Category: Basement & Sump Pump

Short answer: Do not walk into a flooded basement until you know the power is off. The EPA advises making sure the electricity is off and watching for structural hazards before going in, wearing boots, gloves, goggles and an N95 respirator, and drying everything within about 24 to 48 hours to limit mold. Find out where the water came from (rain, a burst pipe, the sump pump or a sewer backup), because sewage water needs professional cleanup.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Water after heavy rain or snowmelt	Groundwater or surface runoff	Check sump pump, gutters, grading	Often
Water spreading from one spot, any weather	Burst pipe or water heater	Shut off the main water valve	Plumber
Water coming up from the floor drain, smells of sewage	Sewer backup	Stop using water upstairs	Yes, plumber and restoration
Pit full, pump silent	Failed sump pump or power outage	Check power and the float	Yes
Water over outlets, appliances or the furnace	Electrical and equipment hazard	Stay out; call electrician or utility	Yes

First: make it safe

1. Stay out if water may be touching outlets, cords, the panel or appliances. Have the utility or an electrician cut power if you cannot reach the breaker from a dry spot.
2. If you smell gas, leave the house and call the gas company.
3. Never run a gasoline pump or generator inside. The EPA says generators must be outside and at least 20 feet from the building.
4. Wear rubber boots, gloves, goggles and an N95 respirator. Children, older adults and people with asthma should stay away from the cleanup.

Stop the water

• Burst pipe or water heater: shut off the main water valve (and the water heater power or gas).
• Sewer backup: stop using sinks, toilets, showers and the washer until a plumber clears the line.
• Sump pump: restore power, free the float, or rent or buy a pump.

Clean up within 24 to 48 hours

1. Remove the water with a pump or wet-dry vacuum (once power is safe).
2. Bag and remove items that cannot be cleaned and dried: wet carpet and pad, cardboard, mattresses, upholstered furniture, soaked drywall and insulation.
3. Clean hard surfaces with water and detergent and dry them. Do not mix cleaning products.
4. Run fans and dehumidifiers with windows open, but do not use fans if mold is already growing; clean it first.
5. Do not run the furnace or AC until the system and ducts are checked.

When to call a professional

• The water is from a sewer backup, toilets or outside floodwater (contaminated).
• More than a small area is wet, or water got into walls and under flooring.
• Water reached the furnace, water heater, electrical panel or outlets.
• You cannot dry it out within about two days, or mold appears.

What it usually costs

HomeGuide (2026) reports basement flood cleanup and repair at about $2,000 to $8,000 for a small to medium basement (most around $5,000). Water extraction, drying and sanitizing runs about $4 to $12 per square foot; mold remediation adds $15 to $30 per square foot.

Frequently asked questions

How fast does mold grow after a basement flood?

Mold can start within 24 to 48 hours, which is why fast drying matters.

Is a flooded basement covered by insurance?

It depends on the cause. Standard policies often exclude outside flooding and sewer backups unless you have flood insurance or a sewer backup endorsement. Burst pipes are more often covered.

Can I use a shop vac on a flooded basement?

Yes, once the power to the area is safe. For more than a few inches of water, a submersible pump is faster.

Related problems

• Water in basement after rain
• Sump pump not working
• Basement floor drain backing up
• Musty smell in basement
• Water heater leaking

Sources

• U.S. EPA: The flooded home (cleanup and indoor air)
• HomeGuide: Basement flooding repair cost (2026)
• This Old House: What to do when your sewer backs up

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.

Short answer: The basement floor drain is the lowest drain in the house, so it is where a main sewer problem shows up first. This Old House lists the usual causes: clogs from wipes and grease, tree roots, sagging or broken pipes, and heavy rain overloading the city sewer. If water rises in the floor drain when you run the washer, flush a toilet or shower upstairs, stop using water and call a plumber to clear the main line.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Water comes up when the washer drains	Partial main line clog	Stop using water; check other drains	Plumber
Several drains slow and gurgling	Main sewer line blockage	Run one fixture and watch the floor drain	Plumber
Backs up only during heavy rain	City sewer overloaded or storm water in the line	Note if neighbors have the same problem	Plumber and city
Clear water, no smell, after rain	Groundwater entering the drain	Check grading and sump pump	Often
Sewage smell but no water	Dry floor drain trap	Pour water into the drain	No

Do this now

1. Stop using all fixtures: toilets, sinks, showers, the washer and the dishwasher.
2. Keep people and pets away from the water; sewage can make you sick.
3. If water is near outlets or appliances, turn off that circuit only if you can reach the panel safely.
4. If you have an outdoor sewer cleanout and can reach it safely, opening the cap can relieve the pressure so sewage spills outside instead of in the basement (This Old House).
5. Call a licensed plumber.

