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How to stop a toilet overflow

You have a few seconds and two easy moves to stop the water. Here's what to do, how to clear the clog, and how to clean up safely.

Updated · 5 min read

You flush, and instead of draining the water keeps rising. It's one of the most common household panics, and the good news is you can usually stop it in seconds without tools. The trick is to stop new water from coming in, then deal with the clog.

The bowl only overflows because the tank keeps sending water into a bowl that can't drain. Cut that off and the problem stops getting worse.

Stop the water first

  1. Take off the tank lid. Lift it straight up and lay it across the closed seat or on a towel on the floor. Tank lids are heavy porcelain and break if they fall.
  2. Push the flapper down. Reach into the tank (the water there is clean) and press the round rubber flapper at the bottom center onto its seat. This stops tank water from flowing into the bowl.
  3. Lift the float. With your other hand, raise the float, the ball or cup that rides on the water, to stop the tank from refilling.
  4. Turn off the supply valve. Find the small valve on the wall or floor behind the toilet, where the supply line connects. Turn it clockwise until it stops. If you can't reach while holding the float, let go and close the valve quickly.
  5. Watch the bowl. Give it a minute or two. Often the water slowly drains down on its own.

Clear the clog

Once the water has stopped rising, it's time to plunge. Don't flush again to test it. That's how a near miss becomes a flood.

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  1. Get a good seal. Fit the plunger's flange into the drain opening at the bottom of the bowl. There should be enough water in the bowl to cover the cup.
  2. Plunge with steady strokes. Push down gently for the first stroke to push out air, then pump firmly up and down several times, keeping the seal.
  3. Check the drain. When the water rushes out, the clog is moving. Repeat if it drains slowly.
  4. Test carefully. Open the supply valve, let the tank refill and flush once while keeping your hand near the flapper, ready to push it down.

If plunging fails, a toilet auger can reach clogs a plunger can't. Skip chemical drain cleaners in a toilet. If they don't work, you're left plunging a bowl full of harsh chemicals. Our guide to unclogging drains without chemicals covers more options.

Clean up safely

Overflow water from a toilet bowl can carry germs, so clean it up like any sewage spill.

  • Wear rubber gloves and keep children out of the area until it's cleaned.
  • Soak up the water with old towels, open a window or run a fan, and dry the floor completely.
  • Disinfect hard surfaces. State health departments suggest about a quarter cup of household bleach in a gallon of water. Use a household disinfectant on surfaces bleach would damage, following its label.
  • Never mix bleach with ammonia or other cleaners. It makes a toxic gas.
  • Throw away rugs, bath mats and other items that can't be washed thoroughly. Launder the rest.
  • Wash your hands well when you're done.

If water got under the flooring, into a ceiling below, or behind a vanity, it needs to dry fully to avoid mold. Renters should tell the landlord about any water damage right away.

When to call a pro

Call a plumber if a plunger and auger won't clear it, if more than one drain is backing up at once, if water comes up in a tub or floor drain when you flush, or if the toilet clogs again and again. Those point to a blockage farther down the line, which needs a plumber's equipment.

Keep it from happening again

  • Flush only toilet paper. Wipes (even ones labeled flushable), paper towels and hygiene products can clog the line.
  • Keep a plunger next to every toilet so nobody has to search for one.
  • Make sure everyone in the house knows where the supply valve is.
  • If the toilet keeps running after flushes, fix it. See how to fix a running toilet.

Common questions

What's the fastest way to stop a toilet from overflowing?

Lift the tank lid and push the rubber flapper at the bottom of the tank down onto its seat. That stops more water from entering the bowl. Then turn off the supply valve behind the toilet.

Should I flush again to clear the clog?

No. Each flush sends a full tank into a bowl that can't drain. Plunge first and only flush once the water level has dropped back to normal.

What can I use to disinfect after a toilet overflow?

Health departments suggest a mix of about a quarter cup of household bleach per gallon of water for hard surfaces, used with gloves and good ventilation. Never mix bleach with ammonia or other cleaners.

What if the supply valve won't turn?

Don't force it, because an old valve can break. Keep holding the float up to stop the refill, and if you need to, close your home's main water shutoff.

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