Diagnosing drop in pressure after pump shuts off

[audiolab1]

Hello,

We have lived in our lake front home for 7 years and never had any issues with our water system. We draw water from the lake with a Jacuzzi 1/2HP pump. Before going into my system symptoms I should also state that we have never had a no-water situation in the house and that I am confident working with most of the systems inside our utility room including the pressure switch. Pumps I have little to no experience with. The pressure tank pressure is checked twice a year and never requires topping up.

We’ve noticed lately that when taking a shower the pump is cycling on for about 10 seconds and is only off for about 20 seconds before cycling on again. There is also a much larger drop in water pressure when the pump cycles off than I remember having in the past. Thinking that maybe our carbon filter is due for replacement (the 5 micron sediment filter was only replaced a couple of weeks ago), I removed the carbon filter and noticed that the cycle times improved only slightly. I had checked the pressure tank pre-charge pressure a few months ago, but I drained the tank and checked it again and it is still reading exactly 28 psi. I noticed that the pump turn on and cut off pressures were slightly low (maybe 28/48 PSI) so I adjusted the pressure switch to bring them up to 30/50 psi. Now the pump is running for about 20 seconds with just the shower running on full and the cycle time is about 30 seconds. If I open the kitchen faucet and leave the shower running, the pump runs for about 45 seconds before shutting off and does not cycle on again for about 90 seconds. This seems to be short cycling to me and I’m suspecting the pressure tank, even though the pre-charge pressure is holding. Other than the short cycle time and the drop in water pressure when the pump shuts off (confirmed by observing the pressure gauge at the inlet side of the tank), I am also noticing that the pump tends to kick on as soon as we use water, assuming that no water has been used for a little while. I have not noticed the pump cycling on it's own when no water is being used, but I will look into checking that. I'm doubting any problems with the pump as it has no problem getting the system to the cut-off pressure, even if I run multiple faucets in the house.

Many thanks for any insight you might be able to share. I desperately want to have this issue diagnosed and repaired before winter!

AW

 

[Valveman]

You didn't say how big the tank is? But you can have 28 PSI in the tank even when water has gotten on top of the diaphragm. Many times the pressure will even increase without having added anymore air. Either way if the pump comes on the instant you open a faucet, the tank is most likely bad.

 

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[LLigetfa]

Now the pump is running for about 20 seconds with just the shower running on full and the cycle time is about 30 seconds. If I open the kitchen faucet and leave the shower running, the pump runs for about 45 seconds before shutting off and does not cycle on again for about 90 seconds.

That does not make sense. Why would the pump only stay off for 30 seconds with just the shower but stay off for 90 seconds with both the shower and kitchen faucet?

 

[audiolab1]

You didn't say how big the tank is? But you can have 28 PSI in the tank even when water has gotten on top of the diaphragm. Many times the pressure will even increase without having added anymore air. Either way if the pump comes on the instant you open a faucet, the tank is most likely bad.

Our pressure tank is a Well-X-Trol WX-202, so 20 gallons.

Do you think that the pressure drop after pump turn off could be a bad tank?

In speaking to a local water system tech, he asked if I tried lifting the tank when it was drained to see if was still heavy. I have not yet tried this. He suggested that if the tank is not full of water it would be a bad pressure switch, i.e. some small clog or blockage. I don't understand how this could be? Does the the pressure switch contain some sort of valve?

Thank you for your response!

 

[audiolab1]

That does not make sense. Why would the pump only stay off for 30 seconds with just the shower but stay off for 90 seconds with both the shower and kitchen faucet?

I might have the off time incorrect...sorry about that. Of course it makes sense that the time between an off and then on pump cycle should be shorter for higher water draw. Could a check valve somewhere in the system be the problem? My understanding is that a bad check valve at the pump would cause loss of water after the system sits for some time. Maybe there is a check valve somewhere inside the house?

 

[Valveman]

A 20 gallon tank only holds 5 gallons of water. A 1/2HP pump should not be able to fill that tank in 10 seconds. That means either you have a 30 GPM pump, which isn't possible, or the tank is not holding 5 gallons as it should.

Pressure dropping after the pump shuts off means water is going somewhere. If you are sure there is no water leaking towards the house, the check valve must be leaking back to the well. All of these problems are caused by the pump cycling on and off too much. The bladder in the tank and check valves cannot take cycling without wearing out and causing problems.