Short answer: Do not walk into a flooded basement until you know the power is off. The EPA advises making sure the electricity is off and watching for structural hazards before going in, wearing boots, gloves, goggles and an N95 respirator, and drying everything within about 24 to 48 hours to limit mold. Find out where the water came from (rain, a burst pipe, the sump pump or a sewer backup), because sewage water needs professional cleanup.
Quick diagnosis
| What you notice | Most likely cause | What to check | Call a pro? |
|---|---|---|---|
| Water after heavy rain or snowmelt | Groundwater or surface runoff | Check sump pump, gutters, grading | Often |
| Water spreading from one spot, any weather | Burst pipe or water heater | Shut off the main water valve | Plumber |
| Water coming up from the floor drain, smells of sewage | Sewer backup | Stop using water upstairs | Yes, plumber and restoration |
| Pit full, pump silent | Failed sump pump or power outage | Check power and the float | Yes |
| Water over outlets, appliances or the furnace | Electrical and equipment hazard | Stay out; call electrician or utility | Yes |
First: make it safe
- Stay out if water may be touching outlets, cords, the panel or appliances. Have the utility or an electrician cut power if you cannot reach the breaker from a dry spot.
- If you smell gas, leave the house and call the gas company.
- Never run a gasoline pump or generator inside. The EPA says generators must be outside and at least 20 feet from the building.
- Wear rubber boots, gloves, goggles and an N95 respirator. Children, older adults and people with asthma should stay away from the cleanup.
Stop the water
- Burst pipe or water heater: shut off the main water valve (and the water heater power or gas).
- Sewer backup: stop using sinks, toilets, showers and the washer until a plumber clears the line.
- Sump pump: restore power, free the float, or rent or buy a pump.
Clean up within 24 to 48 hours
- Remove the water with a pump or wet-dry vacuum (once power is safe).
- Bag and remove items that cannot be cleaned and dried: wet carpet and pad, cardboard, mattresses, upholstered furniture, soaked drywall and insulation.
- Clean hard surfaces with water and detergent and dry them. Do not mix cleaning products.
- Run fans and dehumidifiers with windows open, but do not use fans if mold is already growing; clean it first.
- Do not run the furnace or AC until the system and ducts are checked.
When to call a professional
- The water is from a sewer backup, toilets or outside floodwater (contaminated).
- More than a small area is wet, or water got into walls and under flooring.
- Water reached the furnace, water heater, electrical panel or outlets.
- You cannot dry it out within about two days, or mold appears.
What it usually costs
HomeGuide (2026) reports basement flood cleanup and repair at about $2,000 to $8,000 for a small to medium basement (most around $5,000). Water extraction, drying and sanitizing runs about $4 to $12 per square foot; mold remediation adds $15 to $30 per square foot.
Frequently asked questions
How fast does mold grow after a basement flood?
Mold can start within 24 to 48 hours, which is why fast drying matters.
Is a flooded basement covered by insurance?
It depends on the cause. Standard policies often exclude outside flooding and sewer backups unless you have flood insurance or a sewer backup endorsement. Burst pipes are more often covered.
Can I use a shop vac on a flooded basement?
Yes, once the power to the area is safe. For more than a few inches of water, a submersible pump is faster.
Related problems
- Water in basement after rain
- Sump pump not working
- Basement floor drain backing up
- Musty smell in basement
- Water heater leaking
Sources
- U.S. EPA: The flooded home (cleanup and indoor air)
- HomeGuide: Basement flooding repair cost (2026)
- This Old House: What to do when your sewer backs up
This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.