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In this video, This Old House plumbing and heating expert Richard Trethewey shows how to replace a faulty pump.


1. Use a PVC pipe cutter to slice into the existing PVC drain line running from the air-conditioner pump.

2. Attach a T-fitting to a new length of PVC pipe using PVC primer and cement. Then fasten a brass barbed fitting to the T-fitting.

3. Connect the new pipe to the existing PVC drainpipe using a coupling. Glue the connection together with primer and cement.

4. Secure the new drainpipe to a floor joist with a U-shaped pipe clip.

5. Connect the existing tubing coming from the air-conditioner pump to the end of the PVC pipe.

6. Run a new length of clear plastic tubing from the T-fitting back to the dehumidifier.

7. Force one end of the tubing onto the barbed fitting protruding from the T-fitting on the PVC drainpipe. Secure the tubing with a stainless steel hose clamp.

8. Clamp the opposite end of the tubing to the discharge port on the new dehumidifier pump.

9. Unplug and remove the old defective dehumidifier pump.

10. Set the new pump into the dehumidifier condensate tub, then plug the pump into a GFCI-protected electrical receptacle.

11. If necessary, pour water into the condensate tub to ensure the pump operates properly.