xvEPA
United States
Environmental Protection
Agency
Office of Water
Washington, D.C.
EPA 832-F-00-047
September 2000
Waste water
Technology Fact Sheet
High-Efficiency Toilets
INTRODUCTION
In 1992, Congress passed legislation requiring that
all toilets sold in the United States meet a new
water conservation standard of 1.6 gallons per flush
(gpf). By 1992, in response to the growing need for
conservation of drinking water supply resources, a
number of metropolitan regions and 17 states had
already instituted water conservation programs
which included high-efficiency toilet requirements.
A national water use standard for a high-efficiency
toilet was necessary to address the problems with
different states and communities having established
different toilet water use standards. A national
standard eliminated the need for plumbing fixture
firms to manufacture, stock, and deliver different
products, and the difficulty for states in preventing
the importation of high-water-use fixtures.
High efficiency designs have significantly improved
since they were first introduced. Despite the
improvements, the industry continues to refine this
technology. Based on consumer surveys, the
majority of users are satisfied with the performance
of the current designs.
Because toilets use is the largest proportion of
indoor water used in a household, high-efficiency
toilets achieve real water savings.
The national high-efficiency toilet standard brings
a range of questions and concerns for. This fact
sheet is intended to assist in answering the
questions that the consumer, property manager,
plumbing contractor, and utility manager might
have about the high-efficiency toilet standards.
ENVIRONMENTAL, PUBLIC, AND
CONSUMER BENEFITS
Studies indicate that converting to water efficient
toilets, showers and clothes washers, results in a
household water savings of about 30% compared to
conventional fixtures. A change to high-efficiency
toilets alone, reduces toilet water use by over 50%
and indoor water use by an average of 16%. This
translates into a savings of 15,000 to 20,000 gallons
per year for a family of four. Furthermore, more
efficient plumbing products result in lower
wastewater flow and increase the available capacity
of sewage treatment plants and onsite wastewater
disposal systems.
The general public also benefits directly from water
conservation measures. Practiced on a wide basis,
efficient use of water resources helps reduce the
potential need during drought periods for water
restrictions such as bans on lawn watering and
car-washing. Savings to the consumer from lower
water bills, depending on local water rates and
actual use, can range from $50 to $100 per year.
Many hotels, motels, and office buildings are
finding that new fixtures are saving them 20 percent
on water and wastewater costs.
DESCRIPTION OF THE TECHNOLOGY
The principles of high-efficiency toilet design and
operation reflect the shift from remvoing waste by
using flushwater volume to increasing flushwater
velocity to remove waste.
The design of the bowl contour became more
vertical design to achieve the necessary increased
downward velocity. Nevertheless, the bowl contour
must ensure a shallow but large water surface
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towards the front of the bowl for adequate waste
immersion. Many consumers notice that
high-efficiency bowl designs result in a flush that
tends to swirl less than their previous toilet. This
is because the drag, or friction, resulting from
swirling water reduces the essential velocity.
Some manufacturers use an enhanced front jet
towards the bottom of the bowl to assist in waste
removal. But other toilets that have received top
consumer survey ratings use no jet at the bottom.
Gravity-flow or pressure-assisted?
Two types of technology are available for both
residential and commercial uses. The most widely
available is a high-efficiency modification of the
conventional gravity flow toilet. The other, the
pressure-assisted toilet, utilizes pressurized air in
the tank to achieve additional force.
The choice between gravity and pressurized toilets
usually hinges on two factors: noise, and the
distinction between whether the maintenance is
provided by the homeowner or by a building
manager. Pressure-assisted toilets are much less
likely to clog than even the older, 3.5 gpf gravity
toilets. While many of the more recent models of
high-efficiency gravity toilets perform as well as
pressure-assisted models in tests, maintenance
issues for heavy-duty use, or responsibility for
maintaining multiple toilets, may lead to the
decision to install pressure-assisted toilets. Some
states, such as New Jersey, require pressure-assisted
toilets in commercial use.
Gravity toilets in buildings with cast-iron waste
lines may clog more readily, because of the
roughness of the interior of the pipe. New
buildings use PVC pipe, through which waste flows
more easily. Choosing pressure-assisted toilets for
buildings served by cast-iron pipe may reduce
maintenance needs.
However, the greater noise from pressure-assisted
toilets is a factor to consider when locating toilets
near sleeping or working quarters. And the
pressure-assisted toilet is generally more costly than
gravity-flow.
Gravity-flow toilets achieve the necessary enhanced
water velocity largely through coordinated
improvements of the siphoning features of the
fixture. Indeed, some of the early experiences with
high-efficiency toilets that clogged too easily were
the result of designs that increased siphoning by
choking down on the trap size. Manufacturers
responded by re-sizing the trap diameter nearer its
original dimensions, and instead are coordinating
the rim dimensions, bowl contour, and trap size to
work in concert to enhance the force of the water
and the siphoning function.
