient.’ One such piece of legislation, aJuly 1989 amendment to the New
York State Plumbing Fixture Law of
1980. requires that all buildings constructed or renovated after 1992 be provided with these water-efficient fixtures.’
In this article, a procedure is described
that can be used to estimate possible
water usage reductions in office buildings through the installation of watcr-efficient fixtures. Water usage data from
existing office buildings are correlated
with a theoretical estimating procedure,
which can then be used to project possible water savings. The office buildings
utilized in the analysis represent typical
office environments, The buildings contain minor nonoffkc amenities, such as
snack bars, small restaurants, and gift
shops. but are not mixed retail-commercial establishments with a high percentage of nonoffice utilization. Water usage
by minor nonoffice amenities in the buildings is factored into the analysis.
Water-efficient fixtures defined
For the purposes of this study, waterefftcient plumbing fixtures arc defined as
those fixtures that conform to the standards set forth in the July 1989 amendment to the New York State Plumbing
Code, whereas conventional fixtures are
those that were acceptable under plumbing codes at the time of the study. Table
1 compares unit water usage for fixtures
conforming to pre-1980 New York State
plumbing codes, the 1980 code, and the
July 1989 amendment requiring water-efficient fixtures.
As stated previously, this study was
limited to an evaluation of water usage in
office buildings;
consequently,
only
those plumbing fixtures typical of these
facilities, i.e., toilets. urinals, and lavatories, were considered. Water-efficient
showerheads and other tixtures would
result in little or no water savings in an
office environment.
Three areas assessed in investigation
The investigation consisted of three
parts: (1) determination of actual water
consumption in office buildings equipped
Copyright (C) 1992 American Water Works Association
.lOt!KNAI.
AWWA
with conventional
fixtures by using
meter records of facilities currently in
operation; (2) development of a theoretical estimating procedure, based on unit
volumes used by conventional fixtures,
to be correlated with field data; and (3)
incorporation of water-efficient
fixtures
into the theoretical estimating procedure
to project expected water savings with
their use compared
with plumbing
fixtures conforming to pre-1980 and 1980
plumbing standards.
Each office has its own character
Domestic water usage in an office
building depends on many factors, including building population, occupant
density, gender mix, and the type of
plumbing features provided. Development of the theoretical estimating procedure required many assumptions, which
may or may not be universally applicable.
local
codes
govern
occupant
density.
The maximum occupant density typically
permitted by local building codes is 200
sq ft per person.3 Although this value is
the code-mandated
maximum,
office
buildings in the study area generally operate at densities below this value, usually between 250 and 300 sq n/person.
Building occupancy
rates vary. Few office buildings operate at 100 percent occupancy. Occupancy rates depend on
many factors, including, for example, location and local economy. In addition,
building occupancy is reduced when vacation time, sick leave, holidays, and outof-office visits are included. The average
occupancy rate for office buildings in the
study area at the time of the meter record
evaluation was reported to range between 85 and 90 percent.*
Gender
sumption.
demographics
affect
water
con-
The gender mix in an office
environment can affect water consumption in the facility. Unlike their female
counterparts, male occupants have the
option of using urinals instead of toilets.
Urinals consume significantly less water
per flush than toilets.
Several tenant companies were surveyed in an attempt to determine an average gender breakdown for office buildings in the study area. The results of the
interviews are summarized in Table 2.
Gender demographics
varied widely
from tenant to tenant, with male populations ranging from 39 to 80 percent and
female populations ranging from 20 to 61
percent. The average gender mix of the
seven groups surveyed was 57 percent
men and 43 percent women. This is comparable to gender demographics
reported by other researchers for office
buildings (53 percent men, 47 percent
women) and mirrors the demographics
of the entire Long Island work force during the study period as reported by the
New York State Department of Labor (57
percent men, 43 percent women).4,” On
the basis of these various sources, an
OCTOBER
1992
TABLE
1
Comparison between conventional and water-efficient plumbing futures
as listed in the New York State Plumbing Code
~
*Revised
to 1.0 gal/flush
in 1987 amendment
TABLE
2
Summary ofgender demographics from telephone survey of ofice building tenants
Men
Tenant
Total
Employees
Type
Engineering
Cosmetics
company
headquarters
Investment
banking
Investment
management
Textile company
headquarters
Business
forms
Mixed services
Average
Restroom usage among men and women
about equal. Other researchers have esti-
mated typical restroom utilization in an
office building at approximately three
per day for men and women, with women
using toilets during every restroom visit
(three times per day) and men using the
toilet one time per day and the urinal two
times per day. Men and women were
found to utilize the lavatory during nearly
every restroom visit (three times per day
for men and women).“,”
Volumes
of fixture
units
number
percent
56
192
158
297
32
28
37
69
39
80
60
47
40
65
57
81
496
198
499
68
70
57
average gender mix of 55 percent men,
45 percent women was selected as typical
for office buildings in the study area.
determined.
