Preventing rain from entering the house through a window AC unit?

July 5, 2004 3:29 PM

Window AC unit and rain. How can you prvent rain from entering the house through a window AC unit? I think its coming in through the vents on the outside casement. Thoughts?
posted by evening to home & garden (11 comments total)

Can you build some shelter onto the wall above it (on the outside) so it's protected from the rain? A board and two brackets might be all you need, depending on your esthetics and what your wall is made from.
posted by scarabic at 3:35 PM on July 5, 2004

Check to make sure that the unit is slightly tilted downwards outside the window, so that any water coming into the casing runs out the back of the unit, rather than inside.
posted by dg at 4:04 PM on July 5, 2004

I don't think we can easily build something off the wall of the house as we have vinyl siding and I don't want to put temporary holes in the siding.

I will check the level of the unit, but the problem isn't so much from the bottom of the unit as it is actual rain drops falling through the unit into the house.

The front grate/panel that's inside will have water dripping down. I think it gets on the floor when the rain drops are hitting that front grate and splattering. Some of the vents on side of the casing are pointed upward, so its really easy for the rain to get in. I think, too, that it is bouncing on the unit, and falling into it. And just happens to be hitting at an angle that allows it to come inside.

If those deck umbrellas weren't so expensive, I'd just buy one and get it to hang over the AC, and use it on the deck when its sunny.

Maybe make a tent of somekind from outdoor fabric? But then how would I hang it? Ugh, I can't believe this is even an issue. How many people actually have this problem? One in a million??

(or maybe if I tilt it back more then it won't be as likely to do this?)
posted by evening at 4:29 PM on July 5, 2004

Perhaps adding some kind of flap or cowling to the unit itself would be easier. Without having it in front of me, it's hard to say, but you might be able to do interesting things with pieces of vinyl and/or galvanized tin plus some magnets, adhesives, metal strapping, or bolts.

I'm imagining taking a flat piece of tin, maybe 5'x2', folding it into a U-shape, and then fitting that over the top and sides of the unit. Strap or clamp it on, depending on what you have available.
posted by scarabic at 4:49 PM on July 5, 2004

Even just a plastic sheet, that you could secure to the window and around the back casing with duct tape, or whatever. You've got the leave the back side of the unit open, obviously, or it can't get the heat out of the house, but the all four outside sides and the window fit should already be pretty much airtight/watertight, just in principle, for good cooling.
posted by LairBob at 5:16 PM on July 5, 2004

The last one I had was equipped with: 1) a small roof covering 2.) a vinyl zip cover and 3) was tilted slighty down toward the outside. It was heartening to note that none of these remedies were effective and the interior wall below the unit was gloriously water stained. I did consider plugging all of the vents.
posted by tonebarge at 5:21 PM on July 5, 2004

Some of the vents on side of the casing are pointed upward, so its really easy for the rain to get in.
Probably a silly question, but is it possible that the casing has been installed upside-down? Normally those vents face downward to prevent exactly what is happening to you.
posted by dg at 6:41 PM on July 5, 2004

dg's question makes a lot of sense actually--a lot of larger window-mounted AC units actually have an outer casing that you slide off, and install in the window while it's empty and really light. Then you slide in the actual unit after the fact. I can't _imagine_ why you'd have side vents on an air conditioner (or just about anything meant for outside) point upwards.
posted by LairBob at 8:56 PM on July 5, 2004

I used to have this problem in an apartment where the landlord never cleaned the gutters, and failed to believe me, repeatedly, when I explained that this meant a torrent of water coming down the column of windows where my AC was located. (I had three or four incidents where the neighbors below complained about water damage, and none of them were in any way my fault. But see, there was a *history* of water problems coming from my unit. Assclowns.)

Eventually, though I tried various awning/deflector strategies, the only thing that worked was attaching a handle to the top of the unit that allowed me to pull it inside hastily. When it's raining, often you don't need the AC, at least. Oh, I also built in a spacer 2x2 on the sill, which helped it reach the correct height for the storm window, and drilled weep holes in the bottom of the storm window, which helped it drain if it would ever accumulate water. I also poly'ed the sill.

Also, are you sure it's rain? Many ACs use a pan which is intended to fill with water on very humid days, which water then gets tossed around with the fan, which helps with the physics of cooling. Many people post in various places that they drill holes to drain this pan, which by design usually eventually evaporates, and in the process drill through important parts of their AC coolant system. Anyway, leveling is important to keep that water where it's supposed to be.
posted by dhartung at 11:09 PM on July 5, 2004

1 - yes, I thought that maybe the casing was installed upside down too, but there are holes on the bottom that all you to screw a triangle as the foot support for the casing. it is also just a frame on that side -- so no bottom. nice, so you can screw on the casing from the inside. so there's no way it is upside down. why the vents are angled upward is beyond me.

2 - I'll check the angle today and see if changing it helps at all. I know it is not the pan at the bottom as the water first shows up running down the middle of the vent/grate inside. If it were the pan, it would only be at the bottom, right? But maybe changing the angle will make the water splash differently.

3 - Another site said that it is impossible for water to be splashing in, that they're designed so this doesn't happen. And maybe the gasket is installed incorrectly. Now I just have to figure out what the hell a gasket is :)

4 - I know our problem is at least in part that the gutters aren't clean. We've only been in the house 1.5 yrs, and not sure if anyone did it before us. So its on the list of things to get done. Yesterday we needed the AC when it was raining as it was so hot and muggy it was disgusting out. So no deflector strategy worked for you? [ sigh ]

Thanks for all the comments.
posted by evening at 5:34 AM on July 6, 2004

(If you're really wondering, a "gasket" is a compressed seal that runs all the way around the edge of an opening--like in one of those old Mason canning jars, where you've got a rubber ring running around the mouth of the jar, and it gets compressed by the lid when you screw it down.)
posted by LairBob at 7:28 AM on July 6, 2004