Undercharged Pressure Tanks

[rural_engineer]

My well pump operates on a 50/70 pressure switch and I have a 60PSI CSV in my well, which seems to give just over 50 PSI at the house when the water runs continuously. (It's about 16-18' vertically from the well to the house.) My plumbers aren't very knowledgeable, and I believe installed the pressure tank and the hot water expansion tank without setting the pre-charge.

I believe the factory pre-charge is 50psi for the thermal expansion tank, and 40psi for the well tank. Have I damaged or am I going to damage the tanks by operating as-is for a while?

 

[Reach4]

I believe the factory pre-charge is 50psi for the thermal expansion tank

I would set the thermal expansion tank to 70 psi with a 70 psi cutoff. Usually with a pressure tank, there is no thermal expansion tank needed.

https://cyclestopvalves.com/pages/csv1a-installation-instructions says

Note: Do not install pressure switch directly on main line away from pressure tank. Pre-charge pressure in the tank should be 2-5 psi lower than pressure switch start point.​

So maybe set the pressure tank air precharge to 47 if your pressure switch cuts on at 50.

 

[Sponsor]

 

[Valveman]

With a 50/70 switch I would set the pre-charge in both tanks at 45 PSI. Like Reach says you don't usually need an expansion tank when you have a well pressure tank, as it also doubles as an expansion tank. With 45 PSI in both they will both act as pressure tanks and will still function fine for expansion as well.

 

[rural_engineer]

I originally wasn't planning on having an expansion tank since I had a pressure tank. However, there are a couple valves between the pressure tank and the water heater which could be closed that would put the water heater on a sealed system. I figured it was safer to make it idiot proof.

Is there any harm with having the tanks sit at the manufacturer's precharge until I have a chance to get down in the crawlspace with a pump and pressure gauge?

 

[Reach4]

Is there any harm with having the tanks sit at the manufacturer's precharge until I have a chance to get down in the crawlspace with a pump and pressure gauge?

No, since you have the pressure tank also.

 

[Jadnashua]

If the pressure tank(s) is(are) set higher than the turn-on trip point...there will be NO water stored in the tank (at least that could be pushed out) before the pump has a chance to turn on, so there will be a slight hiccup. IOW, the tanks will empty before the pressure plunges, and the pump turns on. Now, whether that would damage anything, don't know.