Author Topic: Shallow well losing prime  (Read 984 times)

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Shallow well losing prime
« on: May 23, 2023, 04:59:36 PM »
I'm restoring an old well here. Everything outside is brand new. Water is consistently at the pump (no leaks on the inlet) and I run the sprinklers at 45/62 with the CSV set at 58.

Sporadically (now quite often) the gauges at the pump/tank/CSV all show about 30 PSI, and it's acting as if it's trying to prime.

The pump is a heavy old cast iron F&W 1hp and there's an old galvanized tank with Merrill Float installed (not a bladder and no Schrader valve) and a threaded plug on top.  I have the switch on the CSV. The CSV outlet goes down to a tee which goes to the sprinklers and the other side of the tee down to the tank. (I only get rapid cycling for a few seconds when the ball valve between the CSV and the tee is closed during initial priming.)

I can easily reprime by closing the ball valve, turning on the pump, and slowly opening the ball valve to fill the tank. Other times, assuming it's waterlogged, I have to drain the tank, unscrew the top plug to let air in, replug, and refill.

Now, before I lift that heavy pump up off the check valve (again) to tighten the spring on the check valve, I figured I'd ask the following question just in case...

Could having the sprinkler outlet between the CSV and the tank be causing this issue?

I figure eventually I will just replace the large galvanized tank with a smaller tank since I have the CSV now, but I'd like to solve this first. I notice the pump initially pulls around 60 PSI when I go to reprime with the ball valve closed. I wonder if running at 60/80 would give it more suction at cut-in vs 45 and therefore prevent it from losing prime. Of course, I'd like to figure out why this is happening, though.

Cary Austin

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Re: Shallow well losing prime
« Reply #1 on: May 25, 2023, 06:55:20 AM »
I would not turn up the pressure. That pump will probably not be able to build that much pressure.  Pumps do not normally loose prime when running unless there is a leak in the suction pipe.  But 30 PSI is usually the number when there is something obstructing the jet nozzle in the pump. 

If the pump is cycling while running the irrigation because the sprinklers are attached before the CSV, then it could be losing prime when it is shut down.