A sump pump is the last line of defense for a basement that takes water. It sits in a pit at the lowest point, and when the water rises, it pumps it out before the water reaches the floor. Installing one is a weekend job for a handy homeowner — digging, plumbing, and one electrical outlet. The digging is the hard part; the pump is the easy part.
Before you dig: find the lowest point of the basement floor — that is where the water collects, and that is where the pit goes. Check for buried pipes and wires before you break the floor: call 811 or your local utility locator. And check the discharge route: the pipe has to run outside and downhill, away from the house, or the water comes right back in. Water coming through the wall has its own diagnosis — the water through the wall guide covers how to find the entry point.
Mark and break the floor. Mark the pit location — a circle the size of the basin, at the lowest point of the floor. Break the concrete with a jackhammer or a sledgehammer and a chisel. Wear eye and ear protection: concrete chips fly, and a jackhammer is loud. Keep the broken pieces for the patch later.
Dig the pit and set the basin. Dig the pit about 6 inches deeper than the basin and 6 inches wider all around. Put 6 inches of gravel in the bottom, set the basin in, and fill around it with gravel. The gravel drains water into the basin — and it keeps the basin from floating when the water table rises.
Set the pump and the float. Set the pump in the basin on a brick or a paver — never flat on the bottom, where silt clogs the intake. Set the float switch so the pump starts when the water is a few inches deep and stops before the basin empties. A float set too low short-cycles the pump; a float set too high lets the water reach the floor.
Run the discharge pipe. Run the discharge pipe from the pump, through the rim joist or the wall, and outside — downhill, away from the house, at least 10 feet from the foundation. Put a check valve in the pipe near the pump: it stops the water from flowing back into the pit when the pump stops. Without a check valve, the pump runs twice as often.
Plug it into a GFCI outlet. Plug the pump into a GFCI outlet — never an extension cord, never a regular outlet near water. If there is no GFCI outlet near the pit, an electrician installs one: the outlet is the electrician's job, not a DIY job. A pump that loses power in a storm is a pump that does not work — the interior vs exterior waterproofing guide covers which system you need.
Test it. Test it: pour buckets of water into the pit until the pump starts. It should empty the pit and shut off, and the check valve should hold — no water flowing back. Test it again in a month, and test it before every storm season. Paint stops damp, not leaks — the basement wall waterproofing guide covers what paint can and cannot do.
Most homes need a 1/3 horsepower pump — it moves about 2,000 gallons an hour, which handles a normal storm. A 1/2 horsepower pump moves more, and it is the choice for a basement that floods fast or a house with a high water table. Bigger is not better: an oversized pump short-cycles — it starts and stops too often, and the motor wears out faster.
Never discharge the water next to the foundation — it comes right back in. Never skip the check valve — the pump runs twice as often without it. Never plug the pump into an extension cord — it is a fire risk and a shock risk near water. And never install the pump without a GFCI outlet: water and electricity in the same pit is the combination that kills.
DIY: roughly $200–$500 for the pump, the basin, and the pipe. Hired out: roughly $1,000–$2,500, depending on the floor and the discharge route. A battery backup adds roughly $300–$600.
At the lowest point of the basement floor — that is where the water collects. If the basement has no obvious low point, the pit goes near the wall where the water comes in.
Yes, if the power goes out in storms where you live. A pump without power in a storm is a pump that does not work — and the storm is when you need it most.
Every month, and before every storm season. Pour buckets of water into the pit: the pump should start, empty the pit, and shut off — and the check valve should hold.