What Causes Water to Come Up Through a Floor Drain?

Why the Basement Drain Overflows First

In most homes, the basement floor drain sits lower than any other opening on the sewer system. When the pipe between the house and the street slows down or stops, water from every sink, toilet, shower and appliance upstairs looks for the lowest way out. That is the floor drain.

Older Minnesota homes are especially likely to have a floor drain tied directly into the sanitary sewer, and some older houses still carry clay or cast iron sewer pipe that cracks, shifts or lets roots in over time.

Flooded Basement Services That Fit This Question

• Floor Drain Backup Cleanup

  Contaminated water cleanup when a floor drain in the basement, laundry room or garage backs up.

• Sewage Backup Cleanup

  Contaminated water removal and disinfection after a main sewer clog or a city sewer surge floods the basement.

• Sump Pump Failure Cleanup

  Cleanup after an outage, a stuck float or a worn pump lets the sump pit overflow across the slab.

Common Causes of a Floor Drain Backup

A clog in the house sewer pipe is the most common cause. Grease, wipes, hair and debris build up until water backs up. Tree roots find cracks in older clay pipe and grow into a mat that catches everything else.

Heavy rain and spring snowmelt cause the other big category. Water that leaks into sanitary sewers through cracked pipes, or from sump pumps and downspouts piped into the sewer, can push the city sewer past capacity. When that happens, sewage can rise back up house pipes and out of the lowest drain. Many Minnesota cities ban sump discharge into the sanitary sewer for exactly this reason.

Sometimes the cause is inside the house: a washing machine draining into a slow pipe, a discharging relief valve on the water heater or a failed backflow valve.

• Grease, wipes and debris in the house sewer pipe
• Tree roots in older clay or cracked pipe
• City sewer overload during heavy rain or snowmelt
• A collapsed, sagging or offset section of pipe
• Large washer or appliance discharge into a slow drain
• A missing or stuck backwater valve

Why the Water Is Treated as Category 3

Basement drain water usually traveled through the sanitary sewer, even if it looks fairly clear. Restoration crews treat sewage backup as Category 3 the moment it happens, because it can carry bacteria, viruses and debris.

That changes the plan. The cleanup crew suits up in protective gear, builds containment, adds HEPA air scrubbers if the job calls for them, and discards porous materials the backup reached, including drywall, insulation, carpet and pad. Hard surfaces such as the slab and framing get cleaned with an EPA-registered antimicrobial, then drying techs dry the structure with LGR dehumidifiers and air movers until every reading hits the dry target.

Mold can start growing within 24 to 48 hours on wet materials, so the cleanup should not wait.

• No flushing, showers, laundry or sink use upstairs
• Children and pets stay upstairs
• Do not touch the water or wet items without gloves and boots
• Take photos of the backed-up drain and how high it rose

Get the Backup Cleaned Up and Prevent the Next One

A plumber clears the clog, scopes the sewer pipe with a camera and can talk about a backwater valve or pipe repair. The restoration crew takes on the water, the contaminated materials and the drying, and records documentation for the insurance claim. Sewer backup is often covered only through a water backup endorsement, and coverage depends on your policy, so check with your own insurer.

Minnesota Flooded Basement Pros keeps 24/7 dispatch running for floor drain and sewer backups. Call (888) 432-4933 and get the Category 3 cleanup started.

More Flooded Basement Questions

• Does Insurance Cover a Flooded Basement in Minnesota?
• How to Dry a Finished Basement After Water
• What to Do When the Sump Pump Fails
• Why Do Minnesota Basements Flood in Spring?