PRV Leaking on/off

Neil_5

I had a new AO Smith 50 gal DHW tank installed, after 2 weeks I had a small amount of water comming out of the PT valve when the unit is cooking. Had the installer return and install an expansion tank. Now 4 weeks later the same thing again. I will call the installer, just want to know what can be the cause of this?

Neil

Robert O'Connor_7

Leak..

Sounds like the pressure to me. Check the incomming water pressure, If it exceeds 80psi you should install a pressure reducing valve on the main. The expansion tank will only help if pressures are within the valves spring range..Robert O'Connor/NJ

Neil_5

Expansion Tank Check

Robert:

Thanks for your reply, thats next on my check list, will see what the incomming pressure is.

Regarding the expansion tank that was installed on my cold inlet line, I did not see the installer prep the tank, is there anything I can check. Can I do the following?

Turn off main and drain out tank.
Unscrew tank and empty out all water and check for pressure?
The pressure of the tank will be listed on the tank? if low, pump up the pressure?

Just want to make sure that the expansion tank was prep properly.

Thanks,
Neil

Canuck

Well or Municipal Water

Along with ensuring that the precharge on the expansion tank is in-line with the system water pressure, I find that you need to oversize the expansion tank if you're on a well. This is due to the fact that there is a check valve in the discharge line of the well pump, which locks the water in the system and can create a situation, whereby the system is overpressurized to a point that it is beyond even what the expansion tank can absorb. The scenario is usually like this:

1)Day's end, someone has a shower, last load of laundry or dishes in dishwasher - then everyone is in bed. No more water consumption.

2)Pump has refilled system and cushion tank to setpoint pressure (40-60 psi).

3)Water heater has responded to aquastats 'call-for-heat'.

4)Depending on the duration of fire, setpoint pressure and storage temperature, I've seen this scenario push the system pressure well over 125 psi.

If you're not on a well but have a backflow prevention device (BFP) on your municipal line, (certain municipalities here in Canada are mandating installation in all buildings - even residential - to protect the central water supply), then the same situation may occur.

jim lockard

40 Psi

most tanks are shipped @ 40 psi you will need to check your incoming water pressure and match the tank pressure to that. Best wishes J.Lockard

Neil_5

Update

I had the expansion tank cushion busted. Bought a pressure guage from HD and house pressure was 70 and would spike to 140 max over a 48 hr period. Called in plumber and had a pressure reducer installed to 50 psi and a new tank installed. Hooked up gauge and am reading 50 psi so far, will see how far it spike overnight.

Neil