Momentary Pressure Drop Just as Well Pump Starts

[MarkerB]

Y'all!

I've got a 250' foot well. The 240V submersible pump, check valve, drop pipe, wiring, tank, and gauge were all replaced 4 years ago. Recently the 30/50 pressure switch wasn't cutting off, even at 70psi, so I replaced it.

Now the new pressure switch works fine most of the time, but every few days its low pressure safety protection trips, and I have to reset it. This is going to be really bad in the winter, as it's all in a pump house outside.

I took a video of several pump cycles, so it's easy to see what's happening. Just when the pressure switch calls for the pump to start at the low point of 30psi, there's a big extra drop in pressure to 20psi or lower, before the pump actually can get the pressure up again. This happens for each cycle, and it looks like sometimes the pressure momentarily drops enough that the low pressure safety engages.

Why would the pressure drop a whole lot, but just for a moment, when the pump starts? When I reset the switch, the pressure immediately comes up to 35PSI.

I also hear two clicks from the pressure switch, in rapid succession, each time the pump starts... or each time it stops. The double click sounds coincide with the pressure drop. A clue?

I checked the voltage, and it's solid even when the pump starts.

I raised the cut in/cut out pressure about 5PSI, and now it happens less... but still happens. It will happen more often when I'm consuming a lot of water, which kind of makes sense.

Here's a video of both a successful cycle, and one where the safety mode is tripped. Please ignore the very active spider, and the temporarily shoddy electrical cabling!

Thanks,
Mark

 

[Valveman]

A short delay on water delivery while the pump is starting is caused by having too much air pressure in the tank.

 

[Sponsor]

 

[Reach4]

I was not expecting to see a tank tee, but there it is. Tank tee is good for making sure that the tank and pressure switch see the same pressure.

1. With the water pressure in the upper 80% of its normal range, what does the water pressure gauge say? What does the air pressure measure at that time?
2. With the water pressure at zero, what does the air pressure measure?

Not related to this, but usually it would be best to not have the check valve at the tank. You could remove the innards.

 

[Valveman]

After watching the video that is a pretty long delay in water delivery. Remove that check valve prior to the pressure tank. Your lower check maybe leaking back.

 

[MarkerB]

Thanks for the quick responses! What a great community.

I didn't even notice the upper check valve before. I wonder why the guy who replaced everything left it there. Why would anyone install one at the top? It's not a very deep well.

I'll have to get the stuff together to check the air pressure, which I've never done before. Wait a sec... I wonder if my previous switch was actually 40/60, which would result in the tank pressure being too high for the new switch. Could that be the primary problem here?

 

[Valveman]

Ding, ding, ding, we may have a winner! Turn the large screw in the 30/50 pressure switch about 3 turns to the right and make it a 40/60.

 

[MarkerB]

Yes! That was the fix. I turned the main adjustment up to 41/62 (if I trust the gauge), and there is now no pressure drop when the pumps starts. I'm confident that will fix the safety trip problem.

Square D is supposed to list the factory-set pressure range directly on the switch cover, but I couldn't find it anywhere on the old one. So I bought the very common 30/50 as a replacement, and didn't even think about the storage tank needing to be synced to the switch pressure setting.

Thank you all so much!