Pressure rises after pump shuts off

[JohnBoyJimBob]

I was servicing an older residential system which has an ordinary new fibreglass pressure tank and new pressure switch, pumping from a submersible pump inside a drilled well. Switch turns pump on at 30 PSI, off at 50 PSI, as expected. Tank is normally pressurized to 28 PSI.

What I can't explain: after the pressure switch shuts off the pump, the system pressure continues to rise another 15 PSI.

Any explanations for this behavior?

 

[Reach4]

Unusual. One explanation could be that the nipple or inlet to the pressure gauge is mostly clogged. You could put a garden hose thread pressure gauge on the tank drain spigot, and see if that pressure rises faster than the regular pressure gauge.

 

[Sponsor]

 

[LLigetfa]

new fibreglass pressure tank and new pressure switch

Where is the switch in relation to the tank? Where is the gauge in relation to the tank? Is there only that one tank?

 

[Valveman]

Had one like that driving me crazy. Found out there was an old tank buried in the yard. The old tank would pressure up to 100 PSI before the new tank hit 60 and shut off the pump. Then the pressure from the old tank would bleed over to the new tank and pressure would increase.