Basement Flooding in St. Louis, MO: Causes & Fixes

Why is water coming into my basement?Basement flooding in St. Louis usually comes from combined sewer backups in older areas, groundwater during heavy rain, or plumbing failures in the basement. Brick homes with century-old foundations and floor drains connected to the sewer are especially vulnerable. Multi-family flats share mains, so a backup can reach every unit with a basement fixture. Knowing whether water rises from the floor drain or seeps through the walls is the quickest way to tell a sewer problem from a groundwater problem, and the fixes are completely different.

Act now

Standing water near electrical equipment is dangerous, and every hour of flooding increases damage. Act immediately.

Call (866) 417-0220

Why it happens in St. Louis

Combined sewer surcharge

Storms fill combined sewers and push water up floor drains.

Old foundations

Century-old foundations let groundwater seep in during heavy rain.

Shared mains

Flats share laterals, so clogs back up into basements.

Sump pump failures

Pumps fail during storms from age or outages.

Downspouts tied into drains

Some older homes have downspouts connected to underground drains or the sewer, adding storm water that overwhelms the system in heavy rain.

Signs to watch for

Water around the sump pit or floor edges
Water coming up through the floor drain
Water near the water heater or washer
Damp walls after rain
Musty smell and efflorescence on walls

Emergency, or can it wait?

Call right away if…

Water near outlets, the panel or appliances
Sewage in the basement
Water rising during a storm

Usually OK to schedule if…

Minor dampness after rain with no standing water

What St. Louis homeowners can check first

Is water coming from the floor drain or walls?
Did it start during heavy rain?
Is the sump pump working?
Is there a backwater valve?
Do downspouts connect to underground pipes?

Unfinished basement with exposed pipes — Stock photo: Oleksandr Chernobai / Unsplash

How our plumbers fix it

Test the sump pump, float and check valve.
Inspect the floor drain and main line.
Check supply lines, water heater and washer hoses.
Evaluate downspouts and grading.

Basement Flooding in St. Louis: questions

How do I protect a St. Louis basement from sewer backups?

A backwater valve blocks reverse flow; pair it with a sump pump and backup for groundwater.

Does MSD help with basement backups?

MSD has offered programs for certain backup situations; check current options.

Is basement floodwater dangerous?

Sewer water is contaminated; avoid contact and discard soaked porous materials.

Will insurance cover basement flooding?

Sewer backup and flood typically need separate coverage.

Should I disconnect my downspouts in St. Louis?

Where downspouts tie into the sewer, disconnecting them and directing water away from the foundation can reduce backups; check local rules first.

Next steps

Sump Pump RepairSump pump repair restores a basement or crawl space pump that collects groundwater in a pit and pumps it away from the foundation.Sump Pump InstallationSump pump installation involves a sealed or lidded basin set into the floor, a properly sized pump, a check valve, discharge piping routed away from the foundation, and a dedicated outlet.Main Sewer Line CleaningThe main sewer line carries all of a home's wastewater to the city sewer or septic tank.Emergency PlumbingEmergency plumbing is urgent repair work for a problem that is actively causing water damage, a sanitation hazard, a gas risk or a total loss of water or drainage in a home.

National guide: Basement Flooding · Plumbing in St. Louis · Basement Flooding in Kansas City · Basement Flooding in Chicago · Basement Flooding in Indianapolis