Toilet Fixtures Introductiontoilet1



Toilet fixture replacement has been a staple of the water industry’s initiatives to reduce potable water consumption since the late 1980s.  It still represents one of today’s most popular water efficiency initiatives, as the first “program of choice” by water providers embarking on their initial foray into hardware-related conservation.  In these programs, older 3.5- and 5.0-gallons per flush (gpf) [13 litres per flush (Lpf) and 19 Lpf] toilet fixtures in residences are replaced with 1.6-gpf (6 Lpf) or 1.28-gpf (4.8 Lpf) fixtures.  Today, some water providers with aggressive replacement programs are already approaching a level of “saturation” in their residential sector wherein the majority of toilet fixtures are the efficient models.  Therefore, a number of water providers have moved on to other more efficient products and higher priorities in their conservation programs.

Density of Use - Residential

As the number of bathrooms in housing steadily increases, and, in some cases, the number of occupants decreases, development of cost effectiveness information related to toilet replacement programs must address just which toilets within a residence should be replaced, e.g., all of them, the most-used toilet, the oldest toilet, the toilet with the highest flush volume, or some other replacement criteria.  To aid in this analysis, we have compiled some national numbers on toilet “density” in residential housing.  Download the table that shows the increase in density during the period from 1970 to 2003. 

Types, Technologies, and Definitions

Two distinct types of toilet fixtures dominate the marketplace today: ULFTs (Ultra-Low Flush Toilets – aka “low flow” or “ultra-low-flow”) and HETs (High-Efficiency Toilets).  ULFTs are defined by an effective flush volume in the range between 1.28-gpf and 1.6-gpf (4.8 Lpf and 6.0 Lpf), while HETs are defined as 1.28-gpf (4.8 Lpf) or less.  View the prevalence of HETs in the North American marketplace here. 

Several different technologies are used by the manufacturers to achieve these efficient flush volumes.  Those technologies are NOT all equal in flush performance nor cost.  The following sections provide information on both technologies.

Ultra-Low-Flush Toilets (ULFTs)

ULFTs are defined as fixtures that have a maximum average flush volume not exceeding 1.6-gallons-per-flush (6 Lpf). Such fixtures have existed elsewhere in the world for more than two decades.  ULFTs began making their way into U.S. homes in the 1980s.  Beginning with Massachusetts in 1989, ULFTs began to be mandated by various local and state jurisdictions.  Subsequent to Massachusetts, 15 other states and 6 local jurisdictions mandated that all toilets sold and installed be ULFTs.  This prompted the U.S. Congress (with the support of the plumbing industry and water purveyors) to take the requirement national, and the Environmental Policy Act of 1992 (EPAct 92) mandated that all toilets sold in the U.S. (with a few minor exceptions) be ULFTs.

The EPAct 92 mandate became effective on January 1, 1994 (with some exceptions for commercial applications) and pre-empted all of the previously legislated state and local mandates on toilet flush volumes (pre-emption has since been withdrawn by the U.S. Department of Energy).  Hence, ULFTs have been the U.S. “law of the land” for 15 years.

In Canada, current law allows for the continued sale and installation of 13 Lpf (3.5 gpf) fixtures, the only provincial exception being Ontario, where new construction is subject to a 6 Lpf (1.6 gpf) maximum for toilet fixture flush volume.  However, for fixture replacement in existing Ontario installations, the maximum flush volume remains at 13 Lpf.  Other flush volume limits exist locally in a few communities in British Columbia.

High-Efficiency Toilets (HETs)

The HET is defined as a fixture that has an effective flush volume of 20 percent below the 1.6 gpf (6.0 Lpf) U.S. maximum or less, equating to a maximum of 1.28 gpf (4.8 Lpf). (Note: The HET category includes dual-flush fixtures, which have been determined to meet the volume requirement by defining the effective flush volume as the average volume achieved with one full flush and two reduced flushes.)

The 20 percent reduction threshold serves as a metric for water authorities and municipalities implementing aggressive toilet replacement programs (using HETs) and, in some cases, establishing an additional performance tier for their financial incentives (e.g., rebate and voucher programs). It is also a part of the water-efficiency element of many green building programs in the U.S. and Canada.

