My air exchanger drain hose in a recently purchased home (in Québec, Canada) has mold growth, is kinked, sags below the drain mid-way and obviously needs replacement.

The PVC at the left is the excess drain for my whole-home bypass humidifier, which all goes to a condensate pump behind the furnace.


  1. Can I replace the exchanger drain hose with PVC/Pex? Or is there a good reason/code to keep it as clear hose (which is primarily what I've seen when researching)?

  2. The red circle is presumably a vent to allow the condensate pump to operate effectively. Is it normal to feel air blowing out of that when the HVAC blower runs? It seems logical since there's positive pressure at the humidifier pad which drains into this system, but I thought I'd check.

air exchanger drain

1 Answer 1


Clear vinyl tube is nice because it allows the home owner/resident to easily see whether their condensate drain line is plugged or backing up, as you're doing now. I don't know of any code requirement for it, and in fact the vinyl tube might not meet code requirements if this had been in the USA. This is one spot where I wouldn't get tremendously worried about following the code precisely: just make sure the drain is working.

In my opinion the sag itself isn't a problem - some condensate drain lines include a trap, which is little more than a deliberate sag. Again, though, one needs to be sure that the condensate can actually flow through. You're right that the kink is a problem that needs to be resolved.

PVC is most commonly used for this application. PEX likely could work, but like vinyl tube may technically not satisfy code. PEX connections are relatively expensive, too.

The open end in the red circle would not be necessary for the pump operation - the pump normally sits in a small reservoir that's open to the atmosphere so no suction will develop. It does make sense that air would blow out of that open end, but I don't see any reason why it would be necessary that the end remain open.

  • Very detailed answer, thank you! For context, only suggested Pex because I have to replace some Poly B in a bathroom, so I thought this would be a good use of leftover (plus couplings, though). I intuited the same about clear pipe; in that case I'll probably go PVC and just add a cleanout tee/wye at the top.
    – msanford
    Dec 16, 2023 at 1:24

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