What is a Dual Flush Toilet?

N. Swensson

A dual flush toilet is designed to conserve water by using less water for flushing liquid waste than solid. Most models have two buttons, one for a liquid waste flush and another for solid waste. In addition to its water-saving benefits, dual flush toilets may clog less frequently than conventional models. One drawback, however, is that they don't always completely remove solid waste from the bowl, and may need to be cleaned more often. This type of toilet is more popular in Australia, Europe and Asia than in the United States.

Dual flush toilets are designed to conserve water by using less of it to flush liquid waste.
Dual flush toilets are designed to conserve water by using less of it to flush liquid waste.

Water conservation is the main benefit of a dual flush toilet. A conventional toilet can use as much as 5 gallons (19 liters) of water for every flush, while a dual flush toilet can use less than 1 gallon (3 liters) to flush liquid waste and about 1.6 gallons (6 liters) for solid waste. Dual flush toilets also have a larger tube where waste exits, making clogs less frequent.

A toilet is a plumbing receptacle for human waste.
A toilet is a plumbing receptacle for human waste.

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A conventional toilet uses a siphoning mechanism to draw a large quantity of water and waste down and out of the bowl. When the bowl is empty, the siphoning action stops, and the toilet is refilled with a fresh supply of water. On the other hand, a dual flush toilet bowl is not full of water; it is mostly empty until it is flushed. Then, water washes down the bowl and pushes waste out through the drain. The disadvantage of this is that more waste may remain on the sides of the toilet bowl, and more frequent cleaning may be necessary. Despite these drawbacks, the rising cost of water and an increased interest in environmentally responsible construction are making dual flush toilets a more popular option, especially for new construction.

A dual flush conversion kit is one option for homeowners who want to benefit from the water savings of a dual flush model but are not ready to replace their existing toilets. The kit will install a similar push-button mechanism so that a lower flush can be selected for liquid waste, but the toilet still works the same way. Conversion kits can also be more affordable — they can be purchased from home improvement stores for as little as $18 US dollars. A new dual flush toilet, on the other hand, can cost anywhere from $100 to $900 US dollars.

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