HETs have been available in the marketplace in California and other parts of the West since 1999.  Today, 73 different toilet brands offer over 1,300 HET models of tank-type fixtures!  Of the 1,300, dual-flush models amount to 500 and single flush are 800.  For flushometer valve-bowl toilets, approximately 230 HET combinations are available from 15 manufacturers.

The U.S. Environmental Protection Agency’s WaterSense Program specification for toilets includes only HETs and provides for certification of HET models against a rigorous set of performance requirements.

HETs are not a new phenomenon, but have existed in the North American marketplace for 12 years. During that time, new fixture models have been introduced and, most importantly, the performance of HETs has improved dramatically.  Today, HETs outperform their ULFT (1.6 gpf/6.0 Lpf) predecessors as well as the 3.5 gpf/13 Lpf toilets that were installed in the 1980s.

Do sensor-activated flush valves save water?

Before beginning this discussion, it is important to note that the growth of the "touchless restroom" has been in large part due to the concern for hygiene and health, since fixtures do not need to be touched with the hand in order to activate flow.  In the past several years, sensor-activated flush valves have been a topic of much conversation.  Most water efficiency practitioners readily acknowledge that these devices (sensors for commercial toilet fixtures) save no water.  In fact, they would quickly say that these devices waste water by flushing more frequently than necessary!  The following study confirmed that fact:

Hillsborough County Florida 

Concluding in 2009, Veritec Consulting, Inc. and Koeller and Company conducted an extensive fixture replacement study in a major commercial office building wherein manually activated faucets and flush valves were replaced with sensor-activated units.  This study took place over a two-year time period, was comprised of 4 phases, and used dataloggers to determine what changes in water consumption resulted from such replacements.

After an extensive period of baseline measurement (pre-monitoring), the study analysis showed that the replacement of manually operated commercial toilet flush valves with sensor-activated valves resulted in a 54 percent increase in water consumption!  For urinals, water use dropped by a small amount.

Gauley and Koeller (2010) Sensor-Operated Plumbing Fixtures, Do They Save Water? 

Dual-Flush Retrofit Devices

Can a conventional single-flush toilet be ‘converted’ to dual-flush with a kit or a device?  Do such devices affect toilet performance?  Go here for more information.

Following are some of the related documents that may be useful:

A.  Koeller and Company (2011) High Efficiency Plumbing Fixture Direct Install Water Savings Analysis -- A report on water savings from high efficiency toilet retrofits in residential and commercial applications for California's Sonoma County Water Agency. 

B.  Koeller and Company & Veritec Consulting Inc. (2011) Evaluation of Water Use Reduction Achieved Through Single-Family Residential Toilet Fixture Replacements -- A report on the water savings and customer satisfaction with Niagara Stealth 0.8 gallon (3 Liters) vacuum assisted toilet fixtures installed in older homes in Southern California.  

C.  Koeller and Company & Veritec Consulting Inc. (2011) Evaluation of Water Use Reduction Achieved Through Multi-Family Residential Toilet Fixture Replacements -- A report on the water savings and maintenance service calls associated with replacement of 192 aging 3.5 gallon (13 Liter) fixtures with 1 gallon (3.8 Liter) pressure-assist toilet fixtures in a downtown San Francisco apartment building.  

D.  List of WaterSense tank-type HET fixtures (2011) - The recent explosion in the number of models of HETs has led to listing all of the fixtures that currently appear to be qualified to use the WaterSense designation. This list is periodically updated as new models are introduced or older models are dropped from product lines. You may also download a list of the Flushometer Valve HET combinations.  

E.  Koeller and Company & Veritec Consulting Inc. (2009) Evaluation of Water Use Reduction Achieved Through Hotel Guest Room Toilet Fixture Replacements Parc 55 Union Square Hotel San Francisco, CA - A report that demonstrates significant water savings through a luxury hotel high-efficiency toilet (HET) retrofit of over 1,000 guest room toilets at the Parc 55 Union Square Hotel in downtown San Francisco, CA.

F.  Koeller, J. (2008) A Bit of Plumbing History - A quick 1-page summary of key milestone dates from 1989 to 2008.

G.  Koeller J. (2007) Definitions of HET and HEUWaterSense HET specification - The definition of an HET as contained within the California code and as defined by WaterSense.

