Low Flush Toilet

Low Flush Toilet

A low-flush toilet or low-flow toilet is a flush toilet that uses significantly less water than a full-flush toilet. Most low-flush toilets use 6 liters (1.6 gallons) per flush as opposed to the usual 13.2 liters (about 3.5 gallons). They came into use in the United States in the 1990s, citing water conservation concerns. Many dual flush toilets have a 6 litre and a lower flush.

In 1992 President George H. W. Bush signed the Energy Policy Act. This law made 1.6 gallons per flush toilets standard. This law went into effect in Jan 1, 1994 for residential buildings and Jan 1, 1997 for commercial building where it cannot consume more than 1.6 gallons per flush.

The first generation of low-flow toilets were designed like traditional toilets. A valve would open and the water would passively flow into the bowl. The resulting water pressure was often inadequate to carry away waste. Current models use water pressure to charge a pressure vessel with air to propel the lesser amount of water into the bowl in a shorter period of time.

The Mendelsohn House apartment complex in San Francisco replaced every 3.5 gallon traditional toilet in their 189 apartment units with 1.0 gallon high efficiency toilets equipped with Sloan Flushmate IV pressure vessels. This single apartment complex saved four million gallons of water per year.

The US Environmental Protection Agency's WaterSense program provides certification that toilets meet the goal of using less than 1.6 gallons per flush. Units that meet or exceed this standard can carry the WaterSense sticker. The EPA estimates that the average US home will save $90 per year, and $2,000 over the lifetime of the toilets.