I am trying to replace my shower handle, faucet, and shower head. I cant get the valve stem off. There is a black plastic cover over it but behind the shower wall. I dont know if I should break the old one (since there is no way it is gonna come through) or if I should cut the hole bigger in the shower wall. Any ideas or suggestions. It looks like the hole should have been 6 inches but it is not.

 

Is this a tiled shower or a surround or unit? How are you getting to the water pipes to remove them? Surely they are not accessible from inside the shower.
Can you open up the wall behind the shower valve and access everything from there? Say the shower and bedroom are beside one another, go through the bedroom wall to get to the backside of the shower valve. If it is just cement board and tile in the shower then make a bigger hole to get everything out. But remember you have to replace the tile to the size it was before and make it match and be water tight. Might be easier to repair the backside of the wall. Make sure the valve is firmly attatched to something besides the pipes when you install the new one.

 

It is a common practice for installers to tile and/or mount surrounds around stems with openings just large enough for the part of the stem the handle fits on to fit through to protect from leakage etc.You may have no choice but to enlarge the holes.I'm assuming you are replacing the entire assembly and not trying to just replace what shows like the handles etc.

Accessing from behind the unit will be necessary to replace the entire assembly and assuming no part of the exterior parts is larger than the holes it has to go through you may be able to solve your problem that way.Usually there is an acess panel already there but if not there should be and it usually isn't that hard to make one.

If all you are replacing is the "cosmetic" parts such as handles etc know that handles especially are not "standardized" as far as sizing is concerned.Heads and spouts are more easily replaced but handles can be a multitude of sizes and you'll need to match yours up to a replacement.Some so called universals exist but they aren't that great and only work for some situations.

If you intend to keep the faucet assembly and only replace the stems you may need a tool set known as a "plumbers socket set" to remove them.Stems come in many sizes and usually have bushings or similar parts behind the wall that require a deep socket to reach.This set is specific for that purpose.You will likely need to enlarge the holes the stems pass through.