UsefulHow
Every useful fix starts with knowing how.

How to Fix a Running Toilet

June 17, 2026

What You’ll Need

Steps

  1. Shut off the water supply. Find the shut-off valve behind the toilet, near the floor. Turn it clockwise until it stops. Flush the toilet to drain the tank.
  2. Remove the tank lid. Lift the lid straight up and set it on a flat, stable surface. Ceramic cracks easily, so handle it with care.
  3. Check the flapper valve. Find the rubber flapper at the bottom of the tank. Press down on it with your finger. If the running sound stops, the flapper is the culprit. I’ve fixed three toilets in my house, and nine times out of ten, a worn flapper is the problem. Replace it if it looks warped, cracked, or feels spongy.
  4. Adjust the float. Bend the float arm down slightly, or turn the adjustment screw on newer models. Set the water level about 1/2 inch below the top of the overflow tube. This stops water from spilling over.
  5. Clean the fill valve. Unscrew the cap counterclockwise, pull it off, and soak it in white vinegar for 15 minutes. Scrub away residue with a toothbrush, then snap it back in place. Hand-tighten only.
  6. Turn the water back on and test. Place the lid back on the tank. Open the shut-off valve counterclockwise. Wait for the tank to refill fully, then flush. The running sound should be gone.

Pro Tips

Tip: Take a photo of the inside of your tank before taking anything apart. It saves you from guessing how things line up later.

Caution: Never overtighten plastic nuts or valves inside the tank. Hand-tighten plus a quarter turn with a wrench at most. Plastic parts crack easily. A cracked fill valve will leak water into the tank cavity and can damage your floor.

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