Piston pump early cut off with chatter

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Dougw

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Joined
Sep 22, 2020
Messages
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Location
St. Catharines Ontario
Hello.
I'm currently using a pompco s-275 piston pump on my well. It is working fine but sometimes cannot keep up with the water demand in the house barely increasing the pressure in the system/expansion tank while a shower is running. I decided to rebuild an s-450 ( higher volume unit) and have a problem. The rebuilt pump runs great when pumping directly from the well without pressurizing the system. The pump will kick on at the cut in pressure of 40psi but the switch chatters and stops at 45psi not the 60 cut off pressure.

Brand new pressure switch. Tried A known good switch with same results.

Air bladder is at 38 psi, not waterlogged. System works normally with slower pump in place.

Any advice is appreciated.
 
Thanks for the response. The pressure switch is mounted on the pump by manufacturer with a pressure line for the switch from the pump housing. The pressure tank is about 20" away.

Received a call from the pump manufacturer's rep. After discussing it he believes that the higher capacity pump isn't getting enough supply through the old, probably restricted feed line when building the pressure in the system.
 
I don't think so! The larger pump is sending more water to the pressure tank and the tank being 20' away form the pressure switch is not good. The pressure will reach 60 at the switch long before the tank accepts the water. Move the pressure switch to the base of the tank and the chatter will go away.
 
Valveman said:
I don't think so! The larger pump is sending more water to the pressure tank and the tank being 20' away form the pressure switch is not good. The pressure will reach 60 at the switch long before the tank accepts the water. Move the pressure switch to the base of the tank and the chatter will go away.
Click to expand...
The pump is 20 inches away. ;)
 
That is the s-275 pump in place working as expected. The s-450 hooked in the same position is the one shutting off early.
The setup hasn't changed since I've owned the house (except a new pump 3 years ago) and I'm sure it was like that for a long time as the previous owner had 2 old pumps off to the side.
 
Yeah that sensing tube for the pressure switch should be plumbed on the line going into the pressure tank. The pressure switch is too far from the tank to get any cushion.
 
Thanks. air charge is 2.5 psi below cut in.
How far from pump would you suggest? Is it okay for it to be on the line after the pressure tank?
 
After the tank should be ok, but I prefer on the line going into the tank as there are no elbows or bends between the tank inlet and pressure switch that way.
 
That will probably work because the galvanized is most likely rusted up on the inside (smaller ID) and is restricting the flow, which is why the switch is bouncing.
 
Should I be replacing the lines between the tank and the pump? What material do you suggest ?(galvanized, PEX)
Replacing the pump to well side is a non starter and cannot be done in my circumstance.
 
Apparently galvanized has worked fine for many years. But I prefer copper or PVC. While you are at it put that pressure switch connection at the base of the tank.
 
Thanks for the help. I did the job today, with the help of my father-in-law, and everything is working well now. I had to move the pressure switch further away from the pump as you suggested. It took a couple of tries to get it far enough that the bounce didn't cause an issue. My local hardware store suggested PEX with plastic fittings for wells in our area.
All in all went pretty smooth.

Thanks again
Doug
 
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