Plumbing Info

When 1.6 toilets were introduced, there was resistance to limit the water closets only to residences. Here’s the news story on what the ASPE Research Foundation found.

courtesy of Plumbing & Mechanical Magazine, August 1992
by Jim Olsztynski

1. 6 Water Closets Questioned For Commercial Applications

Ultra-low flush water closets should be limited to residential applications until design improvements can produce a fixture capable of consistently handling the demands of commercial applications, according to the ASPE Research Foundation.

The Foundation’s recommendations are based on a 9-page report that details a 30-month study that involved laboratory testing of 14 commercial, ANSI-approved 1.6 gpf closets (with a control group of 12.35 gpf units), and analysis of actual commercial installations from New Jersey to California.

Field testing of the commercial wall-hung 1.6 unit revealed marginal performance. Clogging of the bowl’s trapways occurred more frequently than with the wall-hung 3.5 closets in the control group. In general, in commercial applications where the fixture may be used to flush more than body wastes and the normal amount of toilet tissue, the existing 1.6 units do not provide the same level of service.

Overall Performance: In laboratory testing, the performance of 1.6 water closets is not appreciably different from conventional 3.5 units as measured by the ANSI test protocol. In a supplemental mixed media test performance is significantly different. (ANSI is evaluating the test used in the ASPE Research Foundation’s study.)

Results showed that gravity-operated 1.6 water closets received lower scores on the mixed media evacuation test which indicates a greater tendency for choking or clogging at the entrance trapway. Pressurized tank unit test results were comparable to 3.5 gpf water closets. In transport studies both types of 1.6 gpf models performed at significantly lower levels than the conventional water closet, though gravity tanks outperformed the pressurized units. All products tested passed the ANSI drain line carry test.

In field studies, flush volumes for the 1.6 gpf closets ranged from 1.34 to 2.44 gpf, with an average volume of 1.8 gpf. Double flushing occurs at a grater rate with the low flow units. The average number of flushed per day per person increased 16%. Despite this flushing increase, residential water savings from low flow fixtures was 5.3 gallons per person per day.

Cautions: Based on the study, the Foundation Board concluded:

1) The relationship between the water closet and drain line is more critical at reduced flush volumes. There fore, in very long drain lines where few fixtures contribute to the flow, low-flow water closets may lead to transport problems and drain line blockages. In addition, when the condition of the drain lines is questionable (sagging, reverse pitch, etc.), the use of 1.6 water closets may lead to stopages.

2) In the interest of maximizing water savings without sacrificing performance, dual-flush water closets — units that use different volumes of water to flush liquid and solid waste — should be investigated.

Commenting on the new report, Foundation president Albert Collado said, “… There is every reason to believe that as our experience with these units increases and as we learn more about the physics of fixture evacuation and drain line carry, we — the plumbing industry — will be able to produce a fixture that will give comparable performance to the 3.5 gpf unit at reduced volumes.”

In a related development, an updated version of the Plumbing Products efficiency Act was attached as an amendment to the National Energy Policy Act that passed the House by a 381-37 margin. Introduced at the eleventh hour, the amendment was sponsored by Rep. Chet Atkins (D-MA), the original author of the Plumbing Products Efficiency Act.

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