Step 5 · Install New Cartridge and Reassemble Valve
Before inserting the new part, use a clean rag to wipe out the inside of the faucet's valve body, removing any mineral scale, grit, or old rubber fragments. Next, take the new faucet cartridge and apply a light, even coat of plumber's grease to all of its rubber O-rings. This lubrication helps protect the seals during installation and ensures a watertight fit. Carefully align the new cartridge with the faucet body, making sure any tabs or notches line up exactly as the old one did. Press it firmly into place. Hand-thread the retaining nut back on clockwise to prevent cross-threading, then use your pliers or wrench to give it a final quarter-turn to snug it up. Do not overtighten.