Is my well pressure tank permanently waterlogged, do you think?
I have a private well that's about 100 ft deep. I have an old WellMate WM-25WB pressure tank. It's fed by an old Myers ¾ HP submersible pump. The property is new-to-me. I noticed what I think is the pump short cycling. In between a start and stop of the pump I get about 4 gal. I think this is considerably less than the drawdown capability of this 86 gal tank and the pressure switch settings.
I listened for the pressure switch clicks and then read the gage – 39.5 psi start, 57.5 psi stop.
Here's what I did:
-No water came out of the schrader valve.
-Emptied tank to 0 psi through the iSpring filter (sits about 2.5 ft above bottom of tank). Still has water in the tank as felt by gently rocking the tank.
-Added more air to the tank, to get 38 psi.
-Continued to pump out water via iSpring.
-Got down to about 10-15 psi in the tank and the water turned very dark rusty. (This area is known for high Fe and Mn in the groundwater at 100 ft.) And then the water stopped flowing.
-Tank rocked easily.
-Added air to get 37.5 psi at the tank.
-Flushed and flushed to get rid of the rusty water. I assume just the dregs of the tank.
-After all diagnostics and flushing, a pump cycle yielded about 16 gal (a big increase).
What do you think? Any additional diagnostics I can do? Thanks.
John
Best Answer
Start shopping for a new tank - your diagnostics indicate that you almost certainly have a failed bladder on a 20+ year old tank.
You can continue to add air as needed until you get the new tank, but it's tedious to do so. There's not much need to do the full drain and pre-charge when the tank won't hold the pre-charge pressure.
You may eventually have a more drastic failure if the tank corrodes enough, so it's good to take the time to shop carefully when the failure mode is non-critical, rather than having to pay "Whatever it costs to fix it NOW" when a more drastic failure is spewing water.