[bikestuff]

If you had hot water before the O-ring replacement and now don't, I would concentrate on the shower end. You probably know this, but you may have a shower that has a cartridge in it that essentially does the same thing as the mixing valve. Do you have cartridge? I dont think there is a way to put it in backwards, but I do remember that there is a specific Rotation angle that you mount it at. What type of shower valve do you have?

cheers,
bill