Short answer
Anderson basements leak most in late winter and spring because snowmelt and early rain soak into ground that drains slowly, and the seasonal water table rises toward the surface. Anderson averages about 20.8 inches of snow a year (NOAA normals). Prepare before the thaw: clear snow from the foundation, make sure downspouts and the sump discharge are open, and test the pump and backup.
Do this first If water is coming in now during a thaw, check that the sump pump runs and that its discharge outlet outside isn’t frozen or buried. Clear snow away from the walls and window wells, and extend any downspout that empties at the foundation.
Why late winter and spring are the worst
Three things line up in an Anderson spring:
- Snowmelt. Anderson averages about 20.8 inches of snow a year (NOAA 1991-2020 normals, Anderson 1 N station). When a snowpack melts, much of it soaks in along the foundation.
- A rising water table. On the city’s slow-draining till, water builds up near the surface in late winter and spring. The soil survey estimates a seasonal water table within about a foot of the surface under 56% of sampled city land (USDA NRCS).
- Frozen outlets. Discharge lines and downspout outlets that froze in winter can still be blocked when the thaw arrives, so water that should leave the property doesn’t.
That’s why a basement that stays dry through summer thunderstorms can leak for weeks in March and April.
What you’ll usually see
- Seepage at the floor-wall joint along several walls
- Water rising through floor cracks
- A sump pump that runs for weeks
- Window wells full of meltwater
Get ahead of it (late fall and winter)
| When | Do this |
|---|---|
| Late fall | Clean gutters after leaf fall; check that downspouts extend 6-10 feet; cover window wells |
| Winter | Keep snow off the foundation, window wells and the sump outlet; check the outlet after each freeze |
| Before the thaw | Test the sump pump and the backup; replace a backup battery that’s near the end of its life |
| During the thaw | Check the pit and the floor edge daily; photograph and date any water |
See discharge and freezing for keeping lines open in winter.
Causes, most likely first
- Groundwater rising under and around the basement: slow seepage at the floor edge or through cracks that lasts for weeks.
- Meltwater soaking in along the foundation: water near snow piles, under downspouts and in window wells, worst on warm afternoons.
- A frozen or buried sump outlet: the pump runs but the pit keeps rising.
- A pump that can’t keep up: the pit stays high even though the outlet flows.
- A combined sewer backup during a rainy thaw: dirty water at the floor drain. See sewer backup or groundwater?
If it leaks every spring
Surface steps reduce the water, but they don’t lower the water table. If seepage returns every spring after the outside is fixed, the basement needs drainage at the footing: interior drain tile and a sump with a backup. Summer and fall are the best time to schedule the work, before the next thaw.
When to call
Call a contractor if seepage comes back every spring, if the pump can’t keep the pit down, or if a wall cracks or bulges during the thaw. Interior drain tile typically runs $40-$120 per linear foot, with a new pit and pump $800-$2,500 (published ranges; sources). A wall that cracks in spring is covered on bowing walls.