After a heavy storm, water in your basement doesn't always mean the same problem. Sometimes it's a sump pump that couldn't keep up. Sometimes it's the city sewer system backing up through your own pipes. They look similar in the first few minutes — but they call for very different responses, and mixing them up can turn a manageable problem into an expensive one.
Here's how to tell them apart, what to do in the first 30 minutes, and what St. Paul homeowners typically pay to get it fixed.
The Fast Way to Tell Them Apart
| Sign | Sump Pump Failure | Sewer Backup |
|---|---|---|
| Where water appears | Pools near the sump pit or foundation walls | Rises through floor drains, a basement toilet, or a shower/tub drain |
| Smell | None, or a faint musty basement smell | Sewage odor — often the first clue |
| Water appearance | Clear or slightly cloudy groundwater | Gray or dark water, sometimes with waste visible |
| What's failing | A pump, float switch, or power issue in your own system | A blockage or overload somewhere in the sewer line — sometimes yours, sometimes the city's |
Quick rule of thumb: if the water smells like sewage or is coming up through a drain rather than pooling near your sump pit, treat it as a sewer backup — not a sump pump issue.
Sewage in the house is a health hazard. Stop using every drain, toilet, and sink in the home until it's addressed — running more water in makes it worse, and contact should be avoided until it's cleared.
What to Do in the First 30 Minutes
If it looks like a sewer backup
- Stop using all drains and toilets immediately — running more water in makes it worse.
- Keep people and pets away from the affected area.
- Don't plunge or snake a backed-up floor drain yourself — under pressure, contaminated water can spray back at you.
- If you have a main sewer cleanout in your yard or basement, don't open it unless a plumber has walked you through it.
- Call a licensed plumber — this is a same-day, not next-week, situation.
If it looks like a sump pump failure
- Check that the pump is plugged in and the breaker hasn't tripped.
- Check the float switch isn't stuck or jammed against the side of the pit.
- If the pump is running but not moving water, or isn't running at all, it likely needs repair or replacement.
- A wet/dry shop vac can manage minor pooling while you wait, but it won't fix the underlying issue.
Why This Happens More After Twin Cities Storms
St. Paul has a mix of older housing stock with aging clay or cast iron sewer lines, and some neighborhoods still run partially combined storm and sanitary sewer systems. During a heavy rain event, two things tend to happen at once: groundwater rises and pushes your sump pump harder than usual, and the municipal sewer system fills up faster than it can drain — which can push backups into homes at the lowest points on a block. Tree roots are a year-round factor too, since mature trees common in older St. Paul neighborhoods send roots toward the moisture inside sewer lines, gradually narrowing or cracking them.
What It Typically Costs to Fix
Costs vary based on cause and severity, but here's a general range homeowners can expect:
- Sump pump replacement — often a same-day fix, generally on the lower end of plumbing repair costs.
- Drain clog or blockage clearing — mid-range, depending on how far into the line the blockage is and whether a camera inspection is needed.
- Sewer line repair (root intrusion, cracked pipe) — higher cost, especially if excavation is required, though trenchless options can sometimes reduce cost and disruption.
- Cleanup and remediation — separate from the plumbing fix itself; this is often where a water damage restoration company gets involved, not your plumber.
- 1Know your main water shutoff location now — before an emergency happens.
- 2Don't use any fixtures if you suspect a sewage backup.
- 3Document the damage with photos before cleanup begins — this can help with an insurance claim.
- 4Call a licensed plumber — a good pro can often triage over the phone whether it needs immediate attention.
Insurance note. Standard homeowners policies typically exclude sewer and drain backups unless you've added a specific rider. Check your policy or call your agent to confirm what's covered before you need it.
One more thing worth ruling out: if this is the second or third time your basement has backed up, the cause may not be the storm at all — recurring backups usually point to tree roots in the sewer lateral.
Tell Pip what's happening
Where the water's coming from, what it smells like, when it started — get a real answer and get matched with a licensed local plumber. Free for homeowners.