Why Your Basement Floor Drain Backs Up After Heavy Rain in St. Louis

A frustrating — and very local — problem

It rains hard for an hour, and suddenly water is rising out of the floor drain in the middle of your basement. Sometimes it's clear storm water. Sometimes it's gray or smells like sewage. Either way, it's one of the most common calls we get after a big St. Louis storm, and it almost always has a fixable cause.

The key is figuring out where the water is coming from, because a floor drain is connected to several systems at once, and the fix depends on which one is overloaded.

How your floor drain is connected

In most St. Louis area homes, the basement floor drain connects to the home's sewer lateral, which carries wastewater to the public sewer. Because it's the lowest drain in the house, it's the first place water appears when anything downstream can't keep up. In some older homes, downspouts, foundation drain tile or areaway drains were also tied into the same line — which sends large volumes of rain water into a pipe meant for household wastewater.

The most common causes

How to tell which one you have

• Backs up during rain AND when the washer drains: likely a restricted lateral.
• Only backs up during heavy rain, and the water is mostly clear: possible downspout or drain tile connection, or surcharging public sewer.
• Neighbors on the street have backups during the same storm: points toward the public sewer.
• Water seeps in at the walls or floor cracks: groundwater and drainage, not the sewer.
• A camera inspection of the lateral is the fastest way to confirm what's going on.

Fixes that actually work

What to do during a backup

Stop using water in the house, keep people and pets away from sewage, and don't try to plug the floor drain with a heavy object — the pressure will find another outlet, like a toilet or shower. Once the storm passes, have the line cleared and inspected, and clean affected areas with proper sanitizing.

Get your basement protected before the next storm

City & County Plumbing and Drain diagnoses floor drain backups across St. Louis City, St. Louis County and St. Charles County. We'll find the cause and recommend the fix that fits — not just clear the drain until the next storm. Call (636) 243-8881.