I have an American Standard (colony, I believe) shower control valve. It has two oval-type seals and one round seal in the cartridge. My shower head has been dripping very slowly for a couple months now. I replaced the cartridge as I thought this would be the fix but I still have the dripping, which never stops now. Could it be the manifold or pressure controller inside the manifold? I really do not want to replace the manifold as this would mean tearing out my tile on the wall. Any advice would be appreciated. Thanks

The new cartridge should have fixed it. I would remove the new cartridge, put my finger inside the body of the faucet and feel for imperfections. Also, lubricate washer before you slide new cartridge in so you don't clip the O ring. Reinstall and see if it helped..

Thanks for the response Milo. I don't have a faucet to put my finger in. Not sure I understand. I have a single handle controller for my shower head. I do not have a tub combo. I remove the valve/cartridge and all I can see is a manifold with a pressure controller inside it. The cartridge has seals in it that seal up against a smooth surface of the manifold. I can feel that area and it feels fine/smooth.

Ok, if the interior of the faucet body appears to be smooth and without imperfections that check out the seals attached to the cartridge. Any smallest dent or nip will cause water to pass through and into your shower.

On top of Milo's advice I will suggest to remove the cartridge, puls the water for a second to flush out any dirt from the valve, clean/ lubricate and install the cartridge.

Thanks.
John

Thank you both very much for the advice. Tried the flushing but still have the dripping. Called a plumber out and he is now suggesting replacement of the rough in manifold/housing? or the pressure control unit. Hopefully not the rough in. A LOT of tile on both sides of wall. Thanks again gentlemen. I appreciate it.