Based on the approximate ages of the
office buildings in the study area, the
facilities were assumed to be outfitted
with plumbing fixtures conforming to
1980 New York State Plumbing Standards. These units are 3.5-gal/flush toilets, 1.5-gal/flush urinals, and 3.0-gpm
lavatories.
Other water consumption
must also be
factored in. In addition to water used by
plumbing fixtures, a number of miscellaneous water-consuming features require
consideration. Most modern office buildings include some nonoffice amenities
that affect water usage, including snack
bars, small restaurants, and gift shops. In
addition, occupants of the buildings
drink water, and water is used in service
sinks and for building maintenance. Factors such as leaking plumbing fixtures
and transient (nonoccupant) restroom
usage must also be included.
Metered water consumption
was examined
The first step in the analysis was to
determine water consumption in existing
W0lllell
number
25
304
40
203
36
42
20
percent
31
61
20
40
53
60
35
43
buildings
that utilize conventional
plumbing fixtures conforming
to the
1980 New York State plumbing code. Metering records over a three-year period,
obtained for 23 office complexes, were
analyzed in order to estimate average
water consumption. The data were categorized, assuming that water consumption in an office building falls into the
following basic groups:
l
irrigation water for maintenance of
landscaped areas;
l
cooling water for single-pass cooling or cooling water makeup;
l
domestic water for toilet facilities,
drinking fountains, and building maintenance; and
l
water used for accessory nonoffice
amenities such as snack bars, restaurants, and shops.
Water used for irrigation and cooling
can vary widely from building to building,
depending on the extent of landscaping
and the type of cooling equipment utilized. Domestic usage, however, is likely
to be similar in all office facilities and
directly proportional to building size and
population. It is this domestic component
that will be directly affected by water-efficient plumbing fixtures.
The meter record evaluation followed
the basic premise that because irrigation
and cooling water usage occur only during warmer months and domestic consumption takes place throughout
the
year, the domestic component can be estimated by averaging meter records for
fall-winter
months (October through
March) when irrigation and cooling are
not generally practiced. Table 3 summarizes the results of the evaluation. Water
consumption was standardized on a unit
basis by dividing average fall-winter and
Copyright (C) 1992 American Water Works Association
P.J. BEHLING
& N.J. BARTILUCCI
75
spring-summer
(April through September) water usage by the floor area of each
building and by 130 working days per
period (assuming a five-day work week).
As shown in Table 3, unit consumption
for fall-winter periods averaged approximately 0.045 gpd/sq ft, which was assumed to represent average domestic
water usage in a typical office building.
on fixture unit volumes to verify the
0.045-gpd/sq ft average domestic water
usage per working day. The most difficult
part of the analysis was to define an average office building because many factors
must be considered in the makeup of an
office environment. The characteristics
selected as average in this study are
based on data from office buildings in the
study area and from studies of other researchers, when possible. When actual
data were not available (as was the case
with internal water consumption, building maintenance water usage, and allowances for nonoffice amenities), best en-
Estimating procedure was developed
for an average office building
The second step in the analysis was to
develop a theoretical estimating procedure for an average office building based
Average
Office
Complex
TABLE
evaluation
of meter record
Summary
Building
Floor Area
sq ft x 1,000
3
for ofice
buildings
Water
Usage
gal x 1,000
Fall and
Winter*
Spring and
Summert
in study
Unit
Fall and
Winter*
Annual
area
Average
Water
Usage
gpdfw fii:
Spring
and
Summert
Annual
A
B
C
D
E
F
G
H
:
2,000
1,500
860
610
300
250
240
150
125
150
7,182
2,794
7,887
1,636
2,174
1,446
398
514
1,141
646
24,609
10,566
27,673
12,215
7,441
4,851
537
2,803
3,422
2,355
31,791
13,360
35,560
13,851
9,615
6,297
935
3,317
3,001
4,563
0.028
0.014
0.071
0.021
0.056
0.044
0.013
0.026
0.070
0.033
0.095
0.054
0.248
0.154
0.191
0.149
0.017
0.144
0.211
0.121
0.061
0.034
0.159
0.087
0.123
0.097
0.015
0.085
0.077
0.140
K
L
M
145
55
45
794
201
329
1,059
502
575
1,853
703
904
0.042
0.028
0.056
0.056
0.070
0.098
0.049
0.049
0.077
;
165
420
2,300
1,506
3,066
1,807
5,366
3,313
0.070
0.042
0.084
0.056
0.077
0.049
200
300
230
150
110
100
1,620
1,100
3,285
730
1,679
1,095
803
438
11,830
8,025
4,380
1,825
3,358
1,115
1,606
992
17,720
10,030
7,665
2,555
5,037
2,210
2,409
1,430
29,550
18,055
0.084
0.028
0.056
0.056
0.056
0.034
0.056
0.056
0.045
0.112
0.070
0.112
0.057
0.112
0.076
0.084
0.070
0.106
0.098
0.049
0.084
0.057
0.084
0.055
0.070
0.063
0.076
E
R
s
T
U
V
w
Average
*October
1 through
March 31
fApri1 1 through September
31
*Gallons per working
day per square
year
foot: assumes
130 working
TABLE
Fixture-use
Building
Characteristic
Category
AND
Total building population
Male population
Female population
Calculation
Urinals
Lavatories
Internal consumption
Service sinks
Building maintenance
Subtotal
Allowance
for nonoffice
amenities,
transients,
etc.
