So we bought this home, and the guest shower was stuck. heavy calcium buildup because former owners did not use any kind of softener. Anywho, replaced the cartridge on this older moen shower valve and only hot water.. this valve has only the 1200/1225 cartridge and two small stop valves on each side and that is it. The one thing I have not done is to remove the stop valve on either side. Maybe the cold is crumbed up? Anyone?
They are there so you can replace the cartridge without shutting off the whole house supply and without having an access panel on the other side of the wall. They should be 1/4 turn valves.