Irrigation pump won't stay primed

[Irrigation123]

I have multiple ongoing issues with a friend on mine's irrigation pump and I am trying to find some help. He has a Red Lion 1HP jet pump. Installed it over a year ago and works great at first. Irrigation runs great for a few days. After a couple of days the pump will not reach shut off pressure and will continuously run causing the schedule 40 PVC pipes. to basically melt. I have lowered the shut off pressure multiple times. Same thing happens. So I decided to put it on a Monroe Smartbox. Worked great for like a year. Now it won't stay primed and the Monroe box shuts it off after a minute because of low pressure. If you restart it after the Monroe box shuts it off, it almost always reprimes immediately.
I have changed the check valve several times. Never seems to be the issue. Valves are not wheeping
I tried installing a brand new irrigation pump to replace the Jet Pump and it will not prime to save my life. Reinstalled the Jet pump and took the Monroe box away. It primed immediately but again having the same issue where after a few days it will not reach cutoff pressure and heats the pipes up and melts them.
Well is a shallow well. Water is about 10' down. Draw pipe is about about 16' down. Pressure switch is set as low as 50lbs of pressure. Jet nozzle does not seem clogged or obstructed.

 

[Valveman]

Sounds like you have a suction leak. Probably right where plastic pipe screws into the pump. Use foamy shaving cream on the connections and you can see a hole suck in the foam where the leak is.

Also, should use a metal nipple on the suction side for a foot or so. This gets the first plastic connection far enough away from the pump that the heat won't cause the threads to leak air in.

 

[havasu]

I've never considered using shaving cream. A great idea!

 

[RS]

You say the water level is at 10 feet down, but does it stay there with the pump running? It could be pumping the well down below the suction pipe and loosing it's prime that way. Putting the suction pipe down 30 feet will prevent that from happening, if the well is that deep. It will draw the water level down to about 25 feet and then only pump as much as the well recovers.