Total building water usage
Water usage per unit building
MANAGEMENT
200,000-sq-&o&ice
State plumbing
standards
i
area
OPERATIONS
days per
Potential savings were then estimated
The final step in the analysis was to
estimate potential savings in office building water usage through the utilization of
water-efficient
plumbing fixtures. This
was accomplished by applying the fixture-use procedure to the hypothetical
200,000-sq-ft office building and estimating domestic water usage for plumbing
fixtures conforming to pre-1980 and 1980
plumbing standards and comparing the
results with usage estimates for water-efficient fixtures.
Four cases were considered in this
evaluation. Water usage calculations for
each case are summarized in Table 5 and
depicted graphically in Figure 1.
building
Building
Characteristic
200,000 sq ft
250 sq ft/person
90 percent
Toilets
76
York
Value
Building floor area
Population
density
Occupancy
Usage
New
260 working
4
for a hypothetical
procedure
using 1980
/
days per period,
Value
720
396 (55 percent)
324 (45 percent)
Water
Used-gpd
324 women x 3.5 gal/flush
x S/day
396 men x 3.5 gal/flush
x l/day
396 men x 1.5 gal/flush
x Z/day
720 persons x 0.5 gal/use*
x S/day
720 persons x 0.25 gpcd
Estimated
Estimated
3,400
1,390
1,190
1,080
180
100
250
7,590
20 percent
1,520
9,110
0.045 gpd/sq
allowance
gineering judgment was applied to determine reasonable values. These assumptions can vary significantly and should be
considered on a site-specific basis.
For example, a hypothetical
office
building is considered, with a floor area
of 200,000 sq ft and the following average
characteristics:
l
population density-250
sq ft per
person;
l
building occupancy-90
percent;
l
gender mix-55
percent men, 45
percent women;
l
plumbing fixtures-3.5-gal/flush
toilets, 1.5-gal/flush urinals, and 3.0-gpm
lavatories;
l
lavatory usage-O.5 gal per hand
wash, based on a 3-gpm lavatory flow for
10 seconds;
l
‘internal consumption-l
qt per person per day;
l
service sinks-100 gpd; and
l
building maintenance-250
gpd.
An allowance for items such as nonoffice amenities, transient (nonoccupant) restroom
usage, and leaking
fixtures must also be applied. For the
purposes of this study, these are assumed to account for 20 percent of the
total building water usage.
When these design assumptions are
applied, the average water usage is calculated at 9,110 gal per working day (Table
4). Dividing this value by 200,000 sq ft of
floor area gives a unit water consumption
of approximately
0.045 gpd/sq ft per
working day, which is approximately
equal to the average fall-winter value determined from evaluation of the meter
record. Based on this correlation, the fixture-use procedure appears to provide a
good approximation of water consumption in office buildings and can be utilized
to evaluate the effect of water-efficient
plumbing fixtures on water consumption
in these facilities.
