Low pressure problems

My low pressure functions were not working in any bay.  The equipment room floor was wet and one wall in the bays was wet.  The presoak and tire cleaner was not working and when you disconnected the hose from the pump to the solenoid block the pump worked fine.

I really had no clue so I called Greg and he enlightened me on what the problem was.  I removed the check valves between the solenoid bank and the pump.  Then pressed on them with a screwdriver then reattached.  Both functions worked fine so I turned on the high pressure one bay at a time to try and find the broken low pressure check valve.  I had no luck.  The problem was the presoak and tire cleaner use the same check valve in the bay.  Which confused me with trouble shooting but not Greg.