What the plumber will do

• Snake (auger) the main line from the cleanout.
• Hydro jet tough clogs like grease and roots.
• Run a camera to find roots, breaks or a sagging section.
• Recommend a backflow (backwater) device if your area is prone to city sewer surcharges.

Prevent the next backup

• Do not flush wipes (even “flushable”), diapers or paper towels.
• Keep grease, oil and coffee grounds out of drains.
• Have the line inspected if you have big trees near the sewer or an older clay or cast-iron pipe.
• Ask your insurer about a sewer backup endorsement; standard policies often exclude it.

When to call a professional

• Sewage or water comes up through the floor drain.
• More than one drain is slow or gurgling.
• It happens again after the line was cleared (roots or a broken pipe).
• Sewage soaked carpet, drywall or stored items (call a restoration company).

What it usually costs

HomeGuide (2026) lists main line snaking at about $200 to $500, hydro jetting at $600 to $1,400, and a sewer camera inspection at $125 to $500. Sewage cleanup runs about $7 to $15 per square foot, and minor backup repair and cleanup about $500 to $2,000.

Frequently asked questions

Why is my basement floor drain backing up when I do laundry?

The washer sends a lot of water quickly. If the main line is partly blocked, that water backs up at the lowest opening: the floor drain.

Should I pour drain cleaner in a backed-up floor drain?

No. A main line clog is too far away, and the chemicals make the water more dangerous for you and the plumber.

Is sewage in the basement dangerous?

Yes. This Old House notes sewage exposure can cause stomach illness and infections. Wear gloves, boots and eye protection, and leave major cleanup to professionals.

Related problems

• Clogged drain deep in pipe
• Sewer smell in basement
• Flooded basement
• Sewer smell in house

Sources

• This Old House: What to do when your sewer backs up
• HomeGuide: Sewer backup repair cost (2026)

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.

Short answer: Bob Vila lists the main reasons a sump pump stops working: no power (unplugged, dead outlet, tripped breaker), a stuck float switch, a clogged intake screen or impeller, a check valve installed backward or stuck, a blocked discharge line, or a burned-out motor. Test it by pouring a bucket of water into the pit. If it hums but does not pump, or does not start at all after you confirm power, it likely needs repair or replacement.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Nothing happens when the pit fills	No power or failed switch	Test the outlet; check the breaker	If power is fine
Starts when you lift the float by hand	Float switch stuck	Clear whatever jams the float	Rarely
Hums but does not move water	Clogged impeller or intake, or failed motor	Unplug; clean the intake screen	Often
Runs but water comes back	Check valve stuck or installed backward	Check the arrow on the valve	Often
Pump is 7 to 10+ years old	Worn-out motor	Plan a replacement	Yes

Test it

1. Make sure the pump is plugged directly into a working outlet (not a long-term extension cord) and the breaker is on.
2. Slowly pour a bucket of water into the pit.
3. Watch the float rise and the pump start. It should empty the pit and stop.
4. If it does not start, unplug it and lift the float by hand after plugging back in, to see if the float is the problem.

Clean it

Unplug the pump, lift it out if possible, and clear debris from the intake screen and impeller. Check that the discharge pipe outside is not blocked or frozen.

Be ready for the next storm

• HomeGuide suggests testing every three months, and monthly in the rainy season.
• A battery backup pump keeps working during a power outage, when storms often hit.
• Keep a spare float switch or know a plumber who can come quickly.

When to call a professional

• The pump will not start with power confirmed and the float free.
• The motor hums, overheats or trips the breaker.
• The pump is old or water is already rising in the basement.

What it usually costs

HomeGuide (2026) lists sump pump repairs at about $200 to $870 and a replacement pump at about $400 to $700 on average. Battery backup systems add to that cost.

Frequently asked questions

How do I know if my sump pump is bad?

If it does not start when you fill the pit with water, runs but does not lower the water, or makes grinding noises, it may be failing.

