I decided to gut the bathroom of an older rent house that i have and have gotten myself in a little bind. As of now i am on my second shower valve. The first one was a moen turn lever with the 4 - 1/2' outlets, now i followed all instructions hot left cold right shower pipe on top and bath spout on bottom. I thought i had done a great job until i cut the water back on and gave it a test run. absolutely nothing happened when i turned the valve no water no air nothing. Now i know for a fact water was getting to it and nothing was clogged because i eventual cut the pipe and water started leaking also when i removed the cartridge water would start to come out. So i thought the valve was messed up so i packed everything up and got another this one is an american standard. basically the same thing has happened after install, when i start to unscrew the cartridge water starts leaking every where but as soon as i screw it back water has no flow. Now im sure there is a simple solution but i have honestly tried everything to my knowledge without calling a plumber. Do i need some sort of vent to make the water flow is ther some sort of hidden plug that could be plugging it. sorry for rambling... please help.
Given that this has happened on two valves, are you sure you've got BOTH the hot and the cold water turned on? Those are pressure balanced valves and if one line be it hot OR cold is off the valve wont work. So.....say for instance you've got the valve to your water heater turned off for some reason.....your shower valve isnt going to work.