I have a customer who put in a pool and the pool people used SRVs (cr-ppy valve our nickname for SRV is sh-tty residential valve) for the system. They are manifolded off a 1" tee about 3' apart in 6" VBs facing opposite directions. When one is turned on then off they go through this bizarre thumping back and forth sometime for up to 5 minutes causing water to pulse from the heads. The plastic on the bonnet can be seen going up and down. I got an upgrade with flow controls and I'm going to switch out the guts and bonnet to see if this fixes the issue. Anybody else had this problem?