Water Wizard Problem


My Jim Coleman Water Wizard stopped delivering presoak!  (I only run one presoak and the system is closed to high pressure but does use air.)  The problem I am having is I am getting pressure buildup on the outward side of the check valve which does not allow the valve to open.  What does not make any sense is how the pressure builds up.  I ran the presoak function for about 10 minutes and it worked fine.  Ran a couple cars through still no problem.  It just quits working whenever it feels like it!