How do I keep a basement from flooding again?

Start with the roof water

A basement that has flooded once will flood again unless something about how water reaches the house changes. The first thing to change is the roof. When it rains hard, an average sized home can experience hundreds of gallons of runoff coming from the roof.^[1] Where that water lands decides whether it ends up against your foundation.

Three habits do most of the work. First, keep the ground sloping away. Land around your house should slope away from foundation walls.^[1] Ideally, a 5% grade should be maintained for a distance of ten feet around your home.^[1] That is about 6 inches of drop over 10 feet, and settled soil next to the foundation is the usual place it goes missing.

Second, keep gutters working. Gutters should be cleaned free of debris at least once a year.^[1] If you see spillover during a storm, the district's reading is that a spillover of runoff is an indication of undersized gutter system.^[1] Gutter cleaning from a ladder is a fall risk; read how often to clean gutters and hire it out if the eaves are high.

Third, carry the water away. Install a concrete or plastic splash block at the end of the pipe to direct flow away from the foundation wall and prevent erosion.^[1] Better still, downspout or sump pump extensions (non-perforated corrugated plastic pipes) can be attached to the downspouts to direct flow further from the house.^[1] Whenever you redirect stormwater, make sure it is discharged to a suitable area.^[1] Your neighbor's yard and the street are not suitable. See how to extend a downspout away from the foundation.

If you have a sump pump, prove it works

A sump pump is the last line of defense against groundwater, and it fails quietly until the night you need it. Wayne's manual for its submersible sump pumps says the pump should be inspected 3-4 times per year.^[2] The test is simple: pour a bucket of water into the pit to make sure the pump starts automatically and the water drains quickly once the pump is on.^[2] If it does not start, have it serviced or replaced.

Check the details around it too. Make sure the pump is plugged in to a working ground fault circuit interrupter (GFCI) outlet and the cord is in good shape.^[2] A tripped GFCI shuts the pump off without any warning. Watch a cycle and verify the discharge pipe is carrying the water to a point at least 3 ft. away from the foundation,^[2] or the pump is only recirculating water back to the wall. The same manual says to replace the tether switch every two (2) years.^[2] That is for that pump, so follow your own manual.

Power outages often come with the storms that flood basements. During extreme weather, electricity can go out, leaving a basement unprotected against flooding at the time it is needed most.^[3] A battery backup provides protection against power outages and ensures the pump continues to work regardless of electric status.^[3] See how to test a sump pump and whether you need a sump pump in the basement.

Keep storm water out of the sewer

Do not tie your drains into the sewage system to get rid of rain. Spotsylvania County says improper connections to a private sanitary sewer lateral are a problem: improper connections include roof downspouts, groundwater sump pumps, foundation drains, and drains from window wells, driveways, etc.^[4] That extra water can overload the public sewer and cause overflows. The county also advises you to keep your cleanout cap on and in good shape.^[4]

Window wells and floor drains

Window wells can funnel water straight into a basement. Fairfax County's flood program says a ground floor or basement window well should have a central drain,^[3] but installing a new drain requires soil excavation and either reinstalling or replacing the window well liner.^[3] That is a contractor's job. Floor drains that connect to sewer laterals can back up too; the same program says disconnecting or plugging these drains can reduce the chance of sewer backups occurring,^[3] but have a plumber decide whether yours can be plugged safely.

Insurance is part of the fix

No amount of grading makes a basement flood-proof. Ready.gov is blunt: Homeowner’s insurance policies do not cover flooding.^[6] Flood coverage comes from the National Flood Insurance Program or a private policy, and it typically takes up to 30 days for a policy to go into effect,^[6] so buy before the storm. Ask your agent separately about sewer and sump backup coverage.

Stop and call a pro if

• Water comes in through the floor, cracks or the wall-floor joint even with gutters and grading fixed. That points to groundwater pressure; a drainage or waterproofing contractor should look at it.
• The sump pump will not start, runs constantly, or is hardwired. A pump wired directly to the panel is electrician work.
• Sewage comes up through a floor drain. Do not use the space. Call a licensed plumber.
• The fix means digging or regrading. Installing a window well drain needs soil excavation,^[3] and Virginia 811 advises contacting Virginia 811 to request utility line markings before you dig.^[5]
• A new sump, battery backup or drain needs a permit. In Fairfax County, approved practices may require applying for and the issuance by Land Development Services of building and/or mechanical, electrical, and plumbing permits.^[3]
• Water has already come in. See how to dry out a wet basement after a leak, and when you need a pro to dry out a house.

Getting help in Virginia

For the cause outside the house, why a yard floods when it rains is a good next read. Browse restoration answers or restoration businesses on Loclis.

When you are ready, describe the problem and local pros can quote it.