If bricks are used, wrap in a plastic bag to prevent decomposition. The average family of four could save about 10 gallons of water per day through the installation of these displacement devices. Generally, devices such as these are installed in pairs, one dam on each side of the flapper valve. Properly installed, the dams reduce water consumption by about two gallons per flush. A family of four could save about 25 gallons of water per day through installation of toilet dams.
Most commodes require about five gallons of water per flush.
Today, many major plumbing appliance manufacturers are marketing low-volume commodes that use three gallons of water per flush. These devices are easy to install. This reduces to about three gallons per minute the flow of water through the pipe. Devices such as these may be as simple as a washer or they may be more complex. The cost may vary from 50 cents to several dollars.