I was ready to install the shower head and valve cover. It seemed it was long ago that the rough plumbing was done. No leaks to date. Before I started, I turned on the valve. No leaks by the shower head. However, when I shut it off, the valve started leaking again. I tightened down the valve screws without success. I ran down to the basement and shut off the water. I ran back up the stairs as I yelled to my wife, Efiwym that the water was off. I removed the valve cartridge and check for a possible crack. I looked closely at the valve body. Nothing there. I put the cartridge back in. Down to the basement. Up the stairs. Still leaking. Tightening the screws did not help. I went back downstairs and shut off the water. I was back in the master bathroom and I removed the cartridge.
I took the cartridge with me to the home improvement store where I bought the shower faucet. I talked with a sales associate about my problem. He walked to another aisle and found a replacement cartridge. He took it out of its sealed package and compared them. Looks like a match. He put it back in the opened packaged and handed to me. He said we were good. I said thanks and headed home.
I went straight to the master bathroom to install the cartridge. I installed the cartridge and returned to the basement to turn on the water. I ran back upstairs to check for leaks. No leaks, at least for now. I surmised that I cracked the cartridge when I turned the shower with the shower head pipe capped. The back pressure of the water might have been too much. I was not going to make that mistake again. I remove the galvanized pipe and installed the brushed nickel pipe and shower head. Time for a test. Success! However, without a shower door, I had water all over the floor. I placed the cover on the shower valve, and I was done with the plumbing finally. Finishing the drywall was next.