Case 1 examined
pre-1980
plumbing
standards
at maximum
fixture
volume.
ft
Copyright (C) 1992 American Water Works Association
Prior to 1980, plumbing standards
mitted 5.5-7.0-gal/flush
toilets,
3.0-gal/flush
urinals, and 3.0-gpm
tories. In case 1, all fixtures
assumed to have the maximum
TOURNAL
per1.5lavawere
flush
AWWA
30
I
25
i
20
I
4
15
F,
ij
3
2
10
i:
5
0
Hlqh
w
LOW D-0
Budding
Denslly
acd
occ”paney
Figure 1. Water usage for conventional
versus water-efficient fixtures in hypothetical office building (high D-O-high
population density and btklding occupancy;
low I)-O---lou! population density and building occupancy)
Mint ated domestic watw
pluntbingjktw~s
TABLE 5
usage in a lzypothetical ZOO,WOs9f? uf%ce building for watewfirimt
and futures cowforming to pw-1980 atid 1980 plumbing standards
Case I
Pre- 1980
Plumbing
Standards
(7.0-gal/flush
toilets,
Case 2
Pre- 1980
Plumbing
Standards
(5.5gal/flush
toilets,
Case 3
1980
Plumbing
Standards
(X5-gal/flush
toilets,
Gas? 4
Water-Efficient
Plumbing
Fires
(1.6.@Mluah
toil&s,
1 .O-gal/flush
urinals)
density-
sqJ?/pMil~t
orcupntKypEVS%t
_xI-_~ ---.
2
U‘%jiF--gplf
~~7.980
Total usage
mm and
wonm-@it
lntrmal
cnnwnptinngPd
Sewlce
Gnks-gpd
IWding
maintenance--
gPd
IlSajic-gpd
0
10.130’~---__l_
4.520
5.740
----
L,
.
____-
250
I10
250
140
250
140
250
100
100
100
100
1 on
100
loo
250
‘50
250
250
250
250
18.710
10.7so
250
250
14 . Z’W
b
x.210
10,420
6.050
5,740
3,390
I
Subtotal
Allowatw
’
140
100
for
*Hi& tlcnsity and occupancy
+l*w density and occupancy
$hl-men,
W-won~rn
OcTOBr3?
1992
Copyright (C) 1992 American Water Works Association
I’J BEHLING
C N.J. WAlfI‘IIIKCI
77
TABLE
6
Potential water savings using water-eficientfultures
in a hypothetical 200,000sq-ft
ojice building
Potential
water
With Water-Efficient
Water
Building
Type*
High D-O
Imv D-O
Pre-1980
Fiires
17,060~22,450
9,850-12,900
*High D-O-high
building occupancy
population
Usage-gpd
1980
Fiitures
12,500
7,260
density
6,890
4,070
and building
2, all fixtures were assumed to have the
lowest flush volumes required under pre1980 standards (5.5-gal/flush toilets and
1.5-gal/flush urinals). As in case 1, lavatory usage was estimated to be 0.5 gal per
hand wash.
Case 3 examined
1980 plumbing
standards for fixtures. The 3.5-gal/flush
toi-
lets, 1.5-gal/flush urinals, and 3.0-gpm
lavatories
required
under the 1980
plumbing standards were used in case 3.
As in cases 1 and 2, lavatory usage was
estimated to be 0.5 gal per hand wash.
fixtures.
Water-efficient
plumbing fixtures (1.6gal/flush toilets, l.O-gal/flush
urinals,
and 2.0-gpm lavatories) were used for
case 4. Lavatory usage was estimated at
0.33 gal per hand wash based on a 2.0gpm lavatory flow for 10 seconds.
To account for some of the site-specific
factors that can affect domestic water
usage in an office building, a range of
estimates is presented for each case in
Table 5. The upper and lower ends of
each range are defined as follows:
l
high D-O-high
population density
(200 sq ft/person)
and building occupancy (100 percent); and
l
low D-O-low
population density
(300 sq ft/person)
and building occupancy (85 percent).
Other building characteristics
assumed in the development of Table 5 are
similar to those used for the average office building in Table 4, including gender
demographics (55 percent men, 45 percent women); internal consumption (1
quart per person per day); service sinks
(100 gpd); building maintenance
(250
gpd); and an allowance for such items as
nonoffice amenities and transient restroom usage (20 percent of the total water
usage). To simplify the analysis, these
characteristics were held constant for all
cases considered in the evaluation.
78
MANAGEMENT
AND
OPERATIONS
wd
10,170-15,560
5,780-8,830
occupancy;
Case 2 examined
pre-1980
plumbing
standards at lowest flush volumes. In case
water-efficient
Compared
Pre-1980
WaterEfficient
Fiitures
volumes permitted under pre-1980 standards (7.0-gal/flush
toilets and 3.0.
gal/flush urinals). Lavatory usage was
estimated to be 0.5 gal per hand wash,
based on a 3.0-gpm lavatory flow for 10
seconds.
