Sump Pump Installation, Testing, and Maintenance

Sump Pit Basics

If you're installing a new sump pump in a basement that doesn't have one, you need to create the pit first. Mark a location in the lowest corner of the basement or where water accumulates. Cut through the concrete floor with a concrete saw or a demo hammer with a chisel bit, then excavate a hole about 24 inches deep and 18 to 24 inches in diameter. Line the hole with a sump basin (a plastic or fiberglass liner with holes for water to enter).

The basin sits in the hole with its rim flush with the floor. Backfill around the basin with gravel. If you have an existing French drain or footing drain that terminates near this corner, connect it to the basin so the drain feeds directly into the pit. Otherwise, water enters through the perforated sides of the basin as the water table rises beneath the floor.

Choosing a Pump

Submersible pumps sit inside the basin, fully submerged when water is present. They're quieter, cooler-running, and take up less space than pedestal pumps. A 1/3 horsepower submersible handles most residential basements. If you have a high water table or frequent heavy pumping, step up to 1/2 horsepower.

Pedestal pumps have the motor above the basin with a long shaft reaching the impeller at the bottom. They're cheaper and easier to service since the motor stays dry, but they're louder and protrude above the floor. For most basements, a submersible with a vertical float switch is the best choice. Avoid tethered float switches in tight basins — they can snag on the basin wall and fail to activate.

Discharge Line

The discharge line carries water from the pump to the outside of the house. Use 1-1/2 inch PVC pipe. Run it from the pump's outlet, through the basement wall (core drill a hole or go through the rim joist area), and extend it at least 10 feet from the foundation. The discharge must slope away from the house and terminate where the water won't flow back toward the foundation.

Install a check valve on the discharge pipe just above the pump. The check valve prevents water in the pipe from flowing back into the pit when the pump shuts off. Without it, the pump cycles on and off repeatedly as water drains back from the pipe into the basin. ABS or PVC check valves with rubber flappers are standard. Install it with the arrow pointing away from the pump (toward the exit).

Electrical and Battery Backup

A sump pump needs a dedicated GFCI-protected outlet. Don't plug it into a shared circuit with other basement equipment — you don't want a tripped breaker from a shop vac or dehumidifier taking out your flood protection. The outlet should be above the pump so the cord hangs down rather than running across the floor.

A battery backup sump pump is a second pump that runs on a 12-volt marine battery when the power goes out. Power outages and heavy rainstorms often coincide, which is exactly when you need the pump most. Battery backup units sit beside or above the primary pump in the same basin and activate automatically when the water rises above the primary pump's shutoff level. They run for 5 to 12 hours depending on the battery size and pump frequency.

Testing and Maintenance

Test the pump every 3 months by pouring about 5 gallons of water into the pit. The float switch should activate, the pump should run, and water should exit through the discharge line. Check that the check valve holds after the pump shuts off — if you hear water flowing back into the pit, the check valve needs replacement.

Clean the pump intake screen or grate annually. Debris, gravel, and silt accumulate and restrict water flow to the impeller. Pull the pump out of the pit, clean the screen, and check the float switch for free movement. Inspect the discharge pipe for leaks at joints and for ice blockage at the exit point in winter. A frozen discharge line backs water into the basement, defeating the entire system. In cold climates, extend the discharge below the frost line or use a freeze-resistant discharge head.

Frequently Asked Questions