I have a wall-mounted AC unit. Specifically, a Fujitsu ASTG24LFCB. Recently water started leaking from the interior portion of the unit. I followed the instructions in this video to troubleshoot the problem. The process mainly involved tilting the unit up and checking for any issues/blockages in the drainage tube.

I didn't see any issues, but noticed that the drainage tube seemed to travel upwards after leaving the unit and entering the wall cavity. Thinking that could be a cause of the leak (because I assume the water can't drain uphill?), I started maneuvering the tube back through the hole in the wall to position it more in the downward direction. I was then surprised to discover that the drainage tube comes to an abrupt end. As in, it does this:

enter image description here

I don't see how this could possibly work? But not knowing what else to do, I fed the tube back into the wall cavity in the downwards direction, and the unit no longer leaks.

However, there's no longer any water being discharged on the exterior side of the wall. I think the reasons for that are obvious. Less obvious is an explanation for how the water ever reached the external drainage tube in the first place (which I'm positive it did, in the past)?

Is it common (or even valid) for an aircon to be installed like this? If not, how can proper drainage be restored? And what sort of damage will having the unit draining into the wall cavity cause, over what sort of timeframe?

  • What's up with that tape? Because the upper section of tube appears to be slightly different drain type/color than the lower section of tube. Do you see any evidence of tape on that downslope end? I'm wondering if the lower section was "spliced in" during the initial install, for some reason, and whether it became detached over time. If so, after detaching, it might have slightly recoiled upward, eliminating the sloping condition and creating the circumstances necessary for the leak. The drain tube should outlet somewhere, hopefully on the other side of that wall, can you find it? – elrobis Dec 19 '17 at 20:05
  • I believe you're correct that the tape is joining two separate tubes together. There's nothing obvious to suggest that the end of the tube used to be taped to something else (though that doesn't mean that it wasn't). There's an outlet on the other side of the wall, yes. Prior to when the leak started it would discharge water when running the unit. Since then, nothing. – aroth Dec 20 '17 at 0:16

First, the damage that can be caused is severe. Don't run the unit until this is fixed. Here's the deal, these units are indeed installed on the wall, typically high up on the wall relatively near the ceiling. The tubing package is designed to exit out of the back of the unit and down the outside of the wall the unit is installed on. Here is the key though: As soon at this tubing package, (the refrigerant lines, the electrical line and the drain line)as soon as they exit the back, at the very same time this package must drop significantly in elevation. The first hole in the wall, through the surface the unit is hung on must be centered a good inch to two inches below where this package is coming off the back of the unit. Right from the start this drain line must fall down and away for the condensate collection tray. The second hole, the hole in the exterior siding of this same wall should be a good 4" to 6" below the first hole. Then the tubing package must extend straight downwards for a good 3+ feet before turning in any other direction. That drain line must continually slope downward from the time it leaves the collection tray until the time it drains on the ground. At no time can this drain line run horizontal or slope up even for a short distance.

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