You will primarily need a new toilet flapper that is compatible with your toilet model, a sponge, and a towel for cleanup. While often not required, an adjustable wrench can be helpful if you need to disconnect or secure the water supply line to the fill valve. Always ensure your replacement flapper matches the size and style of your existing one for the best seal.

The most crucial safety step is to completely shut off the water supply to the toilet before you begin to prevent accidental leaks or flooding. Be cautious when turning the water supply back on not to overtighten connections, as this can damage parts and create new leaks. Always work in a well-lit area to avoid slipping on any spilled water.

Replacing a toilet flapper is considered a beginner-level DIY project and is generally very straightforward. It typically takes most people between 15 to 30 minutes from start to finish. The cost is usually just for the flapper itself, which is an inexpensive part.

A common mistake is selecting the wrong size or type of flapper for your toilet, which will prevent a proper seal. Ensure the flapper chain has the correct amount of slack; too tight, and it won't seal, too loose, and it can get caught. If your toilet is still running after replacement, check that the flapper is seated correctly on the flush valve and that the chain isn't obstructing it.