Symptoms
- Water rising above the pit rim onto the basement floor
- Pump running but clearly not keeping pace with incoming water
- Happens during very heavy rain or a power outage
Likely causes
- CommonPump undersized or failing under heavy inflowVery heavy storms can bring more water than a marginal or aging pump can handle.
- CommonPower outage stopping the pump during a stormStorms that knock out power are often the same storms that generate the most water, a bad combination without a backup.
- PossibleDischarge line clogged, frozen, or too smallEven a working pump can't keep up if the water has nowhere to go once pumped out.
What to do
- If overflow is happening now and power is out, use a battery backup pump if you have one, or a wet/dry vacuum to manually reduce the water level.
- Check the discharge line outside for a clog, ice blockage, or a valve that's shut, which would explain a working pump not actually moving water away.
- Once the immediate situation is under control, clean debris from the pit and check that the pump and float move freely.
- Consider a battery backup or water-powered backup sump pump for protection during power outages.
- Evaluate whether the current pump's capacity matches your situation, especially if this happens in normal heavy rain, not just extreme storms.
- Have a plumber assess pump sizing, add a backup system, or install a second pump for high-risk basements.
- After the water is cleared, dry the area thoroughly and watch for mold in the following days.
Tools and parts
- Wet/dry vacuum
- Bucket
Battery backup sump pumpSearch: “sump pump battery backup system”
When to call a pro
Call a plumber to upsize the pump or install a battery or water-powered backup system for future storms.
Safety
Use caution
Turn off power to any submerged outlets or equipment at the breaker, and avoid contact with electrical items near standing water.