Pipe slope standards
The issue has been raised as to whether existing
pipe slope standards are adequate to carry these
reduced flows. American Society of Mechanical
Engineers (ASME) tests indicate that the existing
standards exceed performance requirements for
drainline carry minimums. Field studies similarly
report very few complaints, representing problems
with a few individual buildings. The standards are
under constant review, and any changes indicated
would be recommended through normal
procedures.
HIGH-EFFICIENCY TOILET
PERFORMANCE
Consumer surveys, performed by utilities that have
been implementing high-efficiency toilet programs
(such as rebates), have shown that the vast majority
of 1.6 GPF, high-efficiency toilets work well. For
example, 90 percent of San Diego, CA, customers,
and 95 percent of Austin, TX, customers reported
that they were "satisfied" or "very satisfied" with
their high-efficiency toilets; 91 percent of Tampa,
FL, ratepayers said they would purchase the 1.6
gallon toilet again. A review of multiple
metropolitan area customer satisfaction surveys for
the 1995-1998 period shows that, while
performance among individual high-efficiency
toilet models varied, the large majority were rated
at least satisfactory in performance, with most rated
better than satisfactory.
Some brands and models have drawn more positive
responses from consumers than others, with specific
models being withdrawn and added as research and
design progress. Since 1992, when the national law
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was first passed, plumbing products have gone
through several cycles of improvements, with each
new generation bringing improved product
performance and customer acceptance. The
marketplace has responded to the move to the
high-efficiency toilet standard so as to better serve
customer requirements.
The two complaints most often made against the
high-efficiency fixture are somewhat more frequent
clogging, and the perceived need for more frequent
double-flushing. A 1996 survey in New York City
on customer satisfaction reported that building
managers—who are responsible for maintaining a
number of toilets-reported more frequent clogging,
probably due to the smaller trap size of the toilet
(designed to increase siphoning). The
high-efficiency toilet designs, as discussed in the
section on operation and maintenance, cannot
accommodate extraneous waste materials and
non-flushables such as paper towels. Building
managers should communicate this to their tenants.
In a study of 100 homes in each of 12 North
American cities, the incidence of double-flushing
was virtually the same for homes with high-
efficiency toilets as for those with conventional
toilets.
LIMITATIONS
The consumer choice of a particular high-efficiency
toilet model must take into account the specifics of
the application. Key considerations include:
• To be sure the new toilet will cover the
area, check the dimensions of the space in
which the toilet is to be installed, including
the 'footprint' of the old toilet.
If the drainlines are made of cast-iron rather
than PVC pipe, the toilet may be more
likely to clog. Ensure adequate
maintenance, or consider a pressure-assisted
model.
Pressure-assisted models tend to be more
noisy than gravity-flush, so use caution
when installing this type adjacent to
sleeping quarters.
Ensure the availability of electricity for
electric-assisted models.
• Some toilets have a taller seat height, which
should be evaluated based on anticipated
users (some higher seats will be less
accessible to children).
• Users in areas with high mineral content in
the water should check rim hole
dimensions, or consider a toilet with a
holeless rim.
CONSUMER TIPS
Purchase: The buyer of the high-efficiency toilet
should carry out the same type of research
necessary for any significant purchase intended to
be used for a long time. Refer to current issues of
consumer magazines that evaluate water-efficient
toilets (frequently under article listings for water
conservation fixtures). Your water utility,
individual plumbers, and the local plumbers' union
or association may also be able to recommend
certain models. Look for manufacturers'
guarantees. By following these tips, purchasers of
water conservation toilets can be fairly assured of
getting a satisfactory product.
Installation: Proper installation is especially
important for high-efficiency toilets. Licensed
plumbers who guarantee their work will make sure
fixtures are installed correctly. It is very important
to follow the manufacturer's instructions. The
proper flow cycle for high-efficiency toilets is
shorter—usually about 45 seconds—than previous
models.
If installing a water-conserving toilet to replace an
old one, use new mounting bolts of the proper
length, and be sure the old wax seal is completely
removed before installing the new one. Check and
clear drain lines while accessibility is open.
Operation and Maintenance: The common advice
"Don't use your toilet as a trash bin" is especially
important. High-efficiency toilets will not perform
well if non-flushables, such as paper towels, are
sent down the fixture. There has always been a
need for plungers and plumbing "snakes," and their
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use should be considered first when the toilet
overflows or does not refill completely.
