What do I do when a toilet is overflowing?

Work through these in order. Stop as soon as the water stops rising.

1. 1Stop flushing. Every extra flush sends more water toward the bowl rim.
2. 2Shut off the toilet's supply valve. It's the small valve on the wall or floor behind or beside the toilet. Turn it clockwise. Korky's overflow guide gives the same first step: "turn off the water supply immediately," then turn the valve "clockwise until the water stops."
3. 3If the valve is stuck or out of reach, lift the float. Remove the tank lid, and lift the float ball or cup high enough to stop the water from running. That closes the fill valve so no new water enters the tank.
4. 4Put towels around the base. Get them down before the water reaches the floor drain or a wall.
5. 5Bail some water out of the bowl. Oatey says to remove excess water so it won't spill when you put the plunger in. A cup and a bucket do the job.

Don't flush again "to see if it clears." If the clog is still there, that flush lands on the floor.

There are three usual causes, and they point to different fixes.

A clog in the toilet or its drain. Korky says water rising in the bowl "usually means the toilet is clogged." The flush water has nowhere to go, so the bowl fills and it comes over the rim. This is the usual reason a bowl overflows when you flush.

A tank that won't stop filling. This is different. It happens with no flush at all. The fill valve fails to shut off, or the float sits too high, and water runs down the overflow tube, the open pipe in the middle of the tank. Fluidmaster calls that pipe "the most important safety feature in a toilet." It's a backup path so a stuck fill valve sends water down into the bowl and away instead of over the tank edge.

A blockage farther down the line. If the toilet overflows and other drains are slow, the blockage isn't in the toilet at all. That's the case that needs a plumber.

Once the water is off and the mess is contained, deal with the clog.

Plunge first. Use a flanged toilet plunger, the kind designed to seal inside the bowl, and make a tight seal around the outlet. Korky says the seal matters because the plunger has to push and pull the clog "without losing pressure," and that "the real power lies in the pulling motion." So pull sharply, and don't just push.

Then use a toilet auger. If plunging doesn't work, Oatey says to try a toilet auger, which reaches deeper blockages. It's not the same as a drain snake, which has no guard for the porcelain. See the difference between a toilet auger and a drain snake before you buy or borrow one. If you have neither tool handy, how to unclog a toilet without a plunger has other options.

When the bowl drains normally, turn the supply valve back on slowly, and let the tank refill before you flush.

Then the water isn't coming from the tank. Shut off the whole house's water at the main valve if you can't stop the flow any other way. If water keeps coming up after that, the problem is a sewer backup and you need a plumber right away. Korky says the same about serious clogs: "There can even be blockages further down the sewer line."

That matches what you'd expect. When a main sewer line is blocked, wastewater from everything in the house has nowhere to go, and it comes back up through the lowest drain. That is often the shower, tub or a floor drain, and sometimes the toilet.

Other signs of a sewer line problem:

• A tub or shower fills when you flush the toilet or run the washer.
• Several fixtures gurgle or drain slowly at once.
• Sewage shows up in a sink, tub or floor drain.

Our guides on water backing up in the shower when you flush and main line vs branch clogs go through these signs in more detail. For a Phoenix angle, see why drains back up during monsoon.

Stop using water in the house until the line is cleared. Every flush, shower or load of laundry adds to what's already backed up. At HQ Plumbing and Air, we offer 24/7 emergency service, and we give you the price up front before any work starts.

Treat the water as contaminated. Toilet overflow water can carry human waste. The CDC's guidance for sewage-contaminated cleanup says to wear rubber boots, rubber gloves and goggles when sewage is involved.

Then:

1. 1Get the standing water out. Mop or wet-vacuum the floor and keep kids and pets out of the room.
2. 2Wash hard surfaces with soap and water, then disinfect. The CDC gives a mix of 1 cup of household bleach per 5 gallons of water for non-food household surfaces. It also says: "Never mix bleach with ammonia or any other cleaner." Open windows and doors for fresh air while you work.
3. 3Dry the area fast. The CDC says to clean up and dry your home within 24 to 48 hours if possible, since delay increases mold growth. Run fans and open windows.
4. 4Throw out what can't be cleaned. The CDC says to discard porous items that sewage has soaked, like carpet, mattresses and upholstered furniture, and to remove and discard drywall and insulation contaminated with sewage.

A single bowl of clean-ish overflow from a clogged toilet is a small cleanup. A backup of sewage from a main line is a larger one, and you may want a restoration company to handle drywall and flooring.

### How do you keep it from happening again?

Most overflows trace back to habits. Keep wipes, paper towels and feminine products out of the toilet, since they are common clog makers. See whether flushable wipes are really safe to flush. If a toilet clogs again within days, look at why your toilet keeps clogging.

If the overflow came from the tank, check the float and fill valve. A fill valve that won't shut off is a simple fix, and how to fix a running toilet shows the steps. And keep in mind that Fluidmaster warns bleach and chlorine tank cleaners damage toilet parts, so skip those tablets.

Know where the shutoff valve is before you need it. Turn it once a year to make sure it moves. A valve that's stuck when the bowl is filling is the worst time to find out.