• This Old House plumbing and heating expert Richard Trethewey shows how to install an emergency backup sump pump

    1. Attach two 3-foot-long 2x3 cleats to the wall above the primary sump pump; fasten the cleats with 3-inch screws.

    2. Screw the backup sump pump to the 2x3 cleats using the mounting hardware provided. Be sure to set the float on the backup pump slightly above the height of the primary pump.

    3. Next, cut into a nearby cold-water line and run ¾-inch-diameter copper pipe down to the control valve on the backup sump pump. Solder each connection with a propane torch and lead-free solder.

    4. Unplug the primary sump pump. Then, drain water from the existing discharge pipe by using a slotted screwdriver to loosen the band clamp on the check valve.

    5. Cut into the into existing discharge pipe leading from the primary sump pump, and run a new 1½-inch-diameter PVC discharge pipe from the backup pump.

    6. Install a new check valve onto the backup pump, then use PVC pipe primer and cement to clean and solvent-weld together the plastic pipe and fittings.

    7. Disassemble the backflow preventer, then open the water valve to flush any solder or flux into a bucket.

    8. Fill the sump pit with water, plug in the primary pump and wait for it to turn on.

    9. Unplug the primary pump and raise the float on the backup pump by hand to simulate water rising in the sump pit. When the float reaches the appropriate level, the backup pump will kick on and drain the water from pit.
    • Difficulty: Moderate
      Requires basic plumbing skills, including soldering copper pipe

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      Tools List

      • hand saw
        Handsaw or circular saw,for cutting 2x3 cleats to length
      • drill
        Drill/driver, used to fasten 2x3 cleats to wall
      • Phillips screwdriver
        Phillips screwdriver, used to fasten the mounting hardware for the backup pump
      • propane torch
        Propane torch, for soldering copper pipe and fittings
      • tubing cutter
        Tubing cutter, for cutting copper pipe to length
      • pvc saw
        PVC saw, for cutting PVC pipe
      • pipe wrench
        Adjustable wrench, for disconnecting the backflow preventer
      • flathead screwdriver
        Slotted screwdriver, for loosening the band clamp on the check valve

      Shopping List

      1. Water-powered backup sump pump

      2. 2x3s, used as cleats to mount backup sump pump to wall

      3. 3-inch drywall screws, used to fasten cleats to wall studs

      4. ¾in. copper pipe, for delivering water to the backup sump pump

      5. Emery cloth, used to clean copper pipe and fittings prior to soldering

      6. Lead-free solder, for sweating copper pipe and fittings

      7. Flux, for applying to copper joints prior to soldering

      8. PVC pipe and assorted fittings, used to create discharge for backup pump

      9. PVC primer and cement, used to glue together plastic pipe and fittings

      10. PVC check valve, installed to ensure discharged water from sump pit only flows out

      11. Bucket, to catch water drained from backflow preventer