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Launch Slideshow

High-Efficiency Toilets

High-Efficiency Toilets

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    American Standard (left)

    Traditional, wash-down and power-flush toilets (left to right)

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    The WaterSense label was created to make it easier to find and choose waterefficient plumbing products. Labelled toilets have undergone third-party testing showing that they can clear at least 350 grams of solids from the bowl while using no more than 1.28 gallons per flush.

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    Most of the toilets sold in this country rely on siphoning action to pull waste into the drain. The siphon is initiated by a jet in the bottom of the bowl, which uses a portion of the flush water to push waste over the high point of the trap. The remaining water comes out from the rim and refills the bowl.

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    Washdown toilets send the entire flush to the rim, flooding the bowl from above and pushing waste out through the trap.

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    A power-flush model is equipped with a vessel that contains water and compressed air. The air propels the water into the bowl at high velocity, producing a flush that is both powerful and loud.

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    Siphoning toilets tend to stay clean because the water spot — the area of the water inside the bowl — is large enough to keep solids away from the porcelain.

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    A wash-down model typically requires frequent brushing because its water spot is too small to keep solids off the bowl.

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    Toto's double cyclone models contain a pair of jets under the rim that the maker says are particularly effective at scouring the bowl.

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    Caroma

    Dual-flush toilets like this Caroma use a full flush for solids and a half flush for liquid.

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    Caroma

    Instead of a standard lever, the fixture has a dual-flush button on top of the tank.

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    In preparation for a MaP test, soybean paste is extruded into 3/4-inch-diameter cylinders.

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    Testing is performed by dropping a predetermined mass of cylinders into the toilet, adding tissue, and then flushing. The process is repeated with successively larger amounts of soybean paste until flushing no longer clears the bowl.

Field-Tested Favorites

We try to steer clients toward toilets we know they’ll be satisfied with. To find out which models work best, we field-tested a series of toilets by installing them in our office bathroom. After a couple of months of use, we compared notes on the performance of each model before replacing it with another.

We’ve tested six different toilets in the past year, all but one of which were early-release HETs from manufacturers with wide distribution in our area. All had MaP scores between 550 and 1,000 grams. Despite the range in scores, we were unable to discern any difference in their ability to clear solids — they all did a consistently great job.

However, we found notable differences in backwash, cleanliness, and noise. Our staff gave a thumbs-down to the Kohler, American Standard, and Caroma models for various combinations of these attributes. The Kohler Wellworth Pressure Lite toilet, for instance, was explosively loud and had frequent occurrences of dirty water remaining in the bowl. The American Standard FloWise fixture suffered from backwash and required constant porcelain brushing. And the Caroma, with its dual-flush action, was confusing for some to use and had pronounced problems with backwash and soiled porcelain.

After a year of testing, we decided we liked Toto’s Eco (E-Max) series best. It’s quiet, clears the bowl of solids, leaves clear water after the flush, and rarely requires brushing. We generally recommend it to our clients, and — because there are several models in the Eco E-Max series to choose from — they can usually find a style they like.

Drain Transport

When 1.6-gpf toilets first came out, there was some concern that they would not provide enough water to deliver waste to the sewer. But experience has shown that this is rarely a problem in residential construction, where horizontal drain runs are short. If the initial flush doesn’t push the waste all the way to its destination, water from the tub, shower, and washing machine will soon purge the line.

But problems can develop when the toilet is connected to a long horizontal waste run and there are no high-volume fixtures nearby. An example would be a commercial half-bath on a concrete slab in a warehouse. We once did service work for a client who had a 1.6-gpf toilet in a half-bath with an 80-foot horizontal drain line that likely didn’t slope enough. The only way to keep it from clogging was to purge it occasionally by pouring buckets of water down the toilet — hardly an ideal solution.

In new installations, I encourage the architect to locate bathrooms as near to a sewer outfall as possible, or on a lateral that contains other fixtures that will purge the line. As long as there is 1/4 inch per foot of slope, the line will usually clear satisfactorily. Because the initial wave of flush water carries farther in a smaller pipe, we like to use 3-inch (rather than 4-inch) drainpipe when we’re concerned about the length of the horizontal run — but only after making sure that the option is permitted by the local code.

Leigh Marymor co-owns The Lunt Marymor Co. in Emeryville, Calif., with Jim Lunt.


How Toilets Are Tested

Toilets sold in the U.S. must comply with performance standards developed by the American Society of Mechanical Engineers in conjunction with manufacturers. The ASME standards, however, have barely been heard of outside of the plumbing industry. Far better known is a voluntary performance standard based on MaP (Maximum Performance) testing, which was developed at the behest of the Canadian Water and Wastewater Association (CWWA) and a consortium of U.S. and Canadian utilities.

The beauty of the MaP test is that it provides a realistic measurement of the single most important aspect of performance: the ability to completely remove solids in a single flush. Under the ASME standard, toilets are tested by flushing sponges, paper, nylon granules, and nylon balls. In the MaP test they flush toilet paper and tubular pieces of soybean paste (miso), which — to put it delicately — look and behave like the real thing.

The MaP test is performed by dropping miso and a specified number of sheets of toilet paper into the bowl and then flushing. Miso is added in increments of 50 or 100 grams with testing performed until either the bowl won’t clear or 1,000 grams (2.2 pounds) is reached. Each toilet model is rated on its ability to clear the bowl of solids with a single flush. Units that fail to meet the minimum 350-gram criteria do not receive a rating.

When testing began in 2003, the threshold requirement was 250 grams, which according to a British medical study is the “maximum average fecal size” of the males in that study. For the sake of consistency, the MaP standard was revised upward when the EPA adopted a 350-gram standard for the WaterSense program.

MaP testing is performed on an ongoing basis, and the results are reported every four to six months. The latest edition of the report came out in October 2009 and contains MaP scores for more than 2,000 different toilet models. It can be accessed from a variety of Web sites, including that of the testing company — Veritec Consulting (veritec.ca) — and the California Urban Water Conservation Council (cuwcc.org). —

David Frane