Flooded Basement in Milwaukee? What to Do in the First Hour

Is It Safe to Go Down There?

Not until the power to the basement is off. Water plus live outlets, a furnace, a water heater or an extension cord is how people get hurt, so electricity comes before your belongings.

Electricity. If your breaker panel is upstairs, or you can reach it from a dry spot, switch off the main breaker or the basement circuits. If the panel is in the basement and you would have to step into water to reach it, do not go down. Call an electrician. MMSD's own storm advice is blunt: do not go into a basement with standing water, and either wait for it to drain or have a qualified electrician disconnect the power first. Never flip a switch or unplug anything while you are standing in water.

Gas. If you smell gas, do not turn lights on or off and do not use anything that can spark. Get everyone out of the house and call from outside.

Sewage. If the water came up through the floor drain, or it is gray, dark or smells like sewer, treat it as sewage. The CDC's guidance is rubber boots, rubber gloves and goggles, and keeping children and pets away until cleanup is done. Throw out any food, drinks or medicine that the water touched. Also, never run a gas-powered generator or pump inside the house, basement or garage.

Is It Groundwater, a Sewer Backup or a Burst Pipe?

Look at where the water is coming in and what it looks like. Clear water at the walls or the sump pit is usually groundwater. Dirty, smelly water coming up the floor drain is a sewer backup. Water pouring from above, or a hissing sound, is a pipe.

Groundwater. Clear water seeping in where the wall meets the floor, through cracks, through old mortar joints, or overflowing a sump pit whose pump has died or lost power. It shows up during heavy rain and spring snowmelt, when the clay around Milwaukee foundations is saturated and the water table rises. MMSD names naturally high groundwater in wet weather and snowmelt as a common cause of seepage.

Sewer backup. Gray or black water rising out of the floor drain, the basement toilet or the laundry tub, usually with a sewer smell. MMSD's test is simple. If your neighbors are backing up at the same time during a storm, the public sewer is probably full and pushing water back up your lateral, the pipe that runs from your house to the main in the street. If only your house backs up, especially in dry weather, your own lateral is probably blocked by roots, grease, wipes or a collapsed section. Parts of the City of Milwaukee and Shorewood are on combined sewers that carry stormwater and sewage in the same pipe, but backups happen across the region. After the August 9-10, 2025 storm, MMSD received more than 1,100 reports of water backing up into basements.

Burst or leaking pipe. Water spraying or dripping from the ceiling, a supply line, the water heater or a washing machine hose. It is clean at first, and it keeps coming until you shut the main valve. In Milwaukee, frozen pipes along outside walls are a winter classic.

Who Do I Report a Sewer Backup to in Milwaukee?

Your own municipality first, then MMSD if they can't help. In the City of Milwaukee, call the city call center at (414) 286-CITY (2489) or use the city's online request for "backwater in basement."

The Milwaukee Metropolitan Sewerage District (MMSD) is the regional agency that treats wastewater for 29 communities. It runs the big regional sewers and the 28-mile Deep Tunnel. The local sewer pipes under your street belong to your city or village. So in Wauwatosa, West Allis, Greenfield, Shorewood, Whitefish Bay or any other suburb, start with your own public works department.

If your municipality can't help, MMSD asks you to call (414) 272-5100. MMSD also has an online "Report a Wet Basement" form on mmsd.com. It asks how high the water got, whether it looked like clear stormwater or gray or black sewage, and where it came in (floor drain, sump, crack, window). A copy goes to your municipality. Reporting won't pump out your basement, but it helps MMSD and your municipality track where flooding happened. For help with damage, MMSD also points people to 211.

One thing to know: the lateral from your house to the main is generally the homeowner's responsibility to maintain. Where your part ends, at the property line or at the main, varies by municipality. If only your house keeps backing up, a plumber with a camera can tell you whether the lateral is the problem. MMSD's Pipe Check Program offers incentives toward replacing a failing lateral.

Will Insurance Cover My Flooded Basement?

Maybe. It depends on where the water came from and what your policy says. The usual pattern: a sudden burst pipe is often covered, groundwater and outside flooding are often excluded, and a sewer backup usually needs a separate endorsement.

• Burst pipe or appliance leak: standard homeowners policies generally cover sudden and accidental discharge from plumbing. A claim can be denied if the insurer decides the damage came from neglect, like a pipe left to freeze in an unheated space, or a slow leak that went on for months.
• Groundwater seeping through the foundation: usually excluded. The standard policy form specifically excludes water below the ground surface that seeps or leaks through a foundation.
• Sewer or drain backup and sump pump overflow: excluded from a typical policy unless you added water backup coverage as an endorsement. Flood insurance doesn't cover it either.
• Outside flooding: excluded from homeowners policies. Flood insurance through the National Flood Insurance Program covers only limited items in a basement, like the furnace, water heater and sump pump, and not finished walls, carpet or furniture.

Policies differ, so read your own declarations page and call your agent. Don't throw out damaged items until the adjuster has seen them or told you photos are enough, and keep every receipt.

What Does Flooded Basement Cleanup Involve?

Four stages: pump or extract the water, tear out what can't be saved, clean and disinfect, then dry with fans and dehumidifiers until moisture readings are back to normal. Get a written estimate before any of it starts.

A water cleanup company typically brings pumps and extraction vacuums for the standing water, pulls wet carpet and pad, cuts out soaked drywall and insulation above the water line, and cleans and disinfects what stays, which matters most after a sewer backup. Then come air movers and dehumidifiers, left running until moisture readings show the walls, floor and framing are actually dry. For how that drying works, the clean, gray and black water categories, and how to choose a company, see our guide to water damage restoration in Milwaukee.

Why the written estimate first: a stressed homeowner will sign anything on a flooded day. Ask for the scope and price on paper before work starts: what gets removed, how many days of equipment, how they will document moisture readings for your insurer, and what you owe if insurance pays less than expected. Read carefully anything that asks you to sign over your insurance payment directly to the contractor.

Cleanup only fixes this flood. It does not stop the next one.

After the Cleanup, How Do I Stop the Next One?

Fix the path the water took. A dead sump pump, a sewer lateral that backs up, and groundwater pushing through the walls each have a different fix.

If the sump pump failed: it usually quits in exactly the storm that knocks out the power. A correctly sized pump plus a battery backup is the most common fix. See sump pump installation and our guide to a sump pump battery backup in Milwaukee.

If groundwater came through the walls or floor: start with the cheap outside fixes in wet basement after heavy rain (downspouts, grading, gutters). If water still gets in, the long-term answers are interior basement waterproofing with drain tile, or exterior waterproofing. Hydrostatic pressure on basement walls explains why saturated clay pushes water in.

If it was a sewer backup: have a plumber camera the lateral, ask whether a backwater valve fits your plumbing, look at MMSD's Pipe Check Program, and add sewer backup coverage to your insurance.

For the bigger picture, see our overview of basement waterproofing in Milwaukee. Call (414) 240-1817 and press 2, and we connect you with a local waterproofing company. Ask them to explain the water path and put the quote in writing.