shallow well & cistern help needed!

[twodogs]

I have a shallow well pump hooked up to my 1000 gallon cistern. I have a simer 1/2 hp convertible shallow well jet pump. I can't get it to run at the proper pressure. I have a 30/50 switch, but I can't seem to get the pump to run until it hits 50 lbs. The pump labors forever, so I end up shutting it down. I have set the pressure tank to a 18 lbs & adjusted the switch to be a 20/40 switch, but the tank ends up emptying out, the pump looses its prime. Should I start over with an empty tank? The water isn't been carried that far to the pump - less than 25'. I am at a loss. I have read several threads, & I do not have a check valve on the line - didn't know if that was necessary. The drawings that I had for install didn't show it.

Any help will be greatly appreciated!

 

[Bob NH]

You need a check valve somewhere between the source (the cistern) and the pressure tank. Otherwise, the water will flow from the pressure tank back to the cistern as soon as the pump turns off.

The usual place is in the cistern or at the outlet of the cistern. You can probably install it "wet" (without emptying the cistern) if you get everything ready. You will get a little wet.

If the pressure switch is on the pump (often the case) then you can't put the check valve between the pump and the pressure tank; else the switch will not measure pressure when the pump turns off.

The manual that I found http://www.simerpumps.com/pdf/SIM569.pdf shows the check valve at the inlet of the pump.

The pump is supposed to be able to pump to 50 psi with 25 ft of lift so it should do well with a cistern.

The best way to install the pump is near the cistern elevation with the inlet pipe rising slightly from the cistern to the pump, and absolutely no high spots between the cistern and the pump. That allows any air to travel to and out of the pump. If there is a high spot in the pipe it can collect a bubble of air that prevents flow.

It will also work if it runs down from cistern to pump as long as there is no high spot in the line or any down-pointing inlet in the tank. I have seen those inlets collect a bubble and prevent flow out of the tank. If there is one of those things in your tank, then take a stick and tilt it until it points sideways.