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June 14, 2005

Sump Pump Helps Keep Water Out

A sump pump may be homeowners’ first line of defense against water getting into the basement.

Basement flooding often is the result of water building up in the soil around a home and seeping into the lower level. A sump pump can get rid of the water before it leaks into the basement.

Here’s how it works. Drain tile, which can be clay tile or perforated plastic pipe, collects the water that builds up around the house’s foundation and drains it into the sump. The sump is a hole about 2 feet in diameter that holds 15 to 25 gallons of water. When the water reaches a certain level, the sump pump turns on and lifts the water to ground level, then discharges it into a pipe that leads away from the house.

Sump pumps are available at hardware and home improvement stores.

The pumps come in two basic models: upright, commonly called pedestal, and submersible. Either will work well with proper maintenance, according to Tom Scherer, a North Dakota State University Extension Service agricultural engineer.

The pedestal model has the motor on top and the pump at the base, which sits on the bottom of the sump. The motor should not get wet. A ball float turns the pump on and off.

Submersible pumps are designed to be submerged in water and sit on the bottom of the sump. The on/off switch, which is attached to the pump, can be a ball float connected to an internal pressure switch or a sealed, adjustable mercury-activated float switch. The sealed mercury switch generally is more reliable than the pressure switch, Scherer says.

Either type of pump should have a check valve on the water outlet pipe so the water doesn’t flow back into the sump when the pump shuts off. Water flowing back into the sump from the discharge pipe can cause the pump to turn on and off more often than necessary, which can cause the pump to wear out faster.

A backup sump pump is another item homeowners should consider having. Battery-powered backup sump pumps also are available at hardware and home supply stores. People who travel extensively or are away from home for extended periods should have a backup sump pump in case the power goes out during a thunderstorm or heavy rainfall, Scherer says. Homeowners who have a backup sump pump should make sure the batteries are fully charged.

To test whether the pump is operating properly:

  • Make sure the pump is plugged in.
  • Remove the sump’s lid, if it has one, and use a flashlight to see whether the sump is clean and the pump outlet isn’t plugged.
  • Slowly pour about 5 gallons of water into the sump at the same speed that water normally would flow into the sump.
  • Watch the on/off switch’s action and listen to the pump.
  • Make the pump turn on and off at least twice.

“If something doesn’t work right, fix it as soon as possible,” Scherer advises.

A number of factors, including the area of drainage connected to the sump and the depth of the basement, determine the right size sump pump for a house. However, a one-third horsepower pump generally works for most houses, he says.

Homeowners should not pump the water into their septic system or basement floor drain. Pumping into the floor drain is illegal in many cities because it puts additional water into a city’s sanitary sewer system and can overtax it. The additional water also can damage septic systems.

Scherer says homeowners should discharge sump water at least 20 feet from their home in a way that the water will drain away from the house. They also need to make sure the water won’t run into window wells, a septic system drain field or a neighbor’s lot.

For more information about sump pumps, visit the NDSU Extension Service Web site at or contact your county Extension office.


Source: Tom Scherer, (701) 231-7239,
Editor: Ellen Crawford, (701) 231-5391,



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