After a master bathroom remodel (new shower tiles and valves), every time the toilet flush or any faucet within 50 feet closes, there's a knocking sound from wall and ceiling with the shower. The piping is CPVC and PEX just at the shower. I tried a small hammer arrestor at the toilet and faucet and it didn't do anything. Next I opened up the wall behind the shower. The pipes were a little loose since they're retrofit. But securing them didn't help the knocking. I added 3/4" Sharkbite arrester (sized for 12-32 unit), the hammering stopped for a day, then came back the next day. I have city water and I next checked the pressure - 50 psi - not too high. I don't have an expansion tank on the water heater since it's an old house, but I didn't even turn on the hot water yet. I'm getting desperate, I added some air chambers (3ft x 3/4") in the attic space 30 feet upstream of the bathroom - no change in the knocking. I opened up a bigger hole in the wall behind the shower and added more air chambers (3/4 x 30"). This stopped the knocking for a week. I was excited, but then it came back. I drain all the water to refill the air chambers. It stopped the knocking, but this time only for a day. I'm about to add more arrestors, but it can't be right. Anywhere else in the house, I might have given up and lived with it, but this wall is in the master bedroom. Anyone experience anything like this before?