Case 4 examined
Savings
Fixtures
low D-O-low
With
Fixtures
~
Compared
With
1980 Fixtures
percent
gpd
percent
60-69
59-68
5,610
3,190
45
44
population
density
and
Based on the fixture-use procedure,
domestic water usage for the 200,000sq ft office building using plumbing
fixtures conforming
to pre-1980 standards ranged from 9,850 to 22,450 gpd
(cases 1 and 2). Using plumbing fixtures conforming
to 1980 standards,
water usage in the building ranged
from 7,260 to 12,500 gpd (case 3).
When water-efficient
fixtures were considered, domestic water usage ranged
from 4,070 to 6,890 gpd (case 4).
Water-efficient fixtures
can reduce consumption
Installation of water-efficient plumbing
fixtures
(1.6-gal/flush
toilets,
l.Ogal/flush urinals, and 2.0.gpm lavatories)
has the potential to significantly reduce
water consumption in office buildings. As
shown in Table 6 for high density-occupancy conditions, water-efficient fixtures
can reduce water usage by as much as 69
percent compared with pre-1980 standard plumbing fixtures (5.5. and 7.0gal/flush toilets, 1.5- and 3.0.gal/flush
urinals, 3.0-gpm lavatories) and as much
as 45 percent compared with plumbing
fixtures conforming to 1980 plumbing
standards
(3.5-gal/flush
toilets, 1.5gal/flush urinals, 3.0-gpm lavatories).
Under low density-occupancy
conditions, water usage can be reduced by as
much as to 68 percent compared with
pre-1980 fixtures and 44 percent compared with those conforming
to 1980
plumbing standards.
In addition, unit water consumption
values used to project water usage in proposed office buildings should be revised
to reflect the post-1992 requirement of
water-efficient
fixtures in New York
State. Published water consumption values for office establishments range from
0.70 to 0.084 gpd/sq ft7 Based on the
analysis discussed here, a value of between 0.020 and 0.034 gpd/sq ft per
working day (as shown in Table 5) is
suggested for projecting domestic water
usage in proposed office buildings constructed with water-efficient fixtures, exclusive of air conditioning and irrigation.
The theoretical estimating procedure
discussed here can be utilized to esti-
Copyright (C) 1992 American Water Works Association
mate potential water savings in office
buildings through the use of water-efficient plumbing fixtures; however, it is
important to note the limitations of the
procedure. Foremost, the procedure is
hypothetical and includes many assumptions specific to the study area. Further
study is recommended to document the
water savings projected in this study with
field data. In addition, it is important to
consider the following when estimating
water consumption in office buildings:
l
local factors such as population density, building occupancy, and gender demographics
directly affect domestic
water usage and must be viewed on a
case-by-case basis;
l
irrigation and cooling water usage
must be evaluated for each site and
added to domestic water consumption estimates; and
. significant nonoffice areas (large
restaurants, health clubs, and large retail
establishments),
which are sometimes
incorporated into office environments,
must be evaluated on a site-specific basis.
Acknowledgment
The authors acknowledge the assistance of the water departments of the
Town of Hempstead, N.Y., and the Village of Garden City, N.Y.; and the water
districts of Manhasset-Lakeville,
N.Y.,
and Jericho, N.Y., which provided the
meter record data used in this study.
References
A. Water-Use
Efficiency
Standards
for Plumbing
Fixtures:
Benefits
of National
Legislation.
Jour. AWWA,
82:5:51
(May
1990).
McKinney’s
Consolidated
Laws ofNew
York,
Book
17-l/2-Environmental
Conservation
Law, sec. 150314.
State of New York-Ojjicial
Compilation
of
Codes, Rules and Regulations,
Subchapter
B-Building
Construction,
Part 765.8.
Long Island
Business
News.
Long Island
Almanac,
(1989, 1991).
KONEN, T.P. Water
Use in Office Buildings.
Plumbing
Engr. uuly 1986).
PKES~OP*‘, B.L. High-Efficiency
Water Closet
Analysis.
Plumbing
Engr. Uune 1987).
James
M. Montgomery,
Consulting
Engineers. Water Treatment
Principles
and Design. John
Wiley
and Sons,
New York
(1985).
1. VICIGXS,
2.
3.
4.
5.
6.
7.
About
the authors:
Patrick J. Behling is an
environmental
engineey with Dvirka and
Batiilucci
Consulting
Engineers,
6800 Jericho Turnpike,
Syosset,
NY
11791.
He
is
a
graduate of the University of Dayton, Dayton, Ohio (BCE), and
Manhattan
College, Riverdale, N.Y. (ME
Env.), and is a member ofAWWA,
ASCE,
and WEF. Nicholas J. Bartilucci
is the managingpartner
ofDvirka and Bartilucci
Consulting Engineers.
JOURNAL
AWWA