The short answer
If your basement floods after heavy rain, stay out of the water until you're sure it isn't touching electrical outlets or the panel, then find where it's coming in, photograph the damage, and start removing water and drying within 24 to 48 hours. Rainwater that comes through walls or floor drains can carry contaminants, so wear boots and gloves, and call a professional for anything more than a small amount.
Step 1: Make it safe
Water and electricity are the biggest immediate danger in a flooded basement. Furnaces, water heaters, washers, dryers and outlets all sit at floor level. If water may be touching any of them, don't wade in. If you can reach the breaker panel from a dry spot, switch off power to the basement. If the panel itself is in the water, leave it alone and call an electrician or your utility.
Step 2: Figure out where the water is coming from
| Where you see water | Likely cause |
|---|---|
| Around the sump pit | Sump pump failed, lost power or couldn't keep up |
| Coming up the floor drain, with a sewage smell | Sewer backup |
| Along the floor-wall joint or through wall cracks | Groundwater pressure after saturated soil |
| Under or around basement windows | Window wells filling with rain |
| Near where downspouts drain | Gutters overflowing or downspouts dumping water at the foundation |
If it's the sump, see sump pump failure water damage. If it's sewage, stop using water in the house and see sewage backup cleanup.
Step 3: Document everything
Before you move anything, photograph and video the water level, where it's coming in, and every damaged item. Insurers usually want to see the damage as it was. Then check your policy: rain seepage, sump failures and sewer backups are often treated differently from a burst pipe. See does insurance cover water damage.
Step 4: Remove water and wet belongings
- Use a wet-dry vac or pump for small amounts; call for professional water extraction if water is deep or covers the floor.
- Get rugs, cardboard boxes and upholstered items out of the water. Cardboard and paper absorb water fast.
- Pull wet carpet back if you can, since the pad underneath holds a lot of water.
Step 5: Dry it within 24 to 48 hours
The EPA advises drying water-damaged areas within 24 to 48 hours to prevent mold. Run fans and a dehumidifier, and keep basement windows closed if it's humid outside. Finished basements are harder: water wicks up drywall and into wall cavities where fans can't reach. That's where professional structural drying with moisture readings makes the difference.
Step 6: Prevent the next one
- Clean gutters and extend downspouts several feet away from the foundation
- Add covers to window wells
- Test the sump pump each season and consider a battery backup
- Ask a plumber about a backwater valve if water came up the floor drain
- Have foundation cracks evaluated and sealed
The St. Louis area can get extreme rain fast: on July 26, 2022, about 9 inches fell at Lambert Airport by noon. If your basement has already flooded, we can connect you with a provider for flooded basement help in Chesterfield and nearby towns. More detail is on our flooded basement cleanup page.