How long do sump pumps last?

HomeGuide and Bob Vila put the average at about 7 to 10 years.

Related problems

• Sump pump running constantly
• Water in basement after rain
• Outlet not working
• GFCI outlet won’t reset
• Flooded basement

Sources

• Bob Vila: Why is my sump pump not working?
• HomeGuide: Sump pump repair cost (2026)

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.

Short answer: Water that shows up after heavy rain almost always comes from outside. Clogged gutters, downspouts that dump water next to the house, and soil that slopes toward the foundation let water soak in and push against the walls. The University of Minnesota Extension recommends downspouts that discharge at least 4 feet beyond the wall and soil that slopes away at least 1 inch per foot for the first 6 feet. Fix those first, then seal cracks and consider a drainage system if water still comes in.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Water along one wall below a downspout	Downspout discharging too close	Add an extension (4 ft or more)	No
Water where wall meets floor all around	Hydrostatic pressure from saturated soil	Check grading and gutters	If it continues
Water coming through a crack	Foundation crack	Mark it; seal small cracks	If wider than 1/2 inch
Water below a window	Window well filling with water	Clear the well; add gravel or a cover	Rarely
Water from the floor drain	Sewer or drain backup	See sewer smell in basement	Yes
Damp walls in summer, no rain	Condensation from humid air	Run a dehumidifier	No

Fix the outside first

• Clean gutters in spring and fall, more often with trees nearby.
• Extend downspouts so they discharge at least 4 feet away from the wall.
• Grade soil to slope away from the house at least 1 inch per foot for 6 feet.
• Clear window wells and add gravel or covers.

Then deal with the walls

Bob Vila suggests sealing small cracks with a filler compound and calling a professional for cracks wider than 1/2 inch. If water still comes in after the outside fixes, an interior or exterior drainage system with a sump pump may be needed.

Dry out fast

The EPA says wet materials should be dried within 24 to 48 hours to prevent mold in most cases. Remove wet carpet and boxes, run fans and a dehumidifier, and keep electrical devices away from water.

When to call a professional

• Water keeps coming in after gutters, downspouts and grading are fixed.
• Cracks are wider than 1/2 inch, horizontal or growing (see foundation cracks).
• Water comes up through the floor drain.
• There is mold or a strong musty smell.

What it usually costs

Bob Vila reports professional foundation crack repair at about $250 to $800, exterior French drains at $500 to $10,000, interior drainage systems at $5,000 to $18,000, and interior wall sealing around $3,000 on average.

Frequently asked questions

Why does my basement only leak when it rains hard?

Heavy rain saturates the soil and builds pressure against the walls. Water then finds cracks and the joint between wall and floor.

Will a dehumidifier fix water in the basement?

No. It helps with humidity and odor, but the University of Minnesota Extension notes it is not a complete solution for water coming in.

Related problems

• Sump pump not working
• Sump pump running constantly
• Foundation cracks
• Musty smell in basement
• Sewer smell in basement
• Flooded basement

Sources

• University of Minnesota Extension: Moisture in basements, causes and solutions
• Bob Vila: How to stop water leaking into the basement after heavy rain
• U.S. EPA: A brief guide to mold, moisture and your home

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.

Short answer: A musty odor is a moisture problem. The EPA recommends keeping indoor humidity below 60%, ideally between 30% and 50%, and drying anything wet within 24 to 48 hours. Check humidity with an inexpensive hygrometer, look for damp carpet, boxes, wall coverings and leaks, and fix water coming in from outside. Small areas of mold (under about 10 square feet) can usually be cleaned yourself.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Smell worse in summer	Humid air condensing on cool walls and floors	Measure humidity; run a dehumidifier	No
Smell after rain	Water coming in from outside	See water in basement after rain	If it continues
Smell near carpet or stored boxes	Damp materials growing mold	Lift carpet; check boxes	If large
Visible spots on walls or wood	Mold	Measure the area	If over about 10 sq ft
Smell like sewage, not just musty	Dry floor drain trap or sewer issue	See sewer smell in basement	Often

Measure and lower the humidity

A basic hygrometer costs about $10 to $50 (EPA). Aim for 30% to 50%. Run a dehumidifier, keep it draining, and vent the clothes dryer outside. The University of Minnesota Extension cautions that a dehumidifier helps with humidity and odor but does not fix water coming through the walls.

