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Fix a basement that floods

We'll help you stop active water, identify the source—sump pump, surface drainage, or plumbing—and fix it or tell you when to call a pro.

Troubleshooting · Home maintenance
30–90 min
What you'll need
  • Flashlight
  • Main water shutoff location (know before you need it)
  • Bucket or wet-dry vacuum (if removing standing water)
Step 1 of 12

Quick triage — pick your path

Quick triage — pick your path

Choose the option that matches what you see. You can jump straight to that section.

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Steps

Goal: Stop active water, identify the source, then fix it or call a pro.

  • If water is flowing now, shut off the main water supply for a pipe burst. If water rises from the floor, check the sump pump. If you smell sewage, call a plumber.
  • Good: Water stops or slows. Proceed to Identify when the water appears.
  • Bad: Water continues—call a plumber for sewer backup.

Stop water first

Goal: Stop or slow active flooding before diagnosing.

  • Shut off the main water supply if a pipe burst or leak is the source. Locate the main shutoff (usually in basement, garage, or at the street). Turn it clockwise to close.
  • If water rises from the floor, check the sump pump. Confirm power, GFCI, and that the float switch moves freely. See fix-sump-pump-will-not-run.
  • If you smell sewage, do not use plumbing. Call a plumber.
  • Good: Water stops or slows. Proceed to Identify when the water appears.
  • Bad: Water continues—call a plumber.

Identify when the water appears

Goal: Narrow the source based on timing.

  • Does the water come after rain or storms, or at any time? After rain points to groundwater, surface drainage, or sump pump issues. Anytime points to a plumbing leak or sewer backup.
  • Good: You know the pattern. Proceed to Sump path (after rain) or Plumbing path (anytime).
  • Bad: Unsure—check both paths.

Sump path

Goal: Fix sump pump issues when water comes after rain from the floor.

Surface water path

Goal: Fix gutters and grading when water comes after rain from walls or windows.

  • Check that downspouts are connected and direct water at least 4–6 feet from the foundation. See fix-downspout-is-disconnected.
  • Check grading—the ground should slope away from the house. Add soil at least 1 inch per foot for 5–10 feet if needed.
  • Good: Water flows away from the foundation. The basement stays dry after rain.
  • Bad: Gutters and grading are fine but water still enters—check foundation cracks or call a contractor.

Plumbing path

Goal: Find and fix plumbing leaks when water appears without rain.

  • Use how-to-find-water-leak to locate the leak. Check the water meter with all fixtures off. Inspect the water heater, supply lines, and visible pipes.
  • Good: You found and fixed the leak. The basement stays dry.
  • Bad: Meter moves but you cannot find the leak—it may be under the slab. Call a plumber.

When to get help

Call a plumber for:

  • Sewer backup (water from drains, sewage smell).
  • Slab leaks or leaks you cannot find.
  • When you are not comfortable with plumbing.

Call a contractor for:

  • Foundation cracks (water intrusion).
  • Major regrading.
  • Installing a new sump system.

Never work in standing water with electrical appliances plugged in. Turn off power at the panel if the area is flooded.

Verification

  • No standing water after rain or heavy use.
  • Sump pump runs when the pit fills and shuts off when empty (if you have one).
  • Downspouts direct water away from the foundation.
  • Ground slopes away from the house.
  • No plumbing leaks (meter stable with all fixtures off).

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Stop water Shut off main if pipe burst; check sump pump if groundwater.
  2. Identify source After rain vs. anytime—narrows to sump, surface water, or plumbing.
  3. Sump pump Check power, float, discharge. See fix-sump-pump-will-not-run or fix-sump-pump-runs-constantly.
  4. Surface water Check gutters, downspouts, grading. See fix-downspout-is-disconnected.
  5. Call a pro Sewer backup, slab leak, foundation cracks, or new sump installation.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • When the water appears (after rain vs. anytime)
  • Whether you have a sump pump and its status
  • Gutter and downspout condition
  • Whether water has sewage smell
  • Steps already tried

Is there standing water in the basement right now?

