Step 5 · Clean Valve Body and Install New Cartridge
Once the old cartridge is out, inspect the inside of the brass valve body. Use a rag and a small brush (an old toothbrush works well) to clean out any mineral deposits, debris, or pieces of old rubber seals. The inside surface must be clean and smooth for the new cartridge to seal properly. Take your new cartridge and apply a thin layer of the included plumber's grease (silicone grease) to all the rubber O-rings. This lubricates them and helps ensure a watertight seal. Align the new cartridge with the 'H/C' marking facing up, just as the old one was oriented. Push the new cartridge firmly and evenly into the valve body until it is fully seated. It should slide in until its flange is flush with the front of the valve body.