You might need an adjustable wrench or basin wrench for stubborn nuts under the sink. Depending on your faucet, a set of Allen wrenches (hex keys) may be required to remove the handle, and some cartridges require a specialized removal tool. Penetrating oil can also be useful for seized parts.

The absolute first step is to completely turn off the hot and cold water supply lines leading to the faucet, usually found under the sink. Then, open the faucet to drain any remaining water from the lines and relieve pressure. This prevents accidental floods and makes the repair safer.

Corroded or seized parts can be difficult to remove, especially if the faucet is old, potentially adding significant time. Identifying the correct replacement part can also cause delays if the brand or model is obscure. Tight spaces under the sink can make access challenging.

First, double-check that the new cartridge is fully seated and properly aligned according to any notches or keys, as incorrect alignment is a common cause of leaks. Ensure all retaining nuts or screws are snug, but do not overtighten. If the issue persists, inspect the cartridge for any defects or verify it's the exact correct model for your faucet.