• In this video, This Old House plumbing and heating contractor Richard Trethewey explains how to add a humidifier to a forced-air system.

    Steps:1. Screw the humidifier to a wall near the furnace.
    2. Cut away insulation from the duct using a utility knife.
    3. Position the hole-cutting template onto side of duct.
    4. Drill pilot hole through duct, then cut out hole with aviation snips.
    5. Secure the humidifier’s steam wand to the duct with self-tapping sheet metal screws.
    6. Attach steam hose to wand and to wall-mounted humidifier; secure hose with cable ties.
    7. Connect the flexible drain hose to steam wand and to humidifier.
    8. Run a copper drainpipe from underside of humidifier to sump pump or floor drain.
    9. Cut and solder a copper tee fitting into a nearby cold-water pipe.
    10. Run new cold-water copper piping to bottom the humidifier.
    11. Have electrician run electrical cable to humidifier and to room humidistat.
    12. Turn on water to humidifier.
    13. Install air-proving switch in duct.
    14. Set the upper limit of humidity on the high-limit switch.
    15. Set room humidistat to desired level of humidity in the house.
    See products and services in this episode.
    • Difficulty: Hard
      Requires professional installation by heating contractor and licensed electrician.

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      Video Directory

      Selected Topic/Section

      Tools List

      • utility knife
        Utility knife, used to cut duct insulation
      • drill
      • Aviation Snips
        Aviation snips, for cutting hole in sheet metal duct
      • propane torch
        Propane torch
      • Nut screwdriver

      Shopping List

      1. Wall-mount steam humidifier

      2. Copper pipe and assorted fittings

      3. Emery cloth

      4. Flux

      5. Lead-free solder