Water Coming Up Through the Basement Floor? Causes

Water coming up through basement floor guide graphic

Water on a basement floor is alarming, and the cause is not always obvious. It may seep from cracks, the joint where the floor meets the wall, the floor drain or around the sump pit. The fix depends on where it comes from. This guide helps you sort it out. If the sump pump is the problem, our sump pump repair in McLean service can repair or replace it and add a backup.

This is general information, not engineering or insurance advice.

What should I do first?

Stay safe. Do not walk through water near outlets, cords or the electrical panel. Turn off power to the basement at the breaker only from a dry spot.
Check the sump pump. Is it running? Is water rising in the pit?
Check the floor drain. Is water coming up through it?
Stop using water if the floor drain is backing up.
Move belongings and take photos.

Water coming up through the basement floor: groundwater or plumbing?

Clue	Likely groundwater	Likely plumbing
Timing	During or after heavy rain	Any time, including dry weeks
Where	Cracks, wall-floor joint, around the pit	One spot, a warm area, near pipes
Water meter	Not moving with taps off	Moving with taps off
Water temperature	Cool	Can be warm if a hot line leaks
Floor drain	Not involved	May back up if the sewer is blocked

What causes groundwater to come up through the floor?

After heavy rain, the soil around the house fills with water. That water pushes up against the slab, a force called hydrostatic pressure. It finds its way through cracks, the joint where the floor meets the wall and around pipes. A sump pump collects that water in a pit and pumps it outside. If the pump fails, loses power or is too small, the water rises over the floor.

What if the floor drain is backing up?

Water or sewage coming up through a basement floor drain usually means the main sewer line is blocked. The floor drain is often the lowest opening in the house, so it overflows first. Stop running water, do not use chemical cleaners and call a plumber. Our drain cleaning service clears the line, and a camera shows the cause. Read our guide to sewer camera inspection cost for what to expect.

What if it is a plumbing leak under the slab?

If water appears in dry weather, the meter moves with everything off, or a spot on the floor feels warm, a pipe under the slab may be leaking. Our guide on what a slab leak is explains the signs, and professional detection can pinpoint it without breaking up the whole floor. The EPA's WaterSense program estimates the average household's leaks waste more than 9,300 gallons a year, so a meter check is worth doing either way.

How do I fix each cause?

Cause	Fix
Sump pump failed	Repair or replace the pump; check the float and check valve
Pump overwhelmed	Larger pump or a second pump; check the discharge line
Power outage during storms	Battery backup pump
Floor drain backup	Clear the main line; camera inspection
Pipe leak under the slab	Locate and repair or reroute
Gutters and grading	Extend downspouts, regrade soil away from the house

Will insurance cover it?

Virginia's Bureau of Insurance consumer guide says homeowners policies generally do not cover flood or surface water, and that insurers must offer water and sewer backup coverage, which may cost extra. A sudden pipe leak may be treated differently. Give your insurer immediate notice of a possible claim and protect the property from further damage.

Does the repair need a permit?

Pipe and sewer repairs that replace plumbing equipment generally need a Fairfax County residential plumbing permit. Your plumber should tell you before work starts.

How can I prevent basement water?

Test the sump pump before storm season.
Add a battery backup and a high-water alarm.
Keep gutters clean and downspouts directed away from the house.
Make sure the sump discharge line drains well away from the foundation.
Check the water meter monthly.
Keep the floor drain clear and have the sewer line inspected if it backs up.

Local note: Basements are standard in Oakton and Vienna colonials. Hillside homes in North Arlington and lots near stream valleys in Great Falls can see more groundwater after heavy rain.

Related reading: Learn whether a slab leak is covered by insurance, see how to prevent frozen pipes, and try the water meter leak test.

When should you call a plumber?

Call when water comes up through a floor drain, when the sump pump fails or cannot keep up, when water appears in dry weather, or when the meter moves with everything off.

Water coming up through a basement floor in McLean? Call (571) 760-4451 for sump pump and leak help from McLean Plumber Works.

Frequently asked questions

Why is water coming up through my basement floor when it rains?

Groundwater rises after heavy rain and pushes up through cracks, joints and the gap where the floor meets the wall. This is called hydrostatic pressure. A sump pump and drainage system manage it.

How can I tell if it's a plumbing leak or groundwater?

Groundwater usually shows up during or after rain. A plumbing leak shows up in dry weather too, often with a moving water meter, a warm spot on the floor or a higher bill.

Is water coming up through a floor drain a sewer problem?

Often. If water or sewage comes up through a floor drain, especially when fixtures are used, the main sewer line may be blocked. Stop using water and call a plumber.

Does homeowners insurance cover water through the basement floor?

Virginia's Bureau of Insurance says flood and surface water are generally not covered by homeowners policies, and sewer or drain backup coverage is offered separately. Check your policy.

Can I seal the cracks myself?

Sealing small cracks may help with dampness, but it rarely stops water under pressure. Find and fix the cause first: groundwater, a failed sump pump, a drain backup or a pipe leak.

Water Coming Up Through the Basement Floor: Causes and Fixes