How to Fix a Free-Flowing Toilet

10. Replacing the Fill Valve

With an empty tank, disconnect the water supply pipe with pliers. You can now remove the fill valve by unscrewing the locknut and lifting it out. Follow the instructions for the new fill valve by inserting it into the tank and securing it with the locknut. Tighten the nut as much as possible by hand and then use pliers to turn the locknut a further half-turn. Take the hose on top of the fill valve and clip it onto the overflow tube. Reattach the water supply pipe and switch the water back on at the shutoff valve. Make any water level adjustments, replace the tank lid, and you’re done!

By following these few simple steps, your toilet should no longer free-flow. However, if replacing the fill valve has not solved the problem, then it’s probably time to call in an expert!