If water is active, stop it first. If not, identify the source before the next rain.

If water is flowing from a pipe, shut off the main water supply. If water rises from the floor, check the sump pump. If you smell sewage, call a plumber. Good: you have stopped or slowed the water. Bad: water continues—call a plumber for sewer backup.

Yes No

You can change your answer later.

Stop water first

Shut off the main if a pipe burst. Check the sump pump (power, float, discharge) if water rises from the floor. Call a plumber if the water smells like sewage. Once water is stopped, proceed to identify the source.

Done

Does the water come after rain or storms?

After rain points to groundwater or surface drainage. Anytime points to plumbing or sewer.

Recall when the water usually appears. After rain: sump pump, gutters, or grading. Anytime: plumbing leak or sewer backup. Good: you know the pattern. Bad: unsure—check both paths.

Yes No (anytime)

You can change your answer later.

Does water come from the floor or from walls/windows?

Floor water is usually groundwater (sump). Walls/windows suggest surface water (gutters, grading).

Check where the water enters. Floor: groundwater—sump pump or drainage. Walls/windows: surface water—gutters, downspouts, grading. Good: you know the entry point. Bad: both—check sump and gutters.

Floor Walls/windows

You can change your answer later.

Do you have a sump pump?

A sump pit is a hole in the floor with a pump. If you have one and water comes from the floor, the pump is likely the issue.

Look for a sump pit (round or square hole in the floor). If you have one and the pit has water, check the pump. If the pump does not run, see fix-sump-pump-will-not-run. If the pump runs but water still rises, see fix-sump-pump-runs-constantly. No sump: you may need one—call a contractor.

Yes No

You can change your answer later.

Is the sump pump running when the pit has water?

If the pit has water and the pump does not run, the pump has failed. If it runs but water still rises, it may be undersized or the discharge may be blocked.

Check the sump pit. If water is present and the pump does not run, see fix-sump-pump-will-not-run. If the pump runs but water keeps rising, see fix-sump-pump-runs-constantly.

Yes No

You can change your answer later.

Sump runs but water still rises

The pump may be undersized or the discharge line may be blocked. See fix-sump-pump-runs-constantly.

Done

Sump pump does not run

Check power, GFCI, and the float switch. See fix-sump-pump-will-not-run.

Done

Surface water — gutters and grading

Check that downspouts are connected and direct water at least 4–6 feet from the foundation. Check grading—ground should slope away from the house. See fix-downspout-is-disconnected.

Done

Water appears without rain — plumbing or sewer

Plumbing leaks or sewer backup can cause water anytime. Sewer backup often has a sewage smell.

If water has a sewage smell or backs up from floor drains, call a plumber—sewer backup. If no sewage smell, check for plumbing leaks—water heater, supply lines. Use how-to-find-water-leak to locate the leak.

Plumbing leak Sewer backup

You can change your answer later.

Find and fix the plumbing leak

Use how-to-find-water-leak to locate the leak. Fix the leak or call a plumber if it is under the slab or in the main line.

Done

Call a plumber or contractor

Call a plumber for sewer backup, slab leaks, or when you cannot find the leak. Call a contractor for foundation cracks, major grading, or installing a new sump system. Never work in standing water with electrical appliances plugged in.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why would a basement flood?
Common causes: sump pump failure (power, float, impeller), surface water from poor drainage (gutters, downspouts, grading), plumbing leaks, or sewer backup. Identify the source first.
What do I do if water is flooding my basement right now?
If water flows from a pipe, shut off the main water supply. If water rises from the floor, check the sump pump—power, float, discharge line. If you smell sewage, call a plumber immediately.
Can I fix basement flooding myself?
Yes, for sump pump issues, gutter and downspout fixes, and some plumbing leaks. Foundation cracks, sewer backup, and major grading work often need a pro.
When should I call a plumber or contractor?
Call a plumber for sewer backup, slab leaks, or when you cannot find the leak. Call a contractor for foundation cracks, major grading, or installing a new sump system.

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