Check valve for water inlet on hot water heater ?

[Ed]

Should I put a back flow preventer or check valve on the water inlet on a water heater ?

[Toller]

Thats about the last thing you want to do. Why would you even consider it?

[Charles Schuler]

That depends. A house that I owned up until 6 years ago was on top of a hill. When the water supply failed (e.g. when there was a fire on my circuit and the pumpers went whole hog) the water from the tank got sucked back into the mains and the heating elements on my heater burned out ... happened several times ... I was forced to install a check valve.

[Toller]

I am tempted to say that is impossible. Even if a siphon could be established, if no taps are open the water in the heater couldn't get sucked out.

[Bob M.]

As the others have asked, why? Siphoning the water tank dry sounds pretty unlikely if all taps are closed.

But anyhow, your water meter may already have one as I believe most newer meters are required to have them (

[DerbyDad03]

There are (at least) 2 possible reasons for a check valve on the inlet of a hot water heater.

1 - Some municipalities require a check valve to prevent the flow of water from the house back to main. 2 - A check valve is used when a recurculating system is used to prevent long waits for hot water at fixtures far from the heater.

If you do use a check valve, you should also use an expansi> Thats about the last thing you want to do. Why would you even consider it?

[DerbyDad03]

- I am tempted to say that is impossible. Even if a siphon could be

- established, if no taps are open the water in the heater couldn't get sucked

- out.

I'd like to agree, but this thread seems to indicate that its possible:

Read the last response in the thread.

[gfretwell]

That is strange. They require "backflow preventers" (2 check valves) on every water service around here. You might be able to contaminate your own water lines but your water will never get back to the street.

[Ed]

My water comes from my artesian well. I am concerned about losing heated water flowing back towards the well tank.

Thanks

Ed

[buffalobill]

[Edwin Pawlowski]

In most cases, no. but some towns are now requireing backflow preventors in every home. They are needed with in-ground sprinkler systems.

[Harry K]

If it is required by code, it will be required at the house supply inlet, usually where the service enters the house (unless it is part of the meter). It won't specify that it is neededon the water heater. Someone else pointed this out but I will add it again. If a check valve is placed on the heater inlet, then an expansion tank should be installed.

Harry K

[Mike]

replying to Toller, Mike wrote: It?s called a vacuum breaker bud. Let?s air into the tank to prevent it from imploding in backflow conditions.

[Hunter]

replying to Ed, Hunter wrote: If your cold water comes into the water heater from the bottom, as it does in a mobile home, the water will definitely siphon out causing your elements to burn out.

[Rudy]

replying to Hunter, Rudy wrote: The solution is to install a syphon breaker valve. Run the supply line up above the top of the tank and place the syphon breaker there. Tee off just below the syphon breaker and run pipe to the water heater inlet. If there is any syphon on the water line, the valve will open and let air in, breaking the syphon. Because the valve is above the tank, the water in the tank is trapped. This is code where I am. If you use a check valve, it has to be a two way check valve with a relief port to allow expansion to escape back into the water line when the water is heated.