Buying a Water-Efficient Toilet: Additional Considerations

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  • Author John Carle
  • Published December 3, 2011
  • Word count 1,079

There are a number of additional considerations besides flushing performance that you should think about when buying a toilet. These include the following:

Rough-in Dimension

The vast majority of North American homes have a rough-in dimension (the distance from the wall behind the toilet to the centre of the floor flange) of 305 mm (12 in.). However, you should measure your rough-in distance before you buy to ensure your new toilet will fit the existing space.

One-Piece vs. Two-Piece

One-piece toilets (where the tank and bowl are purchased as a single unit) can be easier to clean and may have less opportunity to leak at the junction between the tank and bowl than two-piece models. However, one-piece toilets can also be more expensive, as well as heavier and harder to install.

Bowl Height

Toilet bowls generally come in one of two heights: regular or "comfort-height." Comfort-height bowls are slightly higher than regular bowls, which many people find makes them more comfortable to use. If you are tall, have bad knees or have a disability, you may want to consider a comfort-height bowl. Toilet bowls qualified by the Americans with Disabilities Act (ADA), for example, must measure between 430 and 480 mm (17 and 19 in.) from the finished floor to the top of the seat.

Bowl Shape

Up until a few years ago, almost all residential toilets had round bowls with doughnut-shaped toilet seats. Toilets in office buildings, airports and other commercial spaces, on the other hand, tended to have egg-shaped or elongated bowls. Today, many homeowners are opting to install elongated bowls in their homes. The choice is primarily a matter of personal preference, though toilets with elongated bowls may not fit easily in some smaller bathrooms.

Single- or Dual-Flush

Dual-flush toilets were originally introduced to help conserve water. But with the development of single-flush models that use only 4.8 L of water or less, the comparative water savings of dual-flush toilets has eroded somewhat. The choice between single- and dual-flush toilets is now related more to personal consumer preference than to any real water savings.

Flushing Performance

Toilet models with the highest MaP performance scores can flush between 800 – 1,000 g of waste. But for most consumers, any toilet model (preferably WaterSense-approved) with a MaP score of 350 g or more will likely meet or exceed their flushing performance needs.

Gravity or Pressure-Assisted

Most residential toilets work by means of simple gravity — water is stored in the tank at a higher level than the water in the bowl. When the toilet is flushed, water flows by gravity from the tank to the bowl. Water is then pulled from the bowl into the drain by a siphon effect, then down the drain to the sewer. With pressure-assisted models, the water is stored in a canister inside the toilet tank, where it is kept at the same pressure as the water that is supplied to the toilet. When the toilet is flushed, the pressurized water forces a power flush action through the bowl. Up until 2003, pressure-assisted models generally offered better performance than gravity models. Today, however, gravity and pressure-assisted toilets both offer relatively equal flushing power, making the choice between them more a matter of personal preference than performance.

Flapper Size

Flappers (or flush valves) on nearly all North American toilets are either 50 mm (2 in.) or 75 mm (3 in.) in diameter. Generally speaking, a 75-mm (3-in.) flapper will allow water to discharge from the tank to the bowl much faster, resulting in better performance. While a75-mm (3-in.) flapper is not a guarantee of more flushing power, nearly all high-performance toilets produced by major manufacturers are now equipped with a flapper of that size.

Trap Diameter (Siphonic vs. Washdown)

Until recently, virtually all residential toilets in North America were siphonic, meaning they used the natural siphon created by the flushing water in the toilet trap to "pull" waste from the bowl. The smaller the toilet trap, the easier it is to create the necessary suction. But smaller traps can also make it more difficult for the waste to pass through. Washdown toilets, on the other hand, use the water entering the bowl to help "push" the waste through the trap. Because they don’t need to rely only on a siphon, washdown toilets can have a considerably larger trap diameter. But, because of the way they work, they also tend to have a much smaller water surface area in the toilet bowl. As a result, washdown toilets generally tend to clog less often than siphonic toilets, but they may also require more frequent cleaning.

Drainline Carry

Despite some early concerns, extensive testing has shown that water-efficient toilets provide more than enough water to transport waste through your home’s drainpipes to the sewer. If you find your toilet is frequently plugged, it is more likely a sign that your drainpipes are partially or fully blocked than your toilet is not functioning properly.

Lined vs. Unlined Tank

Toilets come with lined (insulated) or unlined tanks. The lining helps prevent the condensation, or "sweating," that can form on the outside of the tank during hot, humid summer months due to the presence of cold water in the tank. A lined tank may not be necessary if your home is air-conditioned, your indoor air is relatively dry and your municipal or well water is not too cold. If unsure, consult with a local toilet installer or retailer to find out what is recommended for your area.

Supplementary Purchase Specification (SPS)

Another performance criterion that can be used to identify high performance toilets is the Supplementary Purchase Specification (SPS), created by the Los Angeles Department of Water and Power to measure the performance and durability of toilets over the long term. To meet the SPS standards, a toilet must have chemically resistant trim components that won’t be damaged from exposure to chlorine. It must also have a pilot fill valve (or equivalent) to ensure that the water level in the tank remains at the proper level over time, regardless of changes in the water pressure. Furthermore, it must not permit any adjustment that would allow the toilet to flush with more than 7.6 L of water. To find out if a toilet meets the SPS requirements, look up its name and model in the MaP report tables, or purchase a WaterSense-certified toilet, which guarantees the same stringent requirements.

With these considerations in mind, you should be ready and able to choose a toilet that’s right for your home, your pocketbook — and the environment.

John Carle

RE/MAX Real Estate Edmonton

102 12650 151 Ave

Edmonton, AB T5X 0A1

780-937-7534 / 780-701-9090

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