Plumbing – Replacing a well pressure tank

Allowing for the possibility that it could be otherwise as diagnosis via internet is imperfect....

I see both a pump problem and a check valve problem here. While they may be located in the same place (if your only check valve is on the pump - which is the way mine is set up) they are not the same thing...though I also see another possibility that would do both.

• Pump problem - pressure not getting above 27 PSI, or 15 with a faucet open.
• Check valve problem - when you shut off the pump the pressure drops to zero - unless you are using water, the pressure should stay at 27 if it was pumped up to 27. When you only had 10 PSI in the tank, there should have been some water storage - when raised to 38, no water could possibly make it into the tank, since that's designed for 40/60 PSI operation and won't take any water until the the water is over 38 PSI.

The third possibility - you have a leak in the pipe above the pump and check valve - so the pressure is limited, and the water drains away from the leak without the check valve being to blame. If you can go and listen at the top of the well while someone else turns the pump on, you might actually hear this leak, if its in the well above waterline. Or you might have a recently soggy spot in the yard if it's after the pipe leaves the well.

While I don't think it's to blame in this problem, I'd also suggest rechecking your tank pre-charge to see if it has stayed at 38 PSI or started to fall again. Often when the precharge becomes low it's not simply a matter of needing to add air - it's a failure in the bladder or diaphragm.

The Pressure gauge reading cycles between the pump cut-in and cut-out pressures. Sounds like the gauge is dead and permanently stuck at 24psi.

Often, the cut-in and cut-out pressures will be listed on the pressure switch and commonly are 20psi cut-in and 40psi cut-out. So your water pressure on the gauge will cycle between 20 and 40psi during water usage.

The tank has a built-in bladder that is pre-charged to 30psi when your gauge reading is 0psi (pump breaker turned off, water tank drained). There should be a faucet somewhere on the pump manifold system that allows you to drain the pressure tank of water so you can check the bladder air pressure.

To repair the gauge, I would switch the power to the pump off, drain the tank and simultaneously, replace the gauge and check the bladder pressure and top it off if needed. Then power the pump back up.

If there is a lever on the side of the pressure switch (image below), it is a low pressure cutout to prevent the pump from operating if the well runs dry. Pull it up till the pump turns on and hold till the pump stays on (about 10-15psi). With no low pressure cutout, just power the pump on and it will automatically do the rest.

Once you have a working gauge, you can start to determine whether it is a pump pressure supply issue, or if you have something more serious like a restriction in the house supply line or a leak.

Do you have any sort of sedimentation filter in your water system? Sounds like it may have clogged and if a screen, needs flushed or replaced if it's one of those string filters.