How to Fix a Running Toilet

Originally posted on Men's Journal | By Max Winters | Last updated Jun 10, 2024 8:57 AM ET

Is there anything more annoying than the sound of a toilet running long after it's been flushed? It's an auditory nuisance that can waste hundreds of gallons and make your water bills skyrocket. Some plumbing issues are best left to the experts but from time to time, a common toilet issue is an easy enough diagnosis and fix.

What causes a toilet to run?

Faulty Flapper: The flapper is a rubber seal located at the bottom of the toilet tank. It's attached to the flush valve. If it doesn't create a proper seal, water can continuously leak into the bowl.
Fill Valve Issues: The fill valve controls the water level in the toilet tank. It's usually on the left side of the tank, connected to the water supply line. If it's not adjusted correctly or is malfunctioning, you'll see water constantly flowing into the overflow tube (usually an open tube in the middle of the tank.)
Float Problems: The float, typically a ball or cup, regulates the water level in the tank. The float is attached to the fill valve or connected to the flush mechanism. If the float ball is damaged or the float arm is set too high, the tank may overflow and constantly replenish gallons of water per day.
Faulty Flush Handle: A broken or stuck flush handle (the knob or button you push to flush) can cause the flush mechanism to remain engaged, leading to continuous running.

Determining the Issue

Remove the Tank Lid: Lift the lid off the toilet tank and set it aside in a safe place.
Check the Flow of Water: Use a dry-erase marker to make a level mark at the water line. Leave and come back an hour later to see that the water level is dropping. This confirms the problem is between the toilet tank and the toilet bowl.
Observe the Flapper: Flush the toilet and see if the flapper seals flat. Check the flapper for mineral deposits from hard water. A dirty flapper won't close correctly. If it's worn out it will need to be replaced.
Check the Fill Valve: Listen for any sounds after the tank has filled. If you hear hissing, it could indicate a faulty fill valve. Additionally, check for any visible leaks or water pooling around the valve.
Inspect the Float Mechanism: Ensure the float rod moves freely and isn't stuck in a raised position. If the chain is too short, the excess water will keep filling the overflow tube. If you have excess chain (too long), the toilet will have a weak flush. If the float is damaged, it needs to be replaced.
Test the Flush Handle: Flush the toilet multiple times to see if the handle sticks or doesn't return to its original position.

How to Repair a Toilet That's Always Running

1. Replacing the Flapper Valve

Turn off the water supply to the toilet by shutting off the valve located near the base of the toilet.
Flush the toilet to drain the tank.
Disconnect the bad flapper from the flush valve by unhooking it from the pegs or chain.
Install the new rubber flapper according to the manufacturer's instructions. Make sure it creates a tight seal over the flush valve.

There are a lot of versions. If your local hardware store doesn't carry your model's replacement, try a universal flapper.

Turn the water supply back on and allow the tank to fill. Flush the toilet and check that the issue is resolved.

2. Adjusting the Fill Valve

Shut off the water supply to the toilet at the shut-off valve near the base.
Locate the adjustment screw or knob on the fill valve. This may be located on the top of the valve or along the side, depending on the model.
Adjust the screw or knob to raise or lower the water level in the tank. The proper water level is approximately one inch below the top of the overflow pipe.
Turn the water supply back on and allow the tank to fill completely. Test the flush to ensure the water level is adjusted correctly.

3. Fixing the Float

Shut off the water to the toilet at the water supply valve near the base of the toilet bowl.
Adjust the float level or replace it if damaged. For ball floats, adjust the screw on the float arm to change its height. For cup floats, adjust the clip or screw to raise or lower the float.
Ensure the float rod moves freely, that the float is at the correct level (1-2 inches below the top of the overflow tube) and doesn't interfere with other parts.
Turn the water supply back on and allow the tank to fill. Test the flush to ensure the water level is maintained properly and the issue is resolved.

4. Repairing the Flush Handle

Shut off the water supply to the toilet at the shut-off valve near the base of the toilet bowl.
Disconnect the flush lever or chain attached to the flush handle.
Inspect the handle for damage or obstruction. Clean or replace the handle if necessary.
Lubricate moving parts with silicone grease to ensure smooth operation.
Reattach the chain or lever to the flush mechanism and adjust its length if needed to ensure proper flushing action.
Turn water supply on, let the tank fill with fresh water, flush to test.