PRV needed with expansion tank?

[ugabulldog]

I have an expansion tank between bladerless tank and house. Do I also need a pressure relief valve between well and tank? If so, does it matter if I put it at well head or on top of bladerless pressure tank?

 

[Valveman]

If you have a pressure tank, it also works as an expansion tank, so you don't need another tank. I would not put the pressure relief valve at the well head or on top or air side of the tank. It needs to go on the water line at or after the pressure tank.

 

[Sponsor]

 

[LLigetfa]

does it matter if I put it at well head or on top of bladerless pressure tank?

A small air leak would be hard to detect and could bleed off all the air and short-cycle the pump to death.

Not sure why Cary is averse to putting it at the wellhead. If a PRV were to pop off, I'd rather it do it outside where it can be seen and the water not cause damage. You could of course plumb a discharge pipe out the side of the house where it can be seen.

If you have anything inline that could fail or clog such as a topside check valve or filter, it would be best to have the PRV before those.

 

[ugabulldog]

the expansion tank is code that is why I have both, and there is no relief valve on tank. I have a check valve before pressure tank but also one down well pipe so no way to put prv before that one.

 

[Valveman]

The PRV needs to at least be after the last check valve, or it cannot do anything for thermal expansion.

 

[Reach4]

The PRV needs to at least be after the last check valve, or it cannot do anything for thermal expansion.

ugabulldog has a thermal expansion tank.

 

[LLigetfa]

The PRV needs to at least be after the last check valve, or it cannot do anything for thermal expansion.

The water heater would have a T&P valve to satisfy that need. I suggest the OP use a PRV to prevent a blockage from deadheading the pump.

 

[ugabulldog]

So I should put a PRV at well head and would be ok without one at water tank since I have one on water heater?

 

[Valveman]

The T&P valve on the water heater won't pop off until 150 PSI. I would still want a 75 PSI relief valve at the pressure tank after the last check valve.

 

[ugabulldog]

If I have a pressure relief valve at well head, why wouldn't this protect everything downstream as well?

 

[Valveman]

Because the check valve at the tank will keep that PRV from seeing anything that happens due to thermal expansion. Also because after you get this figured out you are going to realize you have a cycling problem, then there can be no pressure relief valve prior to a Cycle Stop Valve. Trying to keep you from having to move the pressure relief valve after adding a CSV, like I have to tell people everyday.