High efficiency toilets
By Susan Ecker, Rumsey Engineers
Drought is becoming a major issue, both in this country and around the world. Although much attention is given to oil, water is vital to sustain life and, therefore, its importance should not be minimized. A recent government survey showed that at least 36 states are anticipating local, regional or statewide water shortages by 2013. But by using water more efficiently, we can help preserve water supplies for future generations, save money and protect the environment.
Currently, in the San Francisco Bay area, due to shrinking reserves, some water utilities are mandating a 10 percent decrease in water consumption by homeowners. In order to accomplish this, conservation practices are being implemented. Homeowners may be decreasing their time in the shower, curtailing or eliminating landscape irrigation and/or installing new water conserving plumbing fixtures.
One of these fixtures is the toilet. If you recall, when the 1.6 gallon per flush (gpf) toilet was introduced in this country, it was not welcomed with open arms. Many times it took multiple flushes to clear the bowl, making users wonder whether water was really being saved. Today, there are high efficiency toilets, or HETs, as they are commonly referred to. These toilets are tested by an independent testing agency and cataloged according to the weight of material that can clear the bowl in a single flush.
High efficiency toilet fixtures
Two types of toilet fixtures dominate the marketplace: Ultra-Low Flush Toilets (ULFTs), aka "low flow" or "ultra low flow," and HETs. ULFTs are defined by a flush volume in the range between 1.28 gpf and 1.6 gpf.
The HET is defined as a fixture that flushes at 20 percent below the 1.6 gpf maximum or less, equating to a maximum of 1.28 gpf. The HET category includes dual flush fixtures.
This 20 percent reduction threshold serves as a metric for water authorities and municipalities designing more aggressive toilet replacement programs 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 United States.1
Currently, this standard applies to tank type toilets only. Flushometer valve toilets have not been studied in the same way as tank types. Testing for flushometer valves needs to be performed on the flushometer valve with the various bowls on the market; the pair would then be rated.
WaterSense program
The EPA Energy Star program is easily recognized by the consumer as a way to save energy. Many consumers refer to this rating when they purchase a major appliance for their homes or businesses. Energy Star products use 10 to 15 percent less energy and water compared to standard models. The EPA wants to impact water conservation in the same way, so the WaterSense program was developed.
The specification for the WaterSense program is based on the Uniform North American Requirements (UNAR) for toilets and on industry and product research, in collaboration with external stakeholders. UNARs were developed by a collaboration of water utilities to establish a standard for toilets that would perform to customer expectations, save water and maintain water savings over the long term. The EPA specifications set the water use level at 1.28 gpf or less, include design requirements and, to ensure user satisfaction, have a higher requirement for flush performance.
UNAR establishes the criteria for a tank-type HET under the WaterSense program. It is applicable to the following:
- Single flush, tank-type gravity toilets
- Dual flush, tank-type gravity toilets
- Dual flush, tank-type flushometer tank (pressure-assist) toilets
- Tank-type, flushometer tank (pressure-assist) toilets
- Tank-type electrohydraulic toilets
- Any other technologies that meet these performance specifications
Power assist toilets operate using a pump to force water down at a higher velocity than gravity toilets do. These toilets require a 120V power source to operate the small, fractional horsepower pump. Typical flush volumes are between 1 and 1.3 gpf. Single and dual-flush models are available.
To be listed as a WaterSense toilet, the toilet must meet the following criteria.
1. Effective flush volume. Effective flush volume shall not exceed 1.28 gallons for both single flush and dual flush toilets. For single flush toilets, the effective flush volume is the average flush volume when tested in accordance with ASME A112.19.2, Vitreous China Plumbing Fixtures and Hydraulic Requirements for Water Closets and Urinals. For dual flush toilets, the effective flush volume is defined as the average flush volume of two reduced flushes and one full flush. Flush volumes will be tested in accordance with ASME A112.19.2 and ASME A112.19.14, Six-Liter Water Closets Equipped with a Dual Flushing Device.
