How to Fix a Running Toilet: The 4 Most Common Fixes

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How to Fix a Running Toilet (Fast & Easy)

A running toilet is annoying and costs you money — sometimes hundreds per year in wasted water. The good news? Almost every running toilet can be fixed in just a few minutes with very simple adjustments.

Here are the four most common causes and exactly how to fix each one.

1. The Flapper Isn’t Sealing (Most Common Issue)

The flapper is the rubber seal inside your toilet tank. When it gets worn, dirty, or misaligned, water leaks from the tank into the bowl — making your toilet run nonstop.

How to check:

  1. Remove the tank lid.
  2. Look at the rubber flapper at the bottom.
  3. If it’s not fully covering the drain opening, that’s the problem.

How to fix it:

  • Clean it: Wipe the underside of the flapper and the drain seat.
  • Adjust the chain: If the chain is too tight, the flapper can’t close.
    • There should be ½ inch of slack.
  • Replace it: If it’s warped, cracked, or stiff, replace it.
    • Cost: $5–$10 at any hardware store.
    • Install: Unhook old one → hook on new one → adjust chain.

This alone fixes 70% of running toilets.

2. The Float Is Set Too High

The float controls how much water fills the tank.
If it’s set too high, the tank overfills, the water spills into the overflow tube, and the toilet keeps running.

How to check:

Look at the overflow pipe inside the tank.
If water is constantly draining into it → the float is too high.

How to fix:

There are two types of floats:

A. Screw Type (most common)

On the fill valve you’ll see a screw.

  • Turn it clockwise to lower the water level.

B. Sliding Clip Type

Some floats slide on a metal rod.

  • Pinch the clip and slide the float down ½ inch.

You want the water level to sit 1 inch below the top of the overflow pipe.

3. The Fill Valve Is Worn or Dirty

If adjusting the float doesn’t help, the fill valve may be failing.

Symptoms:

  • Toilet hisses
  • Water keeps trickling
  • Water refills randomly

How to fix it:

  1. Turn off the water supply (valve under the toilet).
  2. Remove the fill valve cap (twist counterclockwise).
  3. Look for debris or mineral buildup.
  4. Rinse the inside.
  5. Turn the water back on for 2 seconds to flush it.
  6. Reinstall cap.

If that doesn’t fix it → replace it.
Fill valve kits cost $10–$20 and take 10 minutes to install.

4. The Overflow Tube Is Cracked or Too Short

This is less common, but if the overflow tube inside the tank is cracked or damaged, water will constantly leak into the bowl.

How to check:

  • Shine a flashlight on the overflow tube.
  • Look for cracks, splits, or water flowing out the side.

Fix:

You’ll need to replace the entire flush valve assembly — but don’t panic.
This still only costs $20–$25 and takes about 30 minutes.

When to Call a Plumber

Call for help if:

  • Water leaks from the base of the toilet
  • You see cracks in the tank
  • Adjustments don’t stop the running
  • You hear gurgling sounds from other drains

These can indicate deeper plumbing issues.

Quick Maintenance Tips

These help prevent future running-toilet problems:

  • Clean your flapper every few months
  • Replace the flapper every 1–2 years
  • Keep water level 1 inch below overflow
  • Avoid jiggling the handle — fix the chain instead

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