Low flush toilets, which have been the standard since 1994, use 1.6 gallons of water for each flush while older models use between 3.5 and 7 gallons per flush. If you want to save even more water, WaterSense-labeled high-efficiency toilets use 1.28 gallons of water or less per flush. An average household could save up to 2,400 gallons of water per month just by replacing a 1950s-era toilet with a high efficiency toilet. Even toilets that use 1.6 gallons per flush provide water and sewer bill savings that pay for the cost of replacing a toilet in three years or less.

If you are not ready to replace your toilet, you can reduce water used per flush by installing an object that displaces water in the toilet tank. A plastic bottle weighted with water or gravel works well, but don't use bricks and old milk cartons. These deteriorate and can reduce the effectiveness of your toilet’s valves or its overall function. Make certain that the displacement device does not block any moving part inside the toilet tank or you could cause your toilet to run and waste water.

A silent toilet leak, often caused by a flapper that does not close completely, can waste 50-500 gallons of water per day. A silent toilet leak that wastes 250 gallons of water a day would cost a city of Tacoma resident over $40/month in water and sewer charges. To check for toilet leaks, take the lid off the tank during a flush and watch what happens. The water should come up to the mark impressed into the ceramic of the tank. If necessary, bend the arm of the float arm down so that the re-fill valve shuts off at that water level. If the re-fill valve itself is leaking, you may want to work with a plumber.

Now, drop a little food coloring in the tank and see if it comes out of the bowl without flushing. If color appears, you probably have a leak at the flapper valve on the bottom of the tank. Flapper leaks can be caused by a worn flapper (easily replaced) or by a corroded flapper valve seat, which needs to be replaced by a plumber.