H.  UNAR HETs - A list of HETs that meet or exceed the 350 gram waste removal performance threshold of the Maximum Performance (MaP) testing protocol AND meet the durability requirements of the Supplementary Purchase Specification (SPS).  These fixtures have all been independently tested and found to comply with the Uniform North American Requirements (UNAR) for toilet fixtures.

I.  Customer Satisfaction with HETs: The question of customer satisfaction with HETs at their lower flush volumes has been asked repeatedly over the past few years. Will customers accept the noise of the flush action associated with a pressure-assist HET? Will customers use the dual-flush features on those HETs as intended? Do HET users experience any "double-flushing"? Will there be any reports of drainline problems due to reduced water flows? Answers to some of these questions (and others) are beginning to surface as water providers survey their customers in connection with their ongoing HET programs. Three recent presentations shed some light:

(1) The Santa Clara Valley Water District (San Jose, Calif) replaced over 1,000 water-wasting toilets in commercial applications with pressure-assist HETs (1.0-gallons per flush and less). Presentation that describes the program and anecdotal customer satisfaction findings.

(2) Redwood City, Calif has replaced over 5,000 water-wasting toilets in RESIDENTIAL dwellings, including both dual-flush Caroma HETs, pressure-assist 1.0-gallon HETs, and a few 1.6-gallon ULFTs. Presentation for program information and customer satisfaction statistics.

(3) Elsinore Valley Water District and Eastern Municipal Water District replaced aging toilets with 0.8 gpf (3.0 Lpf) gravity fed toilets in pilot study homes.  In addition to determining water savings as a result of those replacements, a customer satisfaction survey was also performed.

J.  Koeller, J. (2005) Potential Best Mgt Practice Report HETs HEUs - An analysis of the installed base of residential and non-residential toilets in California was completed in 2005, along with the potential for additional water savings through fixture replacement with HETs and HEUs.  The report examines the potential water savings that might result from implementing various program scenarios directed at replacing some or all of the existing installed base and/or focusing entirely on new construction. In certain instances, findings for California may be extrapolated and applied to other geographic areas.

K.  Mohadjer, P. (2003) Residential Ultra-Low-Flush Toilet Replacement Program - The Jordan Valley Water Conservancy District installed 275 new toilet fixtures in residential dwellings and then measured the water savings and customer satisfaction.  The study documents a very detailed comparison among the three quite different toilets.

L.  Dual-Flush High-Efficiency Toilet (HET) Fixtures:  Five authoritative field studies measured the water savings resulting from the installation and use of dual-flush high-efficiency toilet fixtures. This paper summarizes the results of those studies with respect to dual-flush toilet use.

Koeller, J. (2002) Dual Flush Toilet Fixtures - Field Studies and Water Savings 

The five field studies may each be downloaded individually:

Sullivan G. et. al. (2001) SWEEP - A Summary of Energy and Water Savings 

- Sullivan G. et. al. (2001) SWEEP appendix_b fixture specifications 

Sullivan G. et. al. (2001) SWEEP program equipment findings appendix d  

- Veritec (2002) Dual-Flush Toilet Project 

Aquacraft (2000) Seattle Single-Family Retrofit Study 

Aquacraft (2003) EBMUD Single-Family Retrofit Study 

Mohadjer, P. (2003) Residential Ultra-Low-Flush Toilet Replacement Program  

Toilets and Transporting Waste in Drainlines

The discussion and debate over waste transport (from toilets) in drainlines has been going on for many years. Some plumbing engineers and plumbers contend that even 1.6 gallons (6.0 L) of water is insufficient to move waste in conventional drainline systems. They further state that, because of this lack of sufficient water, waste stops moving in the drainline before it reaches the sewer, thus leading ultimately to line blockages. This becomes even more important as flush volumes are reduced below 1.6 gpf (6.0 L) to the now-popular HET threshold of 1.28 gpf maximum (4.84 Lpf).

