We have a condensate pump for the furnace that connects via 3/8" tubing and a U-bend into the main sewer line. Been working fine for 20+ years.

We are now getting a new water heater and it requires a condensate drain too. I have a pump for it and will need to also connect the pump output to the sewer drain. Can I simply T using a 3/8" barbed T connector into the same drain ingress that the furnace pumps to?

If not, what is the correct way to drain it?


Image shows the current condensate pump line connected to the main drain line

enter image description here.

1 Answer 1


The location you suggest is going to be the best suited. The U-bend is effectively a vapor/odor trap to prevent back-smell from getting through the tubing into your household. Any other location would require that you create a new U-bend to prevent those gases from returning via the new drain line. One could expect odors from one drain line returning via the other, but there's nothing to prevent that with the existing line running solo, so that would mean you don't have odors from the condensate. Ensure that the flexible tubing will not kink when connected to the T fitting and you're good to go.

  • Thanks for the response. My concern was that the two pumps would fight against each other, and water could be pumped from one into another. But after doing some reading, condensate pumps have stop valves on their outlets which prevent this. So I think I'm good to go. If my understanding is flawed, let me know. Thanks again!! Sep 24, 2016 at 20:25

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