How Does a Sump Pump Drain Line Actually Work?

When water fills the sump basin in your basement, the sump pump drain line is what gets it out. Your sump pump is on constant vigil against intrusion from ground water seeping up through the foundation or from an inundation elsewhere, such as a ruptured water supply line in the basement. As water fills the basin—usually an 18-inch diameter pit excavated into the basement floor—a float switch actuates the pump and water is discharged through the sump pump drain line.

Indoor Segment

• The indoor span of drain line is usually a 1 1/4-inch or 1 1/2-inch PVC pipe. It attaches to the pump outlet with a threaded connection to facilitate easy removal for regular maintenance like cleaning the basin.
• Most of the indoor segment is in a vertical orientation, usually mounted to an exterior basement wall. The drain line turns horizontal as it leaves the house for the outdoor discharge point, usually located in the backyard (most local codes prohibit diverting sump water into a household drain.)
• A check valve is incorporated in the sump pump drain line adjacent to the pump. Because the vertical span averages 13 feet in length before it turns horizontal, the drain line retains substantial residual water when the float switch shuts off the pump. The check valve prevents water from flowing backwards into the basin and repeatedly reactivating the pump.

Outdoor Segment

• The horizontal outdoor segment of the sump pump drain line may be rigid PVC pipe. Alternatively, to make routing to the desired discharge point easier, this segment may be a flexible hose.
• To prevent discharged sump water from seeping back into the basement, the discharge point is usually at least 10 feet from the home.
• The outdoor span of drain line should be on a downward grade to drain residual water that may freeze and obstruct the line.

At Sobieski Services, Inc., our goal is to help our customers in Delaware, Pennsylvania, Maryland and New Jersey learn more about energy and home comfort issues – especially HVAC and plumbing issues – so that they can save money and live in healthier, more comfortable homes.

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