My property has a lawn irrigation system that is supplied by a shallow well. It has worked satisfactorily for the last 4 years that I've owned the property. Recently the pump lost prime and I had no spray from any zone. I replaced the check valve in the supply line - it was allowing water to drain back and the pump was losing prime.
After replacement of the check valve the pump primed and all 5 zones worked well upon testing until the next scheduled cycle. When the system starts the sprinkles will pop up and spray then sink back down and it will take between 2 to 5 minutes for the first zone to start spraying fully and then the system runs correctly through the cycle. I can turn the system off for several hours or longer and repeat this scenario starting on any of the 5 zones.
I've hooked up a line from city water to the pump priming hole and everything works properly, water flows from the sprinklers quickly.
I did repair a leak at the gasket at the end case of the pump. I can find no leaks on the supply side for the area I can see. I have started to dig up the supply side line with the intent of checking for leaks and replacing the foot valve but I've found the line splits at a tee and it appears there are at least 4 pipes that are teed into the ground to supply water to the one pump that is in the system. The vertically teed pipes are around 6' to 8' apart for the ones I can see. I haven't dug up the whole supply side lines at this time. I can only assume that all vertical drops have a foot valve on them but that is just an assumption at this point.
With all this said my thought to solving the problem was water was draining back at a point before the check valve. Does this seem like a reasonable conclusion?
What else should I be looking for that may cause this problem?
What is the best way to find a leak, if there is one, on the supply line. I dread having to dig up all the lines.
Any input will be appreciated. Thank you.