how to fix running toilet fill valve flapper US

Open porcelain toilet tank showing the internal fill valve, flapper, chain, and overflow tube assembly.

How to Fix a Running Toilet: Fill Valve, Flapper, and Chain Troubleshooting Guide

August 16, 202621 min read

Learn how to fix a running toilet caused by a faulty fill valve, warped flapper, or tangled chain. Follow this step-by-step diagnostic workflow to isolate leaks, calibrate water levels, replace worn components, and lower your water bill.