Question
Hi - I don't know much about well pumps, but my boyfriend does.  He just installed a Gould's 1 hp shallow well pump in his yard and hooked it up to an irrigation system.  It has a pressure tank, 1 way check valve (this I know)....so we ran the sprinklers through twice and both times the pressure is dropping (very slowly) from 60 psi to 51 psi.  We haven't been home during the day to see if it drops to 40 at which time it turns itself on to prime.  We have checked the selenoids and all pipes are clean (no kinks).  Do you have any suggestions of why pressure may be dropping?  Thanks!!

Answer
Sandra,
You probably have a leak in the sprinkler system main line piping . That is what it sounds like to me. The gauge is dropping because you are losing water through the leak.

The problem is that it may not be easy to find. The other thing is that although it seems like a big deal to have something leaking in your yard, maybe half of all sprinkler systems have leaks like yours. The good news is you are not paying for the water that is leaking, except for the electric that is used by the pump kicking on and repressurizing the main line.

Also, with the pressure tank the leak is probably not affecting the performance of the system- again because the pressure tank/pressure switch is compensating for the loss of pressure.

So I hate to say this,but it's not that big a deal. Unless it is something that is making a mess in your yard or causing property damage don't obsess over it. Keep an eye on your yard. Look for areas that seem wet for no reason. If there are any kind of irrigation valve buckets in your yard (and there most likely are, because usually they don't just bury the valves in the ground.), look for lids, usually green. Open them up and look for water.

The thing is the pressure drop is there, but to me it does not seem like a large drop, but you might want to kind of monitor how often the pump kicks on and get back to me with that.

Now I am assuming that the gauge you are looking at is AFTER THE CHECK VALVE. IF NOT DISREGARD EVERY THING I JUST SAID.. THAT IS INFO I NEED.

The leak will get worse over time, because the pump  will keep hammering it with water and possibly air. So in time you will find it. Let me know if anything new happens. JIM