Plumbing Efficiency Research Coalition (November, 2012) - The Drainline Transport of Solid Waste in Buildings.   PERC released The Drainline Transport of Solid Waste in Buildings report in November 2012.  The study provided important insights into the performance of long buildings building drains that can be found in commercial buildings, and highlighted needs for future research.  For more information click here.

AWE (2011) The Impacts of High-Efficiency Toilets on Plumbing Drainlines and Sewers - This article addresses key questions and concerns-as well as misperceptions-about the impacts of reduced water use and wastewater flows from water-saving measures, particularly high-efficiency maximum 1.28 gpf toilets, on plumbing sanitary drainlines in buildings and municipal sewer systems 

Non-Residential HETs and Drainline Carry - Bill Gauley and John Koeller issued a "Caution Statement" in 2009 in which they outline the conditions under which HETs probably should and shouldn't be used in non-residential applications.  This is part of on-going research on this important topic.  AWE will post further information, clarification, and recommendations as more information becomes available. 

Gauley, B. and J. Koeller (2005) Evaluation of Water-Efficient Toilet Technologies to Carry Waste in Drain Lines - As a consequence of the claims by those involved in plumbing system design and with a desire to inform their constituency on this subject, eight Canadian organizations sponsored the "Evaluation of Water-Efficient Toilet Technologies to Carry Waste in Drainlines." Those organizations were: Canada Mortgage and Housing Corporation, the cities of Calgary and Toronto, the province of Manitoba, the regions of Peel, Waterloo, and Durham, and the Ontario Ministry of Municipal Affairs and Housing.

White, G. et. al. (2005) Waste Transport in Piping Systems - In addition, with funding support from the U.S. Department of Energy, Texas A&M's Energy Systems Lab also conducted a drainline transport study. The final study report was released in 2006. 

World Plumbing Review (2007) Testing Times Down Under - Low Flow Toilets and Drainline Carry - An article in a 2007 issue of World Plumbing Review (Issue 1, 2007) covers extensive drainline waste transport testing performed in Australia.  Once you get through some of the sales "pitch" for a manufacturer’s products, there are some interesting observations in this article. 

EPA (2006) WaterSense Drainline Carry Testing Results - As part of the analyses conducted on behalf of the U.S. Environmental Protection Agency's WaterSense Program, additional drainline testing was performed to establish that WaterSense HETs were, in fact, suited to residential applications. This testing regime used the same testing media as the Canadian residential drainline study described above.

Environment Agency (2006) Impact of reductions in water demand on wastewater systems - A detailed report from the UK on the impact of water efficiency (particularly toilets) on wastewater transport and treatment.  Good coverage of this topic.

Voluntary Specifications and Test Protocols

The following four sets of specifications and testing protocols were developed by water provider interests. Compliance by manufacturers with each one is voluntary.

1) UNAR–Uniform North American Requirements for toilet fixtures 

2) SPS – SUPPLEMENTARY PURCHASE SPECIFICATION for toilet fixtures - Los Angeles Department of Water and Power's Supplementary Purchase Specification (SPS) for Toilet Fixtures (Applies to both ULFTs and HETs).  The SPS has been applied to toilets purchased, rebated, or installed in a variety of water conservation programs in North America.  However, it should be noted that compliance with the specification by toilet fixture manufacturers is entirely voluntary. It was initially adopted as specification in 2000 and covers several important items:

  • Durability of the toilet flapper when exposed to chlorine-based bowl cleaning tablets (bleach)
  • Marking of the flapper or other tank component with the part no. of the flapper and the necessary contact information for securing a replacement flapper
  • Adjustability of the tank trim such that the maximum flush volume of ULFTs shall not exceed 2.0 gallons (7.6 L) when all parts are adjusted to their maximum level and the water level is set to the top of the overflow tube

NOTE: The provisions in the SPS relating to flapper durability and marking of essential repair information inside the tank have been incorporated into the ASME/ANSI A112.19.5 U.S. national standard and apply to all tank-type gravity-fed toilet fixtures sold and installed in the U.S. 

3) MaP – MAXIMUM PERFORMANCE testing of toilet fixtures -  Maximum Performance (MaP) provides the latest information on toilet fixture performance in several reader-friendly formats!  Over 2,400 toilet fixture models (tank-type and flushometer valve/bowl combinations) are listed with their MaP flush performance scores and physical characteristics!  Go to the MaP website for more information and a 'search tool' enabling you to find just the toilet needed for your home or business. 