Since flapper valves require replacement about
every five years, proper selection of replacement
valves is a key maintenance consideration. A study
conducted by the Metropolitan Water District of
Southern California found that proper flapper valve
model selection is essential for continued
performance. Of the physically compatible
replacement flapper valves, half the models left a
toilet with less than 1.6 gpf—and the resulting
incomplete flush had insufficient water to do the
job the toilet was designed to do. Since most
hardware stores can stock only a few brands, there
is no guarantee of compatibility. Industry standards
groups are working to insure that after-market
flappers will perform properly. Getting the right
replacement flapper value is worth the effort.
A key problem affecting 1.6 gpf toilets is a result of
the use of chemical in-tank toilet cleaners. All U.S.
toilet manufacturers recommend against the use of
chemical in-tank toilet cleaners, as the strong
chemicals degrade the works within the toilet.
Even with current toilets that include
chemical-resistant materials, chemical cleaners still
increase the specific gravity of water and slow
flushing velocity, interfering with performance.
NOTE: Most major toilet manufacturers maintain
1-800 number Consumer Hotlines (call the
distributor or 1-800-555-1212). These hotlines are
set up to address both non-technical and technical
questions relating to installation, operation, and
maintenance of high-efficiency toilets.
COSTS
A wide range of toilets that perform well are
available in all price ranges, although very
inexpensive (less than $100) imports may not carry
the American National Standards Institute (ANSI)
design standard (different from the water
conservation 1.6 gpf standard) and not function
properly. In most cases, there is little relationship
between price and performance. The consumer
choice recommendations listed above under
"Limitations" will help customers select the right
model for them.
The choice to retrofit based on cost recovery from
water savings can be easily calculated at the local
level based on water rates and the price of the toilet.
For average water/sewer rates, household savings
for a typical four-person household is about
$50/year.
REFERENCES
Other Related Fact Sheets
Other EPA Fact Sheets can be found at the
following web address:
http://www.epa.gov/owmitnet/mtbfact.htm
1. Austin, TX "Common Questions and
Answers about 1.6 gpf Toilets." Internet
site at:
[http://www.ci.austin.tx.us/watercon/toilet
q.htm].
2. Consumers Digest, July/August: 51-52;
Geary, D., 1997. Low-Flush Toilets.
3. Consumer Reports, "Low-Flow Toilets".
February, 1995: 121-124.
4. Consumer Reports, "In Search of a Better
Toilet." Internet site at
[http://www.consumerreports.org/
Categories/YourHome/Reports/9805toi0.h
tm].
5. DeOreo, W.B., P.W. Mayer, and P. Lander.
Evaluating Conservation Retrofit Savings
With Precise End-Use Data. 1998 Annual
Conference, Water Resources, Vol. B - (2 of
5 Volumes) June 21-25, 1998, pp. 479-505,
Dallas, Texas
6. Koeller, J. M., W.P. McDonnell, and H.O.
Webster, III. After-Market Replacement of
Flush Valve Flappers in Ultra-Low-Flush
Toilets: A Study of Compatibility and Flush
Volumes.
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7. National Trade Association of Plumbing
Products Manufacturers, April 1998. Press
Release. Report Credits Low-Flow
Plumbing Products with Saving Water and
Satisfying Customers. Glen Ellyn, Illinois.
The mention of trade names or commercial
products does not constitute endorsement or
recommendation for use by the U.S. Environmental
Protection Agency.
Nelson, J.O., N. Orrett, and J. Weber. A
"Choice" ULF Toilet Replacement Strategy.
1996 Annual Conference, Water Resources,
June 23-27, 1996, pp. 175-197, Toronto,
Ontario, Canada.
10.
Osann, E.R. and I.E. Young. April 1988.
Saving Water, Saving Dollars: Efficient
Plumbing Products and the Protection of
America 's Waters. Prepared for American
Council for an Energy-Efficient Economy,
Washington, D.C.
Peak International, April 1996. Ultra Low
Flush Toilet Program, Customer
Satisfaction Surveys. Prepared for the
Metropolitan Water District of Southern
California.
11. Plumbing-Heating-Cooling Contractors
(PHCC) - National Association. 1996.
"Water Conservation". Falls Church,
Virginia.
12. Swaffield, J.A. and L.S. Galowin. "Solid
Waste Transport Design Requirements.
Design Engineering Charts for Drainage
System Pipe Sizing". Research Proposal to
the American Society of Plumbing
Engineers Research Foundation. Heriot-
Watt University, Edinburgh, Scotland.
13. Water Resources, 1998 Annual Conference,
Vol. B - (2 of 5 Volumes) June 21-25, 1998,
pp. 165-173, Dallas, Texas.
14. Wirthlin Group, October 1995. A Survey of
Ultra-Low-Flush Toilet Users. Prepared for
The Los Angeles Department of Water and
Power.
For more information contact:
Municipal Technology Branch
U.S. EPA
Mail Code 4204
1200 Pennsylvania Ave., NW
Washington, D.C., 20460
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MUNICIPAL TECHNOLOGY
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