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Our portable AC unit drains into a 3 gallon jug. When the jug is full, we empty it. This summer, the humidity has been bananas and the jug may be filling in as little as 2-3 hours. The fill rate is less predictable than I expected.

We worry about overflow if we're asleep or out of the house for a while. I want to prevent overflow without overengineering, if I can. I welcome suggestions at this point.

Here are simple solutions that won't work:

  • "Buy a bigger jug". We did, twice. We can't buy a taller jug at this point, as the outlet hose is gravity-fed from the AC condenser. A wider jug would take up a lot of floor space in our already-tiny apartment.
  • "Don't leave the AC running unattended". We have pets and without AC our apartment can get hotter than 40C, so we need to leave it running if we'll be out for a few hours.

Do they make small versions of basement sump pumps that could drain up into our kitchen sink?

Or maybe a water level sensor in the jug, which could control a switch on the AC's power plug?

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  • 6
    My unit has a "jug" which is built-in and has a full level detector which stops the unit from overflowing. Or, one can connect a pipe to a drain and it will run continuously.
    – Solar Mike
    Aug 15 at 17:59
  • Can you put this AC unit on a bench with a sink, such that the drain pipe can run into the sink? You could mould the pipe into a sink plug for additional sealing.
    – Criggie
    Aug 17 at 23:29
  • Thanks for your responses, everyone. I appreciate all of the suggestions. I'll try the condensate pump/float switch approach and see what I can do. Aug 18 at 13:19
  • Wouldn't the easiest thing to do be to run a hose to your shower drain?
    – Glen Yates
    Aug 18 at 21:21

6 Answers 6

16

The device you are looking to buy is (drumroll please) a condensate pump.

You should preferably also incorporate a float switch to kill the AC if the condensate pump fails to work or keep up for some reason, so the reservoir ("jug") does not overflow.

You could instead arrange to elevate the AC unit so it can gravity-drain to a sink.

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    That makes flooding is a distinct possibility. Better get two condensate pumps, then.
    – Ecnerwal
    Aug 15 at 18:25
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    Condensate pumps usually have auxiliary wiring which can be used to hook into the furnace's electrical system as a kill-switch in the event of failure. Not sure how easy this would be to achieve with a portable A/C unit.
    – MonkeyZeus
    Aug 16 at 13:51
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    A condensate pump and a float switch as suggested here can be installed in about 15 minutes and together cost much less than $100. This is definitely the way to go if you must keep using the bucket. Make sure the bucket is wide enough that the float switch can't get jammed between the side and the condensate pump. And tall enough that the float switch can work properly.
    – jay613
    Aug 16 at 19:27
  • I'll try this approach, thanks for the suggestion and the additions in the comments here, folks! Aug 18 at 13:26
  • @jay613 sure, if you don't have any overflow detection and just let it overflow if the pump fails. Aug 18 at 17:00
19

Avoid 1-hose portable units at all costs.

Those units are weirdly popular and trendy... and this is a mistake because of their horrible efficiency.

This is not bigotry. This is science.

Even if you are painted into a corner and are forced to use a "portable" unit, hold out for a 2-hose unit (which sends 2 hoses outside). Unfortunately they are not popular (most buyers are bad at physics), and you'll pay a premium - but you'll earn it back several times over in better efficiency.

Some 1-hose units can be "hacked" with duct tape and some dryer hose to become 2-hose units. However many cannot, because they use 1 common intake port for both process air and room air. I've seen people adapt those, but they had a home shop.

If this is still unclear, watch this video.

https://www.youtube.com/watch?v=_-mBeYC2KGc

Go window unit if at all possible.

Window units are also cheaper.

Yes, I know 1-hose portables are "popular and trendy", but if everyone else jumped off a cliff, would you?

The units are just terrible. They are inefficient, they require something be done with water, and worse, they suck humidity into the rest of your house making humidity even worse there, and causing mold.

Sell the thing to someone "trendy" and get an old fashioned window unit. If your window is narrow, shop for the smallest window units - they are surprisingly narrow and I've done 2 narrow windows successfully that way, including a casement window. (which required cutting and fitting some plywood and trim to fill the open space... On the casement we were able to stack two 5000 BTU units vertically, even. Or, you can get actual "casement" units that are taller than wide.

The window units get rid of water by simply dumping it on the "outside" side.

Why 1-hose portables are bad

Now they do make 2-hose units that are more efficient and do not suck heat and humidity into the rest of your house. However that does nothing about the water problem.

