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How to Fix a Running Toilet

Check inside the toilet tank for a leaky flapper, bad fill valve, or overflow pipe at the wrong height.

Toilet-repairs-toilet-keeps-running how to replace toilet fill valveFamily Handyman
Fixing a running toilet is a lot easier than you might think. In this article, we'll show you how to identify and solve the problem. Don't be intimidated by the plumbing. The fixes are straightforward, even if you don't have any plumbing experience. So stop wasting water and fix the toilet!

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Video: How to Fix a Running Toilet

Toilet Repairs: Stop a running toilet

The mysteries of a running toilet can drive you nuts. Whether you hear water running constantly or cycling on and off, we’ll help you decipher the clues so you can stop most leaks. Hardware stores and home centers carry the toilet parts for almost all repairs. One cause of a toilet running is a flapper that doesn’t seal. If water from the tank seeps around the flapper and into the bowl, the flapper is probably shot. Test for a leaky flapper as shown in the photo below if the toilet keeps running.

To replace the flapper, first shut off the water supply valve under the toilet (or the main supply if the valve leaks!). Flush the toilet to drain out most of the water, and unhook the old flapper. Buy a new flapper of the same type and install it according to the instructions on the package. Hook the flapper chain onto the flush lever arm so there’s a little slack when the flapper is closed.

Toilet Troubleshooting: Test the Flapper

Toilet Troubleshooting: Test the FlapperFamily Handyman

Push down on the flapper with a stick when you hear the water running and listen for it to stop. If it stops, you know the flapper isn’t sealing properly. Replace it. Check the fill tube length and cut it back so it’s at least 1/2-in. above the water line.

Toilet Troubleshooting: Check the Fill Valve for a Leak

Toilet Troubleshooting: Check the Fill Valve for a Leak diagramFamily Handyman

Flush the toilet and look for a fill valve leak. Lift up on the toilet float arm when the tank is filling to see if the water stops. Bend or adjust the toilet float arm so the tank stops filling when the water level is 1/2- to 1-in. below the top of the overflow pipe. If the fill valve still leaks, replace it as shown in the next photo.

Toilet Troubleshooting: Remove the and Replace Old Toilet Fill Valve

Toilet Troubleshooting: Remove the and Replace Old Toilet Fill Valve diagramFamily Handyman

Turn off the water supply, flush the toilet, and sponge the remaining water from the tank. Disconnect the water supply line, unscrew the fill valve locknut and lift out the old fill valve.

Install the New Fill Valve

Install the New Fill Valve diagramFamily Handyman

Insert the new fill valve into the tank according to the instruction sheet and tighten the locknut a half turn past hand tight. If the fill valve is at its maximum height, but the overflow pipe is still higher than the critical level mark, shorten the overflow pipe with a hacksaw so it’s 1 in. lower than the critical level mark on the fill valve.

Connect the Fill Tube

connect fill tube running toiletFamily Handyman

Attach one end of the new fill tube to the fill valve nipple and the other to the enclosed angle adapter (shorten the tube to avoid kinks, if necessary). Clip the angle adapter onto the overflow pipe. Finish the installation by attaching the flapper chain to the flush lever as described above. Turn on the water and test flush the toilet.

Required Tools for this how to replace toilet fill valve Project

Have the necessary tools for this DIY toilet repairs project lined up before you start—you’ll save time and frustration.

  • Hacksaw
  • Pliers

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • May need new fill valve