Results to your Question Search:
Should i install a backflow preventer on a water heater?
[Donate an Answer to this Question]
What is backflow or backsiphonage?
Am I legally required to have a back flow prevention device?
When a new water heater is installed a backflow preventer needs to be installed into the water pipes. This will prevent water from flowing backwards, and contaminating drinking water. It stops water that has been heated from rejoining your water supply as this temperature change can also affect the pressure in your water-heater.
It is always best to leave this installation to a
licenced professional like the pros at www.delandplumber.com
Your professional will fit the backflow preventer onto the water pipes before they reach the heater. The pipes should not go upwards in an incline before they reach your preventer. The backflow preventer should be only 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. 
Web Reference: none