4) U.S. Environmental Protection Agency - WaterSense - The U.S. EPA implemented its new WaterSense product labeling and market enhancement program by introducing HETs as the first product to be labeled. The WaterSense specification for HETs incorporates most of the elements of UNAR, including MaP testing to a 350 gram minimum threshold of performance.

To view the EPAs fact sheet on HETs, click here.

To download the FINAL HET specification, visit here.

To download the latest listing of WaterSense-certified HETs, click here.

Plumbing Standards & Certification Testing

Veritec (2007) Evaluation of Toilet Test Media - This laboratory study evaluated the current testing media used in the U.S. and Canada to certify toilet fixtures for sale and installation here.  Testing with sponges and plastic balls and pellets are required in the harmonized U.S. and Canadian plumbing standards, but how realistic is any test that uses such materials to test for flush performance? This study report is a first scientific step in examining how test results using these materials compare with those obtained through MaP testing.

Other Studies

Veritec (2005) Testing of Popular Flushometer Valve-Bowl Combinations - While there had been considerable research into the performance and water savings related to residential toilet fixtures (typically gravity-fed), little work has been completed as of 2005 on flushometer valve fixtures for commercial applications. This flushometer testing program included flush volume and performance testing of seven popular commercial bowl models with seven different flushometer valves, for a total of 49 different bowl/valve combinations. Included within the study were measurements of the variations in flush volume that could be achieved with adjustments of the flush valves or the control stop. This study was sponsored by the City of Toronto, and the Regions of Durham and Waterloo in Ontario, Canada.

van Gelder, R. (2003) Performance Testing of Wall Mount Siphon Jet Toilets - Seattle Public Utilities funded a comprehensive 2003 study of the flush performance of 28 flushometer toilets (8 different models) coupled with 34 manually operated flushometer valves (6 models), all of which were installed on the campus of the University of Washington. A battery of tests was run on each of the eight toilet models that included various combinations and amounts of test media consisting of toilet paper, seat protectors, tofu, and concentrated brine solution. Download a copy of the study report for further information, however, readers should be aware of the following caution from Seattle Public Utilities:

NOTE: This research is not intended as a selection guide for commercial toilets and flush valves. The site-specific performance requirements (weighting criteria) in the report are specific to the facility staff at the University of Washington. The author cautions readers not to directly apply the rankings or results of this research to other sites or locations without further testing. Under different circumstances and using different testing protocols and larger sample sizes, much different results, rankings, and conclusions could be obtained. Few research studies have attempted to document flushing performance outside the lab due to the many variables that exist. This paper documents variations in actual flushing performance between lab tests and functional installations. This research subsequently stimulated more realistic laboratory and field testing protocols for flushometer valve toilet fixtures. Download the study: 

NAHB Research Center Low-Flow Toilet Study (2002)  The National Association of Home Builders Research Center, in cooperation with Seattle Public Utilities and the East Bay Municipal Utility District of Oakland, CA, released the water closet fixture performance study that was underway for much of 2002. The report details the results of extensive performance testing (with sponges and paper wads) on 49 of the most popular low-flow toilets in the United States and Canada.

NOTE: The results of the NAHBRC testing are not meant to be a direct assessment of which toilets will or will not perform well in a home environment. Only two samples of each toilet model were tested, and the material used in the testing may not be an appropriate substitute for measuring "real-world" toilet performance. 

Recognizing that the use of sponges and paper wads might not accurately replicate "real-world" demands placed upon a toilet fixture, this study was followed by the development of the MaP testing protocol in 2003, sponsored by 22 water provider interests.

  - NAHBRC (2002) Water Closet Performance Testing – Final Report  

  - NAHBRC (2002) Toilet Performance Results Index  

  - NAHBRC (2002) Ranking and Comparing Consumer Reports and NAHBRC Research on Toilets  

Customer Satisfaction Survey (gravity-fed residential toilets) (1999) 

MWDSC (1999) ULFT Customer Satisfaction Survey - The Metropolitan Water District of Southern California commissioned Honeywell DMC to perform a survey of 1,300 individuals who installed new gravity-fed 1.6 gpf (6.0 Lpf) toilets in 1998 and 1999. A total of 13 different toilet models were rated by customers on a variety of important performance factors.

