isit hooked to the pump start relay on the controller?

skytrain, I seem to be missing something. When the pump shuts down, the whole system on the delivery side of the pump should 'bleed off' through the sprinkler heads. No water under pressure ought to be present anywhere. The piping between the non-return valve and the pump on the supply side would contain water for 'priming' the pump for the next use. This can leak away but you will find that the pump will take longer to 'prime' the next time. Does the system have an air tank? And might this be part of the problem? Two questions for which I have no answers.