Today we’ve been called out here because of previous work that was done to the shower in the hallway bathroom is not delivering hot water but more lukewarm water. I replaced the original shower cartridge because of drippy showerhead, which indicated that the cartridge was going bad and failed prematurely on my previous visit. I took out the cartridge I had put in and put another new cartridge in there and was still getting the same results. I took the same cartridge and flipped the positioning of the cartridge and was now getting hot water, which indicates that the supply lines that are inside of the wall are connected to the shower valve incorrectly. Where the waterlines are currently inside the wall the cold lines is connecting to the hot inlet port, and the hot lines is connected to the inlet port. This is why it is mixing hot and cold water and to correct it would be to opening the wall and rerouting the supply lines that are connecting to the shower valve. I recommend doing that o