What is a sump pump system?

Don Vandervort

Do you have a basement that, during a heavy rain, looks more like a swimming pool? Basement flooding is a common problem, particularly in houses situated on flat terrain where rain and snow melt have little chance for runoff. When the ground becomes saturated, ground water pressure builds, forcing water towards any path of little resistance. If the water finds cracks and fissures in your foundation walls or floors, it easily seeps in to fill the "pool"--your basement.

The answer to this problem is a sump pump system. Sump pumps have been keeping basement laundry areas, storage rooms and recreation rooms pond-free in many parts of the country for years. They were first used in the New England and Mid-Atlantic states and Great Lakes regions but as cities have grown, so have water-runoff problems. Now sump pumps are common wherever basement flooding occurs. In fact, many communities require a basement sump pump in all new homes.

What is a sump system?

A sump pump system consists of four major parts: a ground-water collection system, a sump tank, a pump and an outlet drain. Here's how they work:

Ground water is collected by drain rock and drain tile buried along the foundation (and, in some cases, under the floor). Drain tile carries the water to the sump tank (or two sump tanks, in a large house) that is buried in the basement floor.

The sump tank, also called a "basin," "crock," or "sump pit," may be made of clay, tile, steel, concrete, fiberglass or polyethylene. Though they vary in size, standard tanks are about 18 inches in diameter and from 2 to 3 feet deep. Normally, a tank is located at the low point of the basement. Most tanks have a hole in each side for incoming drain tile and all have a sturdy cover. When ground water fills the tank to a given level, a float or some other switching device activates a pump. (Though much less common, some pumps are controlled manually.) Many pump manufacturers sell polypropylene or fiberglass tanks custom-fitted to their pumps.

Standard sump pumps are electric, powered by household current. There are two main types: submersible and pedestal. A submersible pump is completely concealed inside the tank. A pedestal model has a column that protrudes up through the tank's cover; the motor is mounted on the column, above the floor level. Both types draw water in through a filter trap (this should be cleaned periodically). They pump water out through a discharge pipe and/or hose. As soon as an automatic pump empties the tank to a certain level, it's motor turns off.

If it's connected to a sewer, the discharge pipe has a check valve and may have an anti-siphon device to prevent back-flow. Or the discharge pipe may simply connect to a hose that carries the water well away from the house. Codes in most areas dictate where the water must be discharged.