How do I fix a running toilet without calling a plumber?

Start by removing the tank lid and identifying the problem. Most running toilets are caused by one of two things: a faulty flapper or a misadjusted float. The flapper is the rubber seal at the bottom of the tank. If it's worn or warped, water leaks into the bowl constantly. Replacement flappers cost about $5 at any hardware store and simply hook onto the overflow tube and connect to the flush chain. If the flapper looks fine, check the float. If the water level is too high and spilling into the overflow tube, bend the float arm downward or adjust the float screw to lower the water level about an inch below the top of the overflow tube. Both fixes take under 15 minutes.