Water Around Furnace Means Clogged Condensate Drain

Get the water out of a clogged condensate drain with a few simple steps

If you notice water around the furnace, the condensate drain may be clogged with slime. Fix the problem with chemical tablets and a larger drain hose.

By the DIY experts of The Family Handyman Magazine

Clearing a clogged condensate drain

When you see water puddling around the furnace with the A/C running, you have a clogged condensate drain tube. Condensation from air conditioning coils contains bacteria that can form slime and clog the condensate pan drain tube. You can prevent slime and eliminate drain tube clogs in two easy steps. First, remove the drain tube and fitting from your A/C condensate pan. Toss them. Next, buy a package of slime preventing tablets (one choice is AC-Safe Air Conditioner Pan Tablets; sold at Amazon.com). Follow the package dosing directions and insert the tablets right in the drain pan (Photo 1).

Next, buy a 3/4-in. MIPT barb fitting, a small coil of 3/4-in. I.D. vinyl tubing, and several tubing straps. Then install the larger tubing (Photo 2). The pan tabs will reduce slime formation, and the larger-diameter tubing will enable faster condensate flow. That usually eliminates clogging for good.

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Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • Pan tablets
  • 3/4-in. MIPT barbed fitting
  • 3/4-in. I.D. vinyl tubing
  • Tubing straps
  • Small wood dowel