I had 2 shower heads installed in my house and BOTH of them are producing heavy knocking sounds every time a sink is turned on. I emailed the company and they sent me 2 sets of check valves to install in the cartridge.
All knocking sounds have gone away!! Thanks for fixing this for me.
Update
I had 2 shower heads installed in my house and BOTH of them are producing heavy knocking sounds every time a sink is turned on. I emailed the company and they sent me 2 sets of check valves to install in the cartridge. All knocking sounds have gone away!! Thanks for fixing this for me.