Pressure System Diagnosis

[260 Rem]

System consists of a deep well pump feeding a pressure tank with a standard switch and gauge. Lately, a noticeable pressure drop occurs when the cut-in engages. Very short, more like a pulse. Watched the pressure drawdown on the gauge, and when the cut-in engages, the dial “flickers” downward about 10 lbs (only about 1 second), then jumps back to the cut-in pressure as the pump starts. Have never noticed this “pulse” previously...what’s up?

[CaberTosser]

The pulse you're likely seeing is from when the check valve is opening. Have you checked the pre-charge pressure on your expansion tank (to get a true reading this is the pressure when the water pump is turned off and the water has been drained, so that you're just getting the air pressure reading of the expansion tank)

[roger]

is this pressure tank a captive air style often blue or red with air valve on it or is it a galvanized tank.
is this water pump short cycling? or does pump comes on when you turn on the tap?

[260 Rem]

Tank is a pre-charged unit with a bladder and does not cycle when water runs so probably not water logged.
I was unaware there is a check valve but that makes some sense. Where is it? I presume if the check valve is buggered, the pressure tank will need to be replaced? I will empty the tank to confirm precharge pressure is a bit under the cut-in.
Thanks

[Sashi]

If it drops 10 lbs in 1 second, chances are your bladder is no longer charged.

[260 Rem]

It drops from 30 to 20 the instant the cut-in activates ....and then back up to 30 in less than a second. Kind of looks like a new tank, switch, gauge ... get changed out. Just part of the joy of rural living.

[gmcmax05]

Is it causing problems? Or you just don't like that the gauge drops for a fraction of a second.

[260 Rem]

It is not causing problems ... started noticing it in the shower... just a “blip”, but definite drop in pressure, then return to what it was a few seconds previous. It was that symptom that had me watch the pressure gauge to see what was happening. Has not ever done this before, so is a symptom of something going wrong. Best to get on it before it fails. Found the receipt for the last time I changed the pressure tank out...in 2000.

[ChrisGrohms]

At what pressure does the gauge fluctuate? What pressure switch do you have ? 30/50 or 40/60? If the bladder pressure is not 2 psi lower than cut in pressure then this is usually a symptom. If cutin pressure and bladder pressure are close to each other let a few psi out of the bladder.

[260 Rem]

It’s a 30-50 switch...I have bled a bit of air but really need to empty the tank to get an accurate assessment of the bladder pressure.

[260 Rem]

I think I got it thanks to the good advice ... and a bit embarrased to say my “tinkering” without really understanding what I was doing ... was the likely problem. At some point I had “adjusted” the pressure range ... When I drained the tank, found the cut-in was lower than the bladder pressure. All reset now with bladder pressure at 28 and I set the cut-in to 32. Did I get it right?

[ChrisGrohms]

2 psi below cut in is recommended but 4 psi won't hurt.