Step 5 · Clean Valve and Install New Cartridge
Inspect the inside of the brass valve body for any rubber debris or mineral deposits. Clean it out with a clean rag wrapped around your finger or a small bottle brush. Take the new Moen 1222 cartridge and apply a light coating of the included plumber's grease (or silicone grease) to all the rubber O-rings. This is crucial for easy installation and a proper seal. Align the new cartridge with the 'H/C' (Hot/Cold) markings facing up, matching the orientation of the old one. Push the new cartridge firmly and evenly into the valve body until it is fully seated.