Prior to 1992, the average toilet in the U.S. used at least 3.5 gallons of water per flush (GPF). In 1992, the federal government passed a new standard for toilet manufacturers aimed at conserving water. All toilets installed after 1992 may use no more than 1.6 GPF, and many consumers choose advanced models that use 1.0 GPF or even less. While the EPA estimates that low-flow toilets save families $90 a year on water bills, the most important benefit of these toilets is that they help conserve the world's limited water supply. Unfortunately, early low-flow toilets were problematic, and even new models don't offer the same performance as higher-flow toilets.
According to the Santa Cruz County government, low-flow toilets cost about $100 more than standard-flow models. Those with a dual-flush option, which give users the chance to choose the amount of water based on the type of waste, can cost even more. While annual water savings can help to offset these extra costs, many consumers hesitate to buy low-flow toilets due to higher price tags.
While a dual-flush toilet works just like a standard gravity-fed model, many low-flow units use a pressure-assist technology. This means that an air chamber inside the toilet tank works with a small amount of water to force waste down the drain. These pressure-assist toilets make a distinctive "whooshing" sound that tends to be louder than a regular flush. This can be particularly problematic in apartment buildings and homes with shared walls.
Most of our existing water and sewer pipes were sized to work with toilets that use 3.5 GPF or more. In some cases, low-flow toilets may not have the power to flush waste far enough into the pipes to keep them flowing properly, which can lead to clogs. Even if the pipes are kept clog-free, some sediment may be left behind that can corrode metal pipes over time. Sewer systems that are already in need of repair will be made even worse if a low-flow toilet is installed without first fixing the pipes.
According to the EPA, this problem occurs less often with newer low-flow toilets than it did with earlier models.
According to Santa Cruz County, gravity-fed, dual-flush toilets require 10 to 15 psi of water pressure, while pressure-assist models need 25 to 40 psi. Some homes may not have sufficient pressure to operate these toilets, so buyers should always consult a plumber first before buying a low-flow toilet. If pressure is too low, the toilet will not operate as intended, which could lead to clogs or the inability to flush at all.
One of the most common complaints with a low-flow toilet is that not all waste is transported in a single flush. Some larger quantities of waste may require two or more flushes, which quickly negates the impact of the low GPF rating. With liquid waste, a low-flow toilet tends to drain easily using only a single flush.