Step 5 · Clean Valve and Install New Cartridge

This is the step people usually slow down on. Go finger-tight first, then a quarter turn. No rush — replay the clip whenever it helps.

With the old cartridge removed, use a rag to wipe out the inside of the brass valve body. Remove any mineral deposits, sediment, or bits of old rubber gasket. A small nylon brush can help with stubborn deposits. Take your new replacement cartridge and apply a thin, even layer of plumber's grease to all of the rubber O-rings and seals. This lubrication is crucial for a smooth installation and a watertight seal. Carefully align the new cartridge with the valve body—most cartridges have markings like 'HC' (Hot/Cold) that must be facing up. Slide the new cartridge straight in until it is fully seated. For Moen, re-insert the retaining clip from the top until it clicks securely into place. For Delta, thread the bonnet nut back on by hand first to avoid cross-threading, then tighten it with channel-lock pliers until it is snug. Do not overtighten.