[widebody911]

I recently replaced all of my sprinkler valves. The old ones were leaking/not working, and the whole thing was a mess. I ripped everything out and started over with all new stuff. I even installed a cool new digital timer.

Everything works great except for the pipes "slam" badly when the valves turn on or off. I've mitigated the problem somewhat by turning down the supply valve. It still rattles the pipes, but not as bad. I'm pretty sure the noise is the pipes banging against the joists where the straps are loose.

The system is divided into two sets of 3 valves. Interestingly, after I completed the first set of 3 valves and ran it for a week, I didn't notice any hammering. It wasn't until I set up the valves in the back yard that the problem started.

I'm wondering if there was some technical detail I got wrong or left out. I'm using lower-end RainBird valves, 3/4" Sch 40 PVC pipe from the house all the way through to where it connects to the existing 3/4" Sch 20 pipes in the ground.

Any other ideas or possible solutions?