New Sprinkler Pump losing Prime after 12 hours with new Check Valve, Zone Valve and plumbing

[MisterNick]

We just had our existing well sprinkler pump replaced with a Red Lion 97101501 RL-SPRK150 44 PSI Cast Iron Self-Priming Lawn Sprinkler Pump. The vendor also replaced the check valve (not sure the brand but it is metal verses plastic), the zone valve with a K-RAIN 4404 4000 Series Indexing Valve with 4 Outlets and 4 Zones, and all the PVC from the check valve to below the ground under the zone valve. The issue is that sometime between 12 and 24 hours of the pump being off, the pump loses prime. The check valve was tested before installation. I believe the issue is related to how the plumbing between the pump and zone valve was done. It appears an alignment mistake was made and instead of the PVC coming straight out the pump and across to the zone valve as was previously done and is the way every other sprinkler system I have every seen is plumbed, the vendor plumbed the pipe up out of the pump to down under the ground, across about 12” then back up about 3’ and turned left going into the zone valve, essentially creating a big “U trap” between the pump and the zone valve. I believe this is creating an air lock and the reason the pump loses prime after 12 hours. Also the height of the pipe above the pump where it bends to head underground is higher than the zone valve. I attached a pic for reference. Assuming the check valve, or debris in the well or the pump or zone valve, and plumbing connections are not leaking or defective, can anyone please explain why the pump loses prime and if this weird “U trap” plumbing is the issue?

 

[Valveman]

Nothing on the discharge side should have anything to do with losing prime. Either you have a leak in the suction line or the foot valve is leaking back. There is not much pressure to hold a foot valve closed without a pressure tank system, so the type of foot valve is important. A spring loaded type check valve should be better than a flapper type. There are only two kinds of valves made in this world which is those that leak, and those that will leak. Just because the foot valve is new doesn't mean it is holding.

 

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[WorthFlorida]

When the pump shuts off and after a few minutes to allow water in the irrigation zone to drain out some, place your ear near the check valve or intake pipe. If you heard water running or gurgling, the water is draining back down the pipe. In Florida. irrigation wells will rarely have a foot valve. Depending where you are in Florida, hydrostatic pressure will bring the water up to about five feet below grade, at least in Palm Beach County. If you're drawing from a lake a check valve will be usually under water near the screened intake.

I had a $180 2" brass check valve spring loaded never held prime. I tried everything. Finally I had an irrigation company check it out, they replaced the check valve with a spring loaded PVC one and never had a problem after that.