ASV Rattling -- I'm perplexed

[cocylist]

I installed my irrigation system about 3 years ago. Ever since installing it, I have one zone that causes the ASV to rattle pretty loud. All other 4 zones are totally quiet when running. I've replaced the valve, flushed the system, checked for leaks and I just can't seem to figure out what in this zone would cause the rattling. Irrigation is after our PRV which is set at 70psi. All spray bodies are Rainbird SAM PRS 30 (check valve/pressure regulated at 30psi) with Toro Precision spray nozzles. There are 6 heads in this zone.

My understanding is that this is usually a sign of a high flow situation, but I've walked where the lines are and I haven't notice any significantly soft/mushy areas so I struggle to think it's leak related.

Any suggestions on additional steps I can take to troubleshoot this? Thank you!

 

[cocylist]

Update: Yesterday I cranked down the arc screws on the spray heads to the point of turning off the flow completely. I let the zone run like that for 2 hours. Water meter wasn't moving at all and as no wet spots in the yard. So that should rule out a leak.

 

[Sponsor]

 

[Smooky]

How many spray heads are in the other zones and do they put out the same amount of water?

 

[cocylist]

The other front zone has 7 heads w/ Toro Precision Rotary nozzles..so that zone puts out less w/ a percip rate of .6"/hr. The zone that's rattling previously had all mp rotators on it which are much lower precip rate (.4?) than what I have on there now. Same rattling with the MP Rotator as with the higher output Toro Precision nozzles.

Back zones are rotors w/ 5 rotors on each zone.