I have a 8 zone sprinkler system. It is ran off of my drilled well. I have a submersible pump. My pressure switch has a cut-in of 40psi and a cut off of 60psi. Noticed lately that my rainbird 5004's arent spraying out as far as normal. Looked at pressure gauge by my pressure tank and it said 30psi. Watched zone by zone and this is what i see. The first zone sprays at 40 or 41psi. as soon as the zone ends and the next one starts- pressure drops to 23psi and only comes back up to 30psi. doesn't matter what zone you start with . Sometimes it will go on to the next zone and not lose pressure. You can run the first zone forever and not lose pressure.