I'm fitting a portable AC into my workshop to take the edge off summer temperatures. For convenience, to make sure it works before bashing a hole in a brick wall, and to confirm it will help, I am temporarily piping the outlet to a pre-existing soffit vent.

The AC unit has some 150mm (6 inch) hose built in, but its odd. The twist is "left hand thread" and that's how it twists onto the unit. This hose is also quite stiff, and clicks between "expanded" and "compressed" Seems to be made of a stiff white plastic.

I can buy "right hand thread" hose but the wire support doesn't connect to the unit because the thread is backward. This hose comes in two materials, an aluminium (aluminum) foil with quite wide thread spacing, and a soft PVC plastic that is very floppy.

Own work

Diameter is not an issue, its the material and the twist that are different.

The air temperature of the exhaust is around 35 degrees C according to my IR gauge. So I wonder if the PVC plastic is up to this.

I see there are insulated ducts available too.

What ducting do I need for my portable AC? Looking for some names or keywords.

The existing pipe is absolutely a spiral hose. It has a positive click feel, like a bendy straw (but those aren't spiral)

  • are you certain that the AC unit tube is actually spiral?
    – jsotola
    Commented Dec 29, 2019 at 3:15
  • you could use hose that is for use with a clothes dryer
    – jsotola
    Commented Dec 29, 2019 at 3:16
  • @jsotola confirmed its spiral - the hose threads into the AC machine, and into a "funnel" at the other end. Its only 1.3 metres long, so I need to replace or extend it..... guessing that replacement will be cheaper than extending plus an extra joiner.
    – Criggie
    Commented Dec 29, 2019 at 4:03

2 Answers 2


We have a portable AC as well. Since the original pipe was too short, the only way to run the exhaust was to swap it out for the piping you have pictured at the top. It stretched over the original terminations at the AC unit and the window just fine. I held in place with duct tape. The pipe I used was 15' long compared to the original 6' pipe like you have. I was concerned about an increase in static pressure and how the unit would perform, but it did work very well on cooling the part of the house we needed with no issue.

"Threading" it on was not an issue, it was just pulled straight on and brought a wire or 2 over the nibs that acted as threads for the original pipe.


Upshot - the floppy tube gets hot and starts deforming. Its obviously not capable of carrying warm air from a portable AC. My temperature sensor says ~40 degrees on the outside.

The fixed tube doesn't seem to care - it is what came with the AC and copes with the heat fine.

The aluminium tube copes with the heat too, but it leaks the heat back into the room I'm cooling, probably because of the thermal properties of the metal foil. Also this one is not durable - it develops holes easily. A permanent installation in a ceiling would be fine, but not for something that gets packed up and moved, or bumped around.

In the end I found some more of the more-rigid hose like what came with the AC unit, and that's working well enough. The portable AC knocks the top off the temperature, but can't hold a candle to a proper split through-wall system professionally installed.

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