Identify and Fix Common Toilet Leaks

Toilets account for the largest amount of indoor leaks. An undetected toilet leak could waste as much as 5 gallons of water per minute. The most common toilet leak is caused by a deteriorated flush valve (flapper) at the bottom of the toilet tank. If the flapper does not seat properly, water will leak into the toilet bowl. Often this leak will occur without being heard. A new toilet flapper is inexpensive and can be purchase at any home improvement center with easy to install instructions. Flappers deteriorate over time and are worsened by in-tank cleaning products. 

These step-by-step tips will help you fix / detect some common toilet leaks.

Solutions to fix flush valve leaks


  1. Remove the tank lid, then flush.
  2. After the flapper / tank ball drops and the tank refills, add several drops of dark food coloring.
  3. Wait at least 20 minutes.
  4. If any trace of color appears in the toilet bowl, there is a leak.

Replacing a float cup fill valve


  1. Adjust the height by twisting the shank in / out of the valve body.
  2. Position the valve in the tank.
  3. Turn on the water.
  4. Adjust the water level.

Replacing a float ball (ballcock) fill valve


  1. Check the height and adjust if necessary.
  2. Place the valve in the tank inlet hole, making sure the rod arm position allows proper movement of the float ball.
  3. Screw the rod arm into the valve arm; screw the float ball onto the rod arm.
  4. Turn on the water supply.

Replacing a flapper


  1. Align the flapper over the mounting ears on the flush valve.
  2. Connect the chain to the flush lever.
  3. Turn on the water; Check operation.
  4. Trim the excess chain.

Replacing a tank ball


  1. Slide the lower life wire through the upper lift wire, then through the guide arm on the overflow pipe.
  2. Thread the tank ball onto the lower lift wire.
  3. Align the tank ball over the drain seat, keeping the wire vertical.
  4. Check the operation to be sure the ball sits properly.

Replacing a flush valve


  1. Cut the new overflow pipe to match the height of the old pipe.
  2. Install the valve by tightening the lock nut ½ turn beyond hand tight.
  3. Slide the gasket onto the threaded end of the valve.
  4. Connect the flapper chain to the flush lever.
  5. Attach the refill tube to the overflow pipe.
  6. Reconnect the tank to the bowl.