To replace a Pfister cartridge, start by turning off the water supply and opening the faucet to drain out any remaining water. Remove the handle, valve adapter and cartridge. Slot in the new cartridge, and tighten it with pliers.
Tools needed to replace a Pfister cartridge include adjustable pliers, a screw driver and the replacement cartridge. Ensure the replacement cartridge is suitable for your faucet's model. If you're unsure, carry the old cartridge with you to the hardware store when buying the new cartridge.
Start by turning off the water supply to prevent any water damage while replacing the cartridge. Often, the valves for turning off the water supply are under the sink. Switch them to the off position to isolate water supply to the faucet. Open the faucet to drain all the remaining water and release faucet pressure.
Remove the handle. Depending on the model, you may remove the screws using a screwdriver or turn the hub counterclockwise to unscrew it. Remove the valve adapter by turning it counterclockwise. Unscrew the hex nut using adjustable pliers. Remove the old cartridge, and replace it with the new one. Tighten the hex nut with adjustable pliers. Return the adapter, and tighten it by screwing it by hand. Complete the installation process by replacing the faucet trim.