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How to Fix a Running Toilet

  • 30 min
  • Very easy
  • 8 steps
  • 4 tools
  • 2 parts
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The lid lifts off the tank onto a towel, then a hand turns the fill valve adjuster so the float drops below the top of the overflow tube.

Step 1 of 8 Check the water level in the tank

Short answer

Check the tank water level, the flapper chain, and then the flapper with food coloring, in that order. Replace the flapper if color seeps into the bowl. Replace the fill valve if it hisses or will not shut off.

Safety first

DIY friendly

Do these before step 1.

  • WARNINGCeramic tank lids are heavy and crack easily. Lift with both hands and set it on a towel on the floor.
  • WARNINGBefore you unhook or replace any part, shut off the water at the valve behind the toilet, then flush to empty the tank.
  • NOTICEWipe up spills right away. Wet tile is slippery.
  • NOTICEDo not put bleach or cleaner tablets in the tank. They damage rubber parts. Wash your hands when done.

Stop and call a pro or the dealer if

  • Water leaks from the supply valve, its pipe, or the base of the toilet.
  • The valve behind the toilet won't turn or won't shut the water off.
  • The tank or the flapper seat is cracked.
  • It still runs after a new flapper and fill valve.

Mechy's guides help, but they don't replace the maker's manual, your training or your site's rules. If something doesn't match what you see, stop and check.

Tools

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Parts and supplies

  • 1×Toilet flapper (the rubber stopper at the tank bottom)2 in or 3 in; match the old one (size is on it or measure the drain)Check before you buy
  • 1×Toilet fill valve (only if it hisses or won't shut off)Universal fill valve; check the package for your tankCheck before you buy

Steps

  1. The lid lifts off the tank onto a towel, then a hand turns the fill valve adjuster so the float drops below the top of the overflow tube.

    Step 1 of 8

    Check the water level in the tank

    Lift the lid with both hands and set it on a towel. If water spills into the open pipe in the middle (the overflow tube), the level is too high. Turn the adjuster on the fill valve (the tall part with the float) to lower the float. Flush and recheck.

    Old towel or rag, Flat screwdriver

  2. A hand moves the chain clip to a farther link so the chain hangs with a small loop of slack above the flapper.

    Step 2 of 8

    Check the flapper chain for slack

    The chain links the flush handle arm to the flapper. It needs about 1/2 in of slack (one or two links) when the flapper is closed. If it's tight, hook it on a link farther from the arm. If it's caught under the flapper, free it.

    A chain that is too long can slip under the flapper and hold it open.

  3. Drops of colored dye fall into the tank water, then a color streak seeps from under the flapper toward the bowl.

    Step 3 of 8

    Test the flapper with food coloring

    Put a few drops of food coloring in the tank. Don't flush. Wait about 15 minutes. If color shows in the bowl, the flapper leaks: go on to step 4. If the bowl stays clear, the flapper is fine: skip to step 8. Flush after to clear the dye.

    Food coloring

  4. A hand turns the supply valve clockwise, then the handle is pressed and the tank water level drops to the bottom.

    Step 4 of 8

    Shut off the water and empty the tank

    Turn the small valve on the wall or floor behind the toilet clockwise until it stops. Flush and hold the handle down. If the tank refills, the valve is not sealing: stop. Sponge out what's left so the flapper area is nearly dry.

    Small bucket or sponge

  5. The flapper's loops slide off the pegs, and a rag wipes in a circle around the drain opening.

    Step 5 of 8

    Remove the old flapper and clean the seat

    Note which chain link was used. Unhook the chain from the handle arm. Slip the flapper's two side loops off the small pegs on the overflow tube. Wipe the round rim under it (the valve seat) with a rag until smooth. Gunk there causes leaks.

    Old towel or rag

  6. The new flapper's loops snap onto the pegs and its chain clips to the arm with a small loop of slack.

    Step 6 of 8

    Fit the new flapper and set the chain

    Use the same size as the old one (2 in or 3 in, printed on it). Hook its loops over the pegs, then clip the chain to the handle arm with about 1/2 in of slack (one or two links). The flapper must drop flat over the opening.

  7. A hand turns the supply valve counterclockwise, the tank fills, and the water rises to the marked line and stops.

    Step 7 of 8

    Turn water on and set the level

    Turn the valve counterclockwise to open it. Let the tank fill to the line marked inside the tank, or below the top of the overflow tube. Adjust the float if needed, then flush and watch it stop. Check for leaks at the valve.

    Flat screwdriver

  8. A hand lifts out the old fill valve and sets the new one in the tank.

    Step 8 of 8

    Replace the fill valve if it hisses or won't stop

    If the fill valve hisses or the tank never stops filling after the level is set, replace it. Shut off the water, empty the tank, and follow the directions on the new valve's package. Then repeat step 7.

Common mistakes

  • Buying the wrong flapper size instead of matching the old one.
  • Leaving the chain too tight or so long it gets caught under the flapper.
  • Skipping the wipe of the valve seat before fitting the new flapper.
  • Setting the water level above the top of the overflow tube.
  • Forgetting to shut off the water before removing parts.

Questions

Why does my toilet keep running?

Most often the flapper leaks, the chain is too tight or caught, or the water level is too high. A worn fill valve can also keep water running.

How do I know if the flapper is leaking?

Put a few drops of food coloring in the tank without flushing. If color shows in the bowl after about 15 minutes, the flapper leaks.

How much slack should the flapper chain have?

About 1/2 in, one or two links, when the flapper is closed. Too tight keeps it open; too loose can get caught under it.

What size flapper do I need?

Usually 2 in or 3 in. Match your old flapper, or measure the drain opening, and take the old one to the store.

When should I replace the fill valve?

Replace it if it hisses or the tank won't stop filling even after the water level is set correctly and the flapper seals.

Sources

  1. Constantly Running Toilet: Common Causes and Solutions, Fluidmaster
  2. How to Fix a Running Toilet, Korky

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