2. Solid waste removal. Solid waste removal must be 350 grams or greater. Fixtures get a Pass or Fail grade based on whether the fixture can completely clear all test media in a single flush in at least four of five attempts. Toilets that pass qualify for the EPA WaterSense label.
Test media consists of seven test specimens, 50 +/- 4 grams each, consisting of soybean paste forming a "sausage" approximately 4 +/- 0.5 inch in length and 1 +/- 0.25 inch in diameter and four loosely crumbled balls of toilet paper. The flush performance criteria apply to single flush toilets and to the full flush option of dual flush toilets. The solid waste removal requirement does not apply to the reduced flush option on dual flush toilets.
There is a performance requirement associated with this program. A collaboration of U.S. and Canadian water utilities have developed a flush performance test protocol called the Maximum Performance (MaP) Test to provide a uniform measure of toilet performance. MaP test scores range from 250 to 1,000 grams. Products will be independently certified by a third party to confirm that the product meets EPA criteria for efficiency and performance. For a listing of toilets and their MaP test score visit www.cuwcc.org/MaPTesting.aspx.
3. Adjustability and other supplementary requirements. All single flush toilets must conform to ASME A112.19.2 and all dual flush toilets must conform to ASME A112.19.14. The criteria in this section apply to tank-type gravity toilets; these toilets must conform to ASME A112.19.5, Trim for Water-Closet Bowls, Tanks, and Urinals. The fill valve shall be the pilot valve type only or shall meet the performance requirements of the fill valve test protocol detailed on the WaterSense Web site. All fill valves must conform to ANSI/ASSE 1002.
The tank capacity, as defined by the EPA, is a barrier, bucket, dam, displacement device, or similar fixture used in a toilet tank to affect flush volume: the device shall be tamper-resistant and permanently affixed to the tank. Any device that can be tampered with or removed, such that the toilet can be made to flush with greater than the maximum flush volumes noted above, is non-compliant.
The maximum volume of water that may be discharged by the toilet, when field adjustment of the tank trim is set at its maximum water use setting, shall not exceed the following amounts:
- For single flush fixtures: 1.68 gpf
- For dual flush fixtures: 1.40 gpf in reduced flush mode and 2.00 gpf in full flush mode
The maximum volume of water discharged, using both original equipment tank trim and using after market closure seals, shall be tested according to the protocol detailed on the WaterSense Web site.
Drainline carry
Since the introduction of the 1.6 gpf toilet in the early 1990s, questions have been raised about whether sufficient water exists to move solid wastes in building drainlines and in municipal sewer systems. To date, there has been no evidence to show that waste transport problems occur because of the use of the original low-flow toilets.
The introduction of high efficiency toilets in the late 1990s precipitated the same concerns. As a result, a collaboration of water utilities sponsored a full laboratory study to address the issue. The drainline study, completed in 2004, concluded that HETs flushing with as little as one gallon provide sufficient water in residential and commercial applications to move the waste from the fixtures to the sewer.
With regard to municipal sewer lines, the transport of waste has not proven to be an issue of concern in those areas with a concentration of HETs. Supplementary wastewater flows from other end uses are always sufficient to move solids through the system. Furthermore, some wastewater utilities are co-funding and sponsoring the toilet replacement programs and other water efficiency initiatives of the water utilities for the very purpose of reducing sewer flows to their treatment plants.1
Conclusion
Many toilet fixture performance tests exist, including proprietary tests by the fixture manufacturers, tests by Consumer Reports magazine and the tests mandated by the plumbing codes for fixture certification. Few of these, however, use test media that closely resembles the real "demands" upon a toilet, i.e., that of removing human waste.
When choosing a high efficiency toilet, the plumbing engineer can choose a toilet based on performance, using the data provided by a third party testing company in the form of a MaP test score and the WaterSense label. Using independent third party testing based on measurable criteria makes the decision based an informed one. This is especially important when specifying low flow toilets, which were not well received when they were first introduced in this country, because they did not operate well.
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