Long-term Durability of Toilet Fixtures (2001) 

MWDSC (2001) ULFT Long Term Durability Test - The Metropolitan Water District of Southern California undertook to test three new toilet models that had recently been introduced into the marketplace. Eight fixtures were each subjected to 250,000 flush cycles. Where potential problems appeared, manufacturers addressed those problems and improved products resulted.

Testing of Toilet Fixtures Against Proposed National Standards (2001) 

Koeller J. (2001) Laboratory Evaluation of ULF Toilets - Fifteen water providers in the U.S. sponsored a comprehensive toilet testing program at the Stevens Institute of Technology. Designed to evaluate the efficacy of a proposed new test protocol for the national standard, this year-long effort compared the performance of 18 different gravity-fed and pressure-assist toilet models.

Functioning of Aging ULF Toilets in Tucson AZ (2000) 

Henderson, J. and G. Woodard (2000) Functioning of Aging Low-Consumption Toilets - This study, sponsored by the City of Phoenix and the U.S. Bureau of Reclamation, is a "one-of-a-kind" project, because it is the first study to look at ULF toilet fixtures of 1991-92 vintage to see how they were performing after 8 years of use.  The University of Arizona Research Center data-logged 170 homes and analyzed the results for flush volume, double-flushing, leakage and other factors.  This was followed by household surveys to determine the types of installed toilet fixtures and owner satisfaction with those fixtures.

Toilet Flush Volume Study (2001) 

Veritec (2001) ULF Toilet Performance Monitoring Program - This comprehensive field study documents some very interesting characteristics of common gravity-fed toilet fixtures. In particular, ULF toilets operating at abnormally low flush volumes (well below their rated flush volume of 6 liters - 1.6-gallons) were field measured to determine just what was really happening inside the home. 

Flapper and Flush Valve Seals

Koeller, J. (2004) Toilet Flapper Study Final Report - This comprehensive field study of the durability of toilet flappers, and the habits and practices of homeowners with respect to flapper replacement and use of in-tank bowl cleaning tablets, involved the inspection of 892 randomly selected toilet fixtures in homes throughout California.  Products from 14 manufacturers with production dates from 1992 to 2002 were measured for flush volume and subjected to a flapper inspection.

Flapper Materials Durability Studies (1994-2000) 

These three laboratory studies by the Metropolitan Water District of Southern California were a catalyst in the plumbing industry’s advancements in flapper materials durability. As chlorine-based drop-in bowl cleaning tablets made their way into the consumer marketplace (and into their toilet tanks), flapper failure and toilet leakage became a significant concern of the plumbing industry and the water authorities.  Beginning in 1994 and working together, more durable products resulted.  Download all three study reports here:

Koeller J. (2008) Toilet Flappers - The Former Weak Link of Water Conservation - Why were toilet flappers getting so much attention from water conservation professionals and manufacturers in the 1990s?  Read about the evolution of the flapper problems through the 1990s until today.

After-Market Toilet Flappers: Compatibility and Flush Volumes (1998) 

This 1998 Metropolitan Water District study focused on the compatibility of flappers found in the traditional after-market (at Home Depot, Lowe’s, and hardware stores) with the typical gravity-fed toilet fixtures found in most residential households. A total of 50 aftermarket flappers were fitted to 24 different toilets. Flush volumes were measured and reported in this document:

After Market Flapper Study Report (PDF)

Flapper Replacement - Marketing Strategies Report (2004) 

Tampa Bay Water (2004) ULF Toilet Flapper Marketing and Implementations Strategies Program - Outreach and marketing strategies directed at encouraging customers to replace aging and leaking flappers is the subject of this final report. Tampa Bay Water, its participating member governments, and consultants developed a variety of methods and tools to aid customers. Download this report, read about those approaches, and access their large database of toilet fixtures and replacement flappers.

Toilet Retrofit Devices 

Learn about toilet retrofit devices here.