I'm on a water well system & a check value is installed between the well pressure tank and the Hot water heater.

I think the check value is limiting the expansion of hot water & causing the T&P value on the hot water heater to open periododicly.

Will installing a small hot water expansion tank most likely fix the T& P value from releasing water?

What should I set the precharge pressure on the small expansion tank ? My well pump is set cycle on at 30psi and shut off at 50psi.

Hello DD:

Yes... installing an expansion tank should help to eliminate the issue. Install the expansion tank in the cold water supply to the water heater (after shutoff, but before vacuum breaker if present) on the horizontal if possible (less stress on nipple of expansion tank), and a hanger is always a good idea.. ;) . You will need to know the SIZE of your water heater to purchase properly sized expansion tank.

So need:

1 - 1/2" copper x 1/2" female threaded tee (if 1/2" pipe)
1 - roll teflon tape
solder, flux, sandcloth, and torch
1 - expansion tank.
1 or 2 hangers (could be strap hangers or 3/8" threaded rod, 3/8" plate and split hanger)

Most tanks come precharged, but read the instructions that come with the tank and set the pressure as suggested.

Let us know if need more... and result. Good luck!. Mark


If this helped, please RATE THIS ANSWER. Thank you.

I got a small 35 gallon water heater so I got a small 2 gallon hot water expansion tank(Watts DET-5)..

The directions say to open faucet to allow the system pressure to equalize. Then set the pre-charge on the hot water expansion tank to that pressure.

But I'm on a well and system pressure keeps dropping until it reaches around 30 psi , and then the well pump comes on and recharges the well expansion tank/system back up to around 50 psi.

So what do I set the Pre-charge too?

I read somewhere that >>>>
Expansion tanks are pre-charged with a 40 PSI air charge. If the inlet
Water pressure is higher than 40 PSI, the expansion tank's air pressure
Must be adjusted to match that pressure but must not be higher than
80 PSI.<<<<<<<

So do I set the Pre-charge on the hot water expansion tank too 50 psi then?
... or should I just leave it at the 40 psi it comes from the factory with?

Hey DD... According to Emerson Swan (manufacturer of these tanks)... 49 PSI is correct setting... try it out. Let us know how it goes... Mark