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Low-Flow Toilets

A low flow toilet stops flushing money down the drain
A low flow toilet stops flushing money down the drain

Trends and Technologies

On average, 26% of household water is flushed down the toilet, literally. This is a lot of water along with the energy required in treating before and after use. Here are some ways to reduce toilet water usage

  • Low flow toilets. Flush volume has been declining since the 1970’s due the improve construction of the flushing mechanism. Toilets that use 1.28 or less gallons per flush (gpf) are now available. Compared with the past products that use 3.6 gpf, this is a saving of 65% or more.
  • Dual flush toilets. This is an excellent idea that takes the low flow technology even further. The products offer both 1.6 gpf (for solids) and .9 gpf (for liquids) options in the same unit. In actual use, there are mixed reviews. Some users find these great. Others are disappointed that the low volume flush is not always effective enough, causing them to make a second flush. Check the product out carefully to ensure that it functions well.
  • Dual flush toilet actuation buttons
    Dual flush toilet actuation buttons
    Sink over toilet
    Sink over toilet
  • Choose products with the WaterSense label, which certifies that the product meets water saving performance according to EPA guidelines.
  • Use reclaimed water. It is clearly a waste of potable water to use it for flushing. Now there are products that collect and filter water from bathroom sinks. This water will be used first to refill a toilet tank. A recent product has a wash basin sitting ontop of the toilet tank so that the water you use to wash your hands immediately after a flush gets put back into the tank. Stored rainwater is another source for flushing water.


Studies have quantified water savings with using efficient toilets. The summary is tabulated below.

Homes with Inefficient Toilets Homes with Low Flow Toilets Difference
Flush Volume Per Flush (gallons) 3.61 * 1.28
Flushes Per Capita Per Day 5.17 * 5.46 * 0.29
Flush Volume Per Capita Per Day (gallons) 18.8 * 7.0 -11.8
Flush Volume Per Capita Per Year (gallons) 6862 * 2555 -4307
* Source: DeOreo, et. al. 2001

To translate the table data into monetary savings, let’s use an example. Water is typically sold in units of 100 cubic feet (=748 gallons). Assume water costs $3 a unit (which is typical in California), a family of four can save

$3 (/unit) x 4 (persons) x 4307 (gal/person) / 748 (gal/unit) = $69

per year by changing to low flow toilets.

Costs, Rebates and Incentives

Low flow toilets are installed the same way as older toilets so there is no additional installation cost. Depending on the models low flow toilets can start at as little as $100, and are no more costly than older models.

Some water providers, cities, and utility companies offer financial incentives for replacing old inefficient toilets. Typically they offer a rebate of between $25 and $100 per toilet. In some cases they may offer free toilet replacement.

For information about toilet rebates and incentive programs in your area, contact your local water provider.

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