A low-flow toilet is a flush toilet that uses significantly less water than a full-flush toilet. Low-flow toilets use 6 liters (1.6 gallons) or less per flush as opposed to 13.2 liters (about 3.5 gallons) as was the norm years ago. They came into use in the United States in the 1990s, citing water conservation concerns. Low-flow toilets include single-flush models and dual-flush toilets, which typically use 1.6 gpf (gallon per flush) for the full flush and 1.1 gpf for a reduced 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. In addition to tank-type toilets that "pull" waste down, there are also now pressure-assist models, which use water pressure to effectively "push" waste.

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.

Many people disliked the low-flow toilets because they had to flush the toilets twice to achieve their desired task. The performance of some low flow toilets has significantly improved since 1994.

In 2011, the San Francisco Chronicle reported that, while low-flow toilets are estimated to have saved the city of San Francisco 20 million gallons of water per year, the reduction in water volume has caused waste sludge to back up in the city sewer pipes. The city is attempting to solve this by adding chlorine bleach to the pipes, a proposal that has raised environmental objections.

A dual-flush toilet is a variation of the flush toilet that uses two buttons or handles to flush different levels of water. Although the first generation dual-flush toilet caught on, a redesign in 1993 cut water usage in half when used properly. It has been proven to save up to 67% of water usage in most homes. Due to the more complex mechanism, it is more expensive than many other types of low-flow toilets.

See also:
Low Flush Toilet
Dual Flush Toilet

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