If you use plastic bottles or bags, they must be weighted and filled with water before installed. 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. Faucet Most faucets have aerators that mix water and air, resulting in a capacity of about four gallons per minute. Low-volume faucet aerators mix water and air and cut consumption in half. These devices are easy to install. All that is required is to remove the old aerator and replace it with the new low-volume aerator.