My home irrigation system has been working fine since we re-installed it (have an old pump, well and tank but new controller, lines, sprayheads, etc.). I noticed the other day that when I ran a garden house from a spigot hooked to the well, that my tank emptied and the tank pressure dropped to zero. The pump never came on to refill the tank. The next morning, I noticed that the storage tank was full with plenty of pressure. I tried it two days in a row with the same results.

Interestingly, the irrigation system itself seems to work fine, as far as I can tell, although I haven't really sat down and watch it run for sevreal hours at a time, so I could be wrong about this.

I called a local well service company. They suggested that I may have dirt or cobwebs in the pressure switch and that I could easily clean it out myself. This sounds like a good place to start, but I don't know what a pressure switch looks like! Can anyone give me some help identifying what one looks like and what needs to be cleaned?

Any other ideas as to what might be wrong?

Thanks in advance.