I just bought a house that has a well water system which has worked fine inside the home. The house had a sprinkler system already installed. Recently I turned on the sprinkler system and was dismayed at what appears to be low pressure - the sprinkler heads (Hunter rain-bird popups) cover maybe 20' radius at best. There is a large pressure tank in garage which with no water running is typically at about 60 lbs on the gauge. When I turn on the sprinkler system, I can hear the pump comes on almost immediately but the pressure drops to about 30-35 lbs over about a 2 minute time period and I can see a noticeable reduction in "strength" from the sprinkler heads. If I turn the system off, the pressure recovers in the tank in maybe a minute or two. There was no information on the well from the previous owner, so I don't know anything about type of pump or depth of the well. The sprinkler system was installed with 3/4" PVC pipe (at least the portion I dug up replacing a broken line). There are generally 6-8 heads on each zone.

I bought a pressure gauge and put it on the end of a hose and get about 35 psi, so there seems to be a considerable pressure drop between pressure tank and hose bib even when the sprinkler is not running.

The neighbors sprinkler systems seem to have much high pressure and much better coverage with their sprinkler systems and they all have similar vintage homes on wells.

Any suggestions as to where to start trouble shooting would be much appreciated. I asked a plumber who was out at the house recently and he just kind of shrugged his shoulders.