How Do You Fix a Running Toilet?

Most running toilets can be fixed in under an hour with inexpensive parts and no special skills. The usual culprits are a worn or warped flapper that lets water leak into the bowl, a float set too high so water spills into the overflow tube, or a lift chain that is too tight or tangled. Start by lifting the tank lid and watching what happens after a flush. Once you spot where the water is going, the fix is usually a simple adjustment or a part swap.

A running toilet is more than an annoying sound. It can waste a surprising amount of water and quietly raise your utility bill, so it is worth fixing promptly.

How a toilet tank works

Understanding the basic parts makes troubleshooting much easier. Inside the tank you will typically find:

• The flush handle and lift chain, which pull up the flapper when you flush.
• The flapper, a rubber seal at the bottom of the tank that opens to release water into the bowl and closes to let the tank refill.
• The fill valve, usually on the left side, which lets fresh water into the tank.
• The float, a ball or cup attached to the fill valve that rises with the water and shuts the valve off at the right level.
• The overflow tube, a vertical pipe in the middle that sends excess water into the bowl to prevent the tank from overflowing.

When everything works, the flapper seals tightly, the tank refills to the right level and the fill valve shuts off. A running toilet means one of these steps is not happening.

Step 1: Find the source of the problem

Remove the tank lid and set it somewhere safe, since it is heavy and breakable. Then watch closely.

Is water flowing into the overflow tube?

If water is spilling over the top of the overflow tube, the water level is too high. The problem is likely the float or fill valve.

Is the water level below the overflow tube?

If the tank fills to a normal level but the toilet still runs or refills on its own every so often, water is probably leaking past the flapper into the bowl.

Try the food coloring test

Add a few drops of food coloring to the tank water and wait about 15 to 30 minutes without flushing. If colored water appears in the bowl, the flapper is leaking. Flush afterward so the coloring does not stain.

Step 2: Check the lift chain

The chain connects the flush handle to the flapper.

• Too tight: the flapper cannot close fully, so water keeps running.
• Too loose: the flapper may not lift enough for a full flush, or the extra chain can get caught under the flapper.
• Tangled: a kinked chain can hold the flapper open.

Adjust the chain so there is just a little slack, often about half an inch, when the flapper is closed. Many chains have a clip that lets you move to a different link.

Step 3: Inspect and replace the flapper

Flappers are made of rubber and wear out over time. Minerals in water and cleaning products in the tank can make them stiff, warped or brittle.

Check it

Turn off the water supply valve behind the toilet and flush to drain the tank. Feel the flapper. If it is hard, cracked, misshapen or slimy, it is likely not sealing well. Also check the valve seat, the ring the flapper rests on, for buildup or roughness.

Clean it

Sometimes cleaning the flapper and valve seat with a soft scrub pad is enough to restore a good seal.

Replace it

If cleaning does not help, replace the flapper:

1. Turn off the water and drain the tank.
2. Unhook the old flapper from the pegs on the overflow tube or slide it off the tube.
3. Disconnect the chain from the handle arm.
4. Take the old flapper to a hardware store to match the size and style, or check your toilet model.
5. Attach the new flapper, connect the chain with a little slack and turn the water back on.
6. Test with several flushes.

Step 4: Adjust the float

If water is running into the overflow tube, lower the water level by adjusting the float.

• Ball floats sit on a metal or plastic arm. Gently bend the arm down slightly, or turn the adjustment screw on top of the fill valve, so the ball sits lower.
• Cup floats slide up and down along the fill valve. Squeeze the clip or turn the adjustment rod to move the float down.

Aim for a water level about an inch below the top of the overflow tube. Many tanks have a marked fill line.

Step 5: Check the fill valve

If adjusting the float does not stop the water, the fill valve itself may be worn. Signs include:

• Hissing or constant trickling even when the water level is correct.
• The tank filling very slowly.
• Water continuing to flow even when you lift the float by hand.

Sometimes debris inside the valve causes trouble, and flushing it out helps. If not, a replacement fill valve is inexpensive and comes with instructions. It involves shutting off the water, disconnecting the supply line, removing the old valve, installing the new one at the right height and reconnecting.

Step 6: Check the refill tube

A small flexible tube runs from the fill valve to the overflow tube and refills the bowl after each flush. If it is pushed too far down into the overflow tube, it can siphon water continuously. Make sure it is clipped to the top of the overflow tube rather than inserted deep inside.

Tools and supplies to have on hand

• A replacement flapper that fits your toilet.
• A universal fill valve kit, if needed.
• A sponge and bucket to remove leftover water.
• Rubber gloves.
• An adjustable wrench for supply line connections.
• Towels to protect the floor.

When to call a plumber

Most running toilet repairs are straightforward, but consider professional help if:

• The toilet still runs after replacing the flapper and fill valve.
• Water is leaking around the base of the toilet or onto the floor.
• The tank itself is cracked.
• The shutoff valve is stuck or leaking.
• You are not comfortable working on plumbing connections.

The bottom line

A running toilet usually comes down to one of a few simple parts: the chain, the flapper, the float or the fill valve. Watch what happens inside the tank, test the flapper with food coloring, make small adjustments first and replace worn parts as needed. Fixing it promptly stops the noise and keeps water from going down the drain unnoticed.