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Q.The municipal storm drainage system in our city shares pipes with the sewer system. During heavy rainstorms, water backs up from the municipal drain line into a customer’s basement floor drain. Is there any type of check valve that can be installed in the drain line to prevent this?

A.Master plumber Rex Cauldwell responds: First of all, be sure that the local water department and building authorities are aware of the problem and see if they can propose a solution.

If the local municipality is unable to help, you have two choices. In either case, you’ll need to cut open the floor slab. If all you want to do is stop stormwater (or worse) from coming into the basement via the floor drain, you can install a backwater valve in the drain line. Backwater valves are available for about $40 to $60 from Canplas Inc. (888/461-5307) and Oatey (800/321-9532; www.oatey.com). Most backwater valves are available with sleeves and access panels so that they can be installed under concrete and still be accessible for maintenance.

If you want the basement to drain even during a heavy rainstorm, you’ll need to remove the floor drain and install a sump pump. Remove the existing drain, but leave the trap. Dig a hole for a plastic bucket or sump kit, and then install a submersible sump pump. Connect the sump pump’s two-inch discharge connection to the existing drainpipe under your slab, using watertight threaded or glued fittings. Since the sump pump includes a check valve in its discharge fitting, stormwater will no longer be able to back into the basement from that location. The sump pump will be able to pump out under pressure any liquid that flows into the sump, even when the utility drains are full.