Marty,

Find out what the head's flow rates are rated for under 40 to 60 psi. What is your pump design flow rate(gpm)for 60 psi. It could be a flow problem which becomes a pressure problem. Who designed your system? Is each zone balanced to use only 80% of the mainline's flow capacity(pump's) @ 60 psi? Aloha

Sprinkler pump starts out strong for about a minute then the pressure dies down to a trickle. It is a 1 hp pump. The pressure gauge reads 45psi. Thanks, Marty

Marty,

Sorry but you haven't given enough info to make a good guess at what might be wrong. A WAG would be your system is probably sucking air on the intake side or spewing air on the outlet side. Your tank may be leaking as well. You say you have 13 heads in 3 zones is that 4.33 heads per zone. Then you talk about a 4 zone area. Your answer restates you have a 1 hp pump but doesn't do much about the questions I asked. It is a little confusing from my end. Since you probably can't tell me the answers to my questions, I recommend hiring a jet pump specialist who can troubleshoot your problem. By the way, this is a frequent problem with jet pumps. Did you say you had a jet pump? I can't remember. Aloha