A running toilet can waste hundreds of gallons per week. Most are caused by one of three simple parts and fixable in under 30 minutes.
STEP 1: Diagnose the Problem
Remove the tank lid and listen carefully. A hissing sound usually means the fill valve is running. Water trickling into the bowl means the flapper is leaking. Confirm the flapper by adding a few drops of food coloring to the tank if color appears in the bowl within 5 minutes without flushing, replace the flapper first.
STEP 2: Replace the Flapper
Turn off the water supply valve at the base of the toilet, then flush to empty the tank. Unhook the old flapper from the pegs on either side of the flush valve and slip the chain off the handle arm. Snap the new flapper onto the pegs and attach the chain with about half an inch of slack.
STEP 3: Adjust or Replace the Float
If water is too high and spilling into the overflow tube, the float needs adjusting. On a cup float, pinch the adjustment clip and slide it down the fill valve shaft. The water level should sit about one inch below the top of the overflow tube.
STEP 4: Replace the Fill Valve If Needed
If adjusting the float does not stop the running, the fill valve needs replacing. Turn off water, flush, sponge out remaining water, disconnect the supply line, unscrew the locknut under the tank, pull out the old valve, and install the new one per the kit instructions.
STEP 5: Test and Confirm the Fix
Flush several times and watch the tank refill each time. Water should stop running within 30-60 seconds of the tank reaching full. If it still runs, check that the flapper chain is not kinked, twisted, or pulled too tight.
PRO TIP
Take a photo of your toilet’s model number stamped inside the tank before shopping for parts to ensure compatibility. Toilet repair kits that include a flapper, fill valve, and float together are often cheaper than buying each part separately.
SUPPLIES NEEDED
Adjustable pliers
Replacement flapper match to your toilet model
Fill valve replacement kit if needed
Float cup if needed
Rubber gloves
Towel or small bucket