What to Do When the Toilet Won't Stop Running

If your toilet is losing water, the problem can usually be quickly identified by taking a look inside the tank.

Under the tank's lid, you'll see a few items:

  • The float - a plastic ball at the end of an arm
  • The flapper - a plug at the bottom of the tank at the end of a chain
  • The pump
  • The overflow tube

To understand what could be going awry in your toilet, it's best to first know what happens with each of these items. When you flush the toilet, the handle pulls on a lever attached to the flapper's chain. The flapper then lifts up and lets the fresh water in the tank flow into the bowl.

Check out the tank to determine the cause of  your running toilet.If your toilet's running, it's time to take a look inside the tank.

As the water drains, the float drops to the bottom of the tank, which triggers another lever. This lever turns on the pump, and begins to fill the tank up with fresh water. The pump is turned off when the float reaches the top of the tank again. The water should not go past the top of the overflow tube.

1. Check the flapper.

An old or damaged flapper is one of the most likely culprits behind a running toilet. The flapper needs to create a tight seal so water doesn't leak down into the bowl. If water is slowly seeping past the plug, the float will eventually be lowered enough to trigger the pump to turn on.

To replace the flapper:

  • Turn off the water to your toilet - use the silver knob on the wall behind the toilet. Flush the toilet to empty the tank.
  • Remove the rubber flapper from the tank and bring it to the hardware store.
  • Attach the new flapper to the chain, ensuring that it's long enough to effectively plug the tank but not so long that you need to jiggle the handle to get it in place.

Flappers are generally pretty universal, so the biggest thing you'll need to take note of is the size. Older toilets generally have a 2-inch outlet valve diameter, while newer ones more likely have a 3-inch outlet valve diameter.

2. Check the float.

The resting place of your float is key here. If the float naturally rises above the overflow tube, the pump won't turn off until the water reaches that position. Then, water will go down the overflow tube, lowering the water level in the tank, starting the process over again. To solve this, simply readjust the rod so the float's resting place is below the overflow tube.

3. Check the chain.

When the toilet isn't being flushed, the chain leading to the flapper shouldn't be too tight. This could be lifting the flapper enough to let water through. Check the flapper position and the chain and adjust as needed so the flapper shuts tight.