Find damp materials

• Carpet and pads on concrete floors.
• Cardboard boxes against walls or on the floor.
• Drywall, paneling and insulation against foundation walls.
• Areas under windows, around the water heater, laundry and pipes.

Cleaning small mold areas

The EPA says to fix the water problem first, scrub hard surfaces with detergent and water and dry them completely. Porous materials like carpet and ceiling tiles may need to be thrown away. Do not paint over mold.

When to call a professional

• Mold covers more than about 10 square feet or comes from sewage or flood water.
• Water keeps coming in from outside.
• You suspect mold inside the HVAC system or ducts (EPA advises not running the system).
• Anyone in the house has health concerns related to mold.

What it usually costs

A hygrometer costs about $10 to $50 (EPA). Waterproofing costs depend on the cause: Bob Vila reports professional crack repair at about $250 to $800 and interior drainage systems at $5,000 to $18,000.

Frequently asked questions

What humidity should a basement be?

The EPA recommends keeping indoor humidity below 60%, ideally 30% to 50%.

Is a musty smell always mold?

It means conditions for mold are present. It often comes from damp materials even when you cannot see mold.

Related problems

• Water in basement after rain
• Sewer smell in basement
• Mold on bathroom ceiling
• Sump pump running constantly
• Flooded basement

Sources

• U.S. EPA: A brief guide to mold, moisture and your home
• U.S. EPA: Mold cleanup in your home
• University of Minnesota Extension: Moisture in basements, causes and solutions
• Bob Vila: How to stop water leaking into the basement after heavy rain

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.

Short answer: First look in the pit. If water keeps flowing in, the pump may simply be handling high groundwater or snowmelt, which Bob Vila notes can be normal. If the pit is empty and the pump still runs, the float switch is probably stuck. If the pump runs but the water level does not drop, check for a clogged discharge line, a failed check valve or a worn-out pump. Pumps typically last about 7 to 10 years.

Quick diagnosis

What you notice	Most likely cause	What to check	Call a pro?
Water keeps flowing into the pit	High water table, snowmelt or heavy rain	Watch if it stops when the ground dries	If it never stops
Pump runs with an empty pit	Stuck float switch	Unplug; free the float by hand	If it stays stuck
Pump runs, water level does not drop	Clogged or frozen discharge line, or failed pump	Check the outlet outside	Often
Pump cycles on and off every few seconds	Water flowing back down: bad check valve	Listen for water rushing back after it stops	Often
Pump is old and loud	Worn motor or impeller	Check the age	Yes

Check the pit and the float

1. Unplug the pump before reaching into the pit.
2. Look for objects or debris jamming the float switch and make sure the float can move up and down freely.
3. Plug it back in and pour a bucket of water into the pit. The pump should start, empty the pit and shut off.

Check the discharge line and check valve

Go outside to where the discharge pipe ends. If little or no water comes out while the pump runs, the line may be clogged with dirt or frozen in winter. The check valve (on the pipe above the pump) stops pumped water from falling back into the pit; if it fails, the pump re-pumps the same water over and over.

When the pump is just working hard

After heavy rain or snowmelt, or in homes with a high water table, a pump can run often for days. If it never gets a break, ask a plumber or waterproofing contractor whether the pump is big enough, since an overworked pump burns out early.

When to call a professional

• The pump runs constantly and the water level does not go down.
• The float is stuck and you cannot free it.
• The pump is 7 to 10 years old or older, or makes grinding noises.
• Water is rising toward the top of the pit.

What it usually costs

HomeGuide (2026) puts sump pump repairs at about $200 to $870. Parts are inexpensive (float switch about $20 to $40, check valve about $10 to $30), and a replacement pump typically costs $400 to $700 installed on average. Annual maintenance runs about $100 to $250.

Frequently asked questions

Is it normal for a sump pump to run every few minutes after rain?

Yes, during and after heavy rain or snowmelt it can. It should slow down as the ground dries.

Can a sump pump run dry?

Running dry can overheat and damage the motor, so fix a stuck float quickly.

Related problems

• Sump pump not working
• Water in basement after rain
• Musty smell in basement

Sources

• Bob Vila: Why is my sump pump running without rain?
• Bob Vila: Why is my sump pump not working?
• HomeGuide: Sump pump repair cost (2026)

This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.