Right now

A main line backup. This is sewage. Stop using water and stay out of it.

The IICRC S500 classes waste line backflow from beyond a trap as Category 3, grossly contaminated water that can carry pathogens. Every flush and every load of laundry adds to it.

Stop running any water in the house. No flushing, no showers, no dishwasher, no washing machine. Keep children and pets out of the room. If water is near outlets or a furnace, turn off that breaker.

What is probably happening

Sewage rises at the lowest fixture, usually a basement floor drain, a tub or a shower, because the main line to the street is blocked.
Causes are tree roots, a collapsed section, grease, or a municipal main surcharging during heavy rain.
If it only happens when it rains hard, the city main may be the source. Call the utility as well as a plumber.

Do this in the next five minutes

Stop all water use in the house. Tell everyone at home.
If there is an outdoor cleanout (a capped pipe near the foundation), a plumber may ask you to open it to relieve pressure. Ask before you do it. Sewage will come out.
Call your water and sewer utility. If the blockage is in their main, they clear it and you do not pay.
Do not touch the water without waterproof boots, gloves and eye protection. Ohio Department of Health guidance is an N95 mask as well.
Photograph everything for insurance before anything is moved or cleaned.

Do not

Do not run water to 'flush it through'. It comes back up.
Do not pour drain cleaner into a main line. It sits there and burns the plumber who opens it.
Do not keep porous items that got wet. Ohio Department of Health: cardboard, mattresses, upholstered furniture and drywall that touched sewage should be discarded.
Do not clean it up yourself if it is more than a few square feet. This is a biohazard job.

Who to call

A licensed plumber with a main line auger and a camera

A plumber clears the line and puts a camera down it to find the cause. Restoration and biohazard companies clean, they do not clear.

Also: Biohazard. Once the line is clear, call a sewage or biohazard cleanup company for anything beyond a small puddle on a tiled floor. Category 3 water needs disinfection and removal of porous materials. Questions for that call ›

Get a free shortlist The seven questions for this trade

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What it should cost

$99 to $1,600, averaging $380

Clearing a main sewer line clog. Snaking $100 to $250, hydro jetting $350 to $600, camera inspection $200 to $1,300. A collapsed line is a separate repair

Source: Angi, main sewer line clog repair cost, updated July 2026. View source

National published range, not a quote for your job. The full cost table for this trade is on the plumbing page.

Ask this contractor, on the phone, before anyone comes out

Tap each one as you ask it.

Will you run a camera after clearing, and can I have the video?
Is this roots, grease or a broken pipe, and how do you know?
Snake or jet, and why that one for my line?
If you find a break, will you locate it on the surface and mark the depth before quoting a repair?
Is the cleanup in this price, or do I need a separate company for that?

End the call if

A quote to dig up or line the sewer before a camera has been run and you have seen the video.
A plumber who says the camera is not needed after a backup.
Anyone who starts demolition or cleanup before the line is clear.

Insurance. Most homeowners policies do not cover sewer backup unless it is added as an endorsement, which the Insurance Information Institute puts at $40 to $160 a year. Check your policy before you assume.

Where this comes from

Not my problem, tap through instead Every plumbing answer