Installing a Basement Sump Pump

Basement sump pump in concrete floor

The Spruce / Margot Cavin

Installing a sump pump can be an effective way to keep water from accumulating in a basement. The pump is set in a basin, or a sump pit, located at the lowest spot in the basement floor or where water first accumulates. Sump basins, which can be purchased at home centers, are most often made of plastic or fiberglass. As the water level beneath the basement floor rises, it fills the pit and activates the pump, causing the water to be discharged to the outdoors. Once the water level falls, the pump shuts off. The sump pump turns on and off automatically through a float device on the pump; it operates much like a toilet in this regard, activating when the float device rises with the water level in the pit, shutting off once the water level drops.

If your basement has occasional water problems, a sump pump can help remedy the problem and is relatively inexpensive and easy to install. But keep in mind that installing a sump pump will not address the source of your water problem; that is, it won't stop water from coming in. And if your basement is seriously flooded on a regular basis, a sump pump may not be the best solution.

To be entirely effective, a sump pump is best installed in conjunction with a drain tile system. This system features an in-ground trench dug around the perimeter of the basement, which is covered over with concrete after construction. Containing gravel and a porous plastic pipe known as drain tile, this invisible trench funnels water from the edges of the foundation to the sump pit, where the sump pump can then eject the water out of the basement. Without a drain tile system, a sump pit and pump is most effective if it can be positioned in the precise low spot in the basement where water naturally collects. While installing a sump pit and sump pump alone can be done by an energetic DIYer, installing an entire drain tile/ sump pump system is a major undertaking that not many DIYers will want to tackle themselves.

Types of Sump Pumps

There are two types of sump pumps commonly installed in houses. Submersible pumps are fully concealed in the sump pit, while pedestal pumps are only partially concealed, with the motor resting above the water. Pedestal sump pumps tend to cost a bit less than submersible models, and they are easier to repair and maintain. But submersible pumps are quieter and therefore are a better choice for living areas.

Sump pumps usually come with long cords, allowing you to plug them into a receptacle protected by a ground fault circuit interrupter (GFCI). Do not use an extension cord with a sump pump unless it matches the recommendations of the pump manufacturer.

Plumbers usually install sump pumps, but a motivated DIYer can also handle the job. If you want to install your own sump pump, plan to spend $300 to $500 for materials and the better part of a weekend for the installation.

Buy a Quality Pump

Sump pumps typically last about 10 years, but better models with more powerful motors often have a longer life expectancy. Look for a model with a good warranty. If power outages are a problem in your area, you may want to invest in a backup battery system that will keep your pump operating even if the power goes out. After all, a heavy storm is precisely when sump pumps are most necessary.

Digging a Sump Pit

To be effective, a sump pit needs to be at the precise location where water normally collects on the basement floor. Carefully observe where you have water collecting after heavy rains, and mark this area on the floor.

You will need a jackhammer to break through the concrete. Electric jackhammers are usually available at rental stores or in the tool rental department at home centers. They are easy to use and can be plugged into regular household outlets. Be sure to get a flat spade bit to use with the jackhammer.

Set your sump basin upside down on the floor, then draw a circle about 4 to 6 inches outside the perimeter of the basin. Be sure to stay at least 10 inches from the walls to avoid the foundation footing. Use the jackhammer to break through the slab along the outline. Make sure to wear hearing protection and a particle mask while doing this work–it is a very loud and messy job.

With the concrete out of the way, dig the hole to the required depth. You will want the top of the basin to be exactly flush with the floor surface. Set the sump basin in the hole, and fill the gaps around the perimeter with loose gravel. Level the gravel in the excavation to level about 1 inch above the bottom of the floor slab then fill the remainder of the excavation with concrete. Smooth the surface of the concrete level with the surrounding floor, using a trowel, and allow it to set for at least 24 hours.

Installing the Sump Pump

Set the sump pump in the basin as directed by the manufacturer. In some cases, it may be recommended that you add gravel to the bottom of the sump pit and/or set the pump onto a concrete paver to raise it off the bottom of the pit.

Install a check valve onto the outlet of the pump. Check valves typically are installed with hose clamps so it is easy to remove the pump for servicing or replacement.

Completing the Discharge Pipe

Connect a short length of PVC pipe to the open end of the check valve, then glue a 45- or 90-degree PVC elbow to the short pipe to route the discharge piping toward the basement foundation wall. Add another length of pipe, followed by another 45- or 90-degree elbow at the wall. Install a vertical pipe from the elbow to the rim joist above the foundation wall.

Using a hole saw, drill a hole through the rim joist and the exterior siding to route the discharge pipe through the wall. Continue the piping with a 90-degree elbow and a straight horizontal pipe running through the hole in the rim joist.

Once outdoors, you can route the pipe back down to the ground and out to a suitable drainage point so the water flows away from the house. Seal around the hole in the rim joist with caulk.

If the grade is not suitably sloped away from the house, you may need to install a dry well outside to handle the sump pit discharge. A dry well is a deep pit filled with gravel which allows water to gradually be absorbed into the surrounding soil. If using a dry well, make sure to position it a suitable distance away from the foundation. Do not run the discharge into a sewer unless you are sure this is permitted by the local building code.

Sewer Discharge Usually Prohibited

A very common error is to discharge a sump pump into a basement utility sink. In most communities, this is strictly prohibited, as rainwater and groundwater can overwhelm a municipal sewer system. Always follow local guidelines for discharging a sump pump.

Running Your Pump

Plug the sump pump into a GFCI-protected receptacle. Fill the basin with water, and test the pump for proper operation. It should turn on automatically when the water reaches a level that lifts the float on the pump, and it should turn off when the water level drops. Adjust the float level of the pump as directed by the manufacturer.

From time to time, you will need to clean debris out of the basin. If your pump is not activated very often, periodically test it by pouring some water in the basin. Make sure to unplug the pump from the power supply before cleaning the debris out of the pit.