SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Last year I installed a new system. I have a 4" line coming from the irrigation canal 1/4 mile away with a elevation drop of about 25' feet to feed my 2 hp pump. This drop gives me about 4-6 PSI on the inlet. I have 4 stations of rain birds with maxi paws with 10- 12 heads each. The heads are feed by a 1 1/4" line to 1 " laterals then to the heads. After about 25- 30 minutes of pumping without any problems, I can hear the pump making noises ( not smooth as when water present ) the pressure drops until no water is pumped to the sprinkler heads. I will then open a valve about 100' back on the 4" line, the flow is slow a first but then it gradually increases the flow to where I then can resume operation of the pump. Its like the water stops flowing to the inlet.


I've added an air vent back along the 4" line, this hasn't solved the problem.

Do I need more air vents or a check valve.