When you are installing a water heater, you need to include a backflow preventer into the pipes. This will prevent water from flowing backwards, and contaminating drinking water. It stops water that has been heated rejoining your water supply because this can also affect the pressure in your water heater. When you are fitting the backflow preventer, you should pay attention to some simple rules.
Fit Before the Heater
You need to fit the backflow preventer onto the pipes before they reach the heater. Make sure that the pipes don't go upwards in an incline before they reach your preventer. Check that it is securing all of the water inlet pipes. You should fit the backflow preventer a short distance from the heater, so that it is not affected by the warmth of the heated water. Don't place the backflow preventer between a heater and an expansion tank.
Always check that you are fitting your backflow preventer in the correct position. This is more complex than it looks. An incorrect fitting will allow water to flow back down the pipe, but will inhibit the flow of water to your tank. This could result in an increase in pressure which will severely damage your tank.