The 1-hose models suck in humidity into the rest of your house, because they are pushing air out of the room through that 1 hose. Where does replacement air come from? Every leak in your house. Most of which are in other rooms that aren't being air conditioned. So the humidity just comes pouring in.

In any case, they are ejecting conditioned (cooled, dried) air from your space, and drawing in unconditioned (hot, wet) air. Thus they are wasting conditioned air and making more work for themselves. This hurts efficiency badly, and US ratings of the machines have been revised downward to reflect this. You often see 2 numbers; the older number is what the unit would do if it were a 2-hose unit. You're paying the electricity for the difference.

By adding an aux tank, you broke the auto-shutoff

Our portable AC unit drains into a 3 gallon jug. When the jug is full, we empty it. This summer, the humidex has been bananas and the jug may be filling in 2-3 hours. The fill rate is less predictable than I expected.

The unit already had an internal tray, and an auto-shutoff when that filled. But like me, after emptying it 3 times in 6 hours, you said "this is for the birds". Unfortunately your method, with the jug, broke the auto-shutoff. So now you have an overflow problem.

I suppose you could go with a vastly larger bucket (42 gallon barrel, set the unit on top, spigot on the side to fill buckets to haul the water away? High enough on the barrel you can get a bucket under it.)

I don't see a good way to fix that.

Knowing what I do about hydraulics, I don't see a way to fix that. Affordable condensate pumps are not reliable enough, and wiring a high water shutoff would be absolutely insane given the risk of mixing water + electricity. How would you even attach it to a jug you take away to empty?

The best you could do is put a condensate pump inside the factory, built-in tray... so it never fills up, would be the idea. If the pump failed, the tray would fill and the shutoff would work normally.

But honestly -- this is complex stuff that is going to require actual engineering. Mistakes will be made and all of it will cost you money. Whereas, sticking a window unit in a casement window and coming up with some plywood and trim to seal it - well, it's annoying work, but it's straightforward work. So that is the way I would bet.

I have to say, having done that, life is easy street. I do zero maintenance on it, it just works.

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  • Comments are not for extended discussion; this conversation has been moved to chat.
    – BMitch
    Aug 18 at 1:34
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    Our building doesn't allow window units to be installed but thanks for the long response. I know that our hardware isn't optimal. We already own the unit and I'm trying to make the best of things. That's why I'm posting on the DIY Stack Exchange. "Get rid of it and buy something better" isn't the DIY spirit I'd hoped for. Aug 18 at 13:25
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    @Keegan Given where you are, isherwood's answer should have won. Everyone else is ignoring the consequence of pump failure, which should not be ignored, or proposing unsafe hacks to deal with it. isherwood's uses the unit's own overflow switch favorably to protect the added tank. As far as my answer, part of knowing how to DIY is knowing when not to - when you've just used too much duct tape and it's time for a new thing. Problems are cost of electricity running this old thing, and danger of a homebrew overflow limit switch. And complexity overall. Aug 18 at 17:13
13

Connect the auxiliary jug differently, such that it doesn't affect the shutoff mechanism in the primary receptacle.

I don't know what model you have, but you could presumably add a port to the factory container below the shutoff switch level, and run a level line to the auxiliary jug. This way, when the water level in both receptacles reaches the height of the float switch the unit is turned off.

This plan requires water-tight connections, but that shouldn't be too challenging with the right parts, such as threaded nipples, neoprene and rigid washers, and nuts. A valve and a quick-release connection on the tube would make emptying simple.

|=[] float sw.  |            |                           |
|               |============|<-- connecting tube        |
|               |            |                           |
|               |            |                           |
|               |            |                           |
|               |            |                           |
|_______________|            |___________________________|
  main tank                         auxiliary tank
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  • This should have won. However once OP has a condensate pump, they do not need the auxiliary tank anymore. Aug 18 at 17:16
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A new unit, such as a proper window unit as Harper describes, is really the best solution.

But one possible alternative if that isn't practical is to raise up the existing unit - e.g., build a sturdy wooden platform to get it a few feet off the ground. Then use PVC pipe (or similar, but I would avoid thin flexible stuff as it can too easily get kinked and/or clogged) to drain down (gravity is your friend) into a nearby sink, tub or toilet. Ideal would be a floor drain, but unlikely that you have one in the right place.

My central A/C has something similar. Original piping went with a slight slope around 3 walls of the laundry room to the laundry sink. That had issues, so I hacked together some PVC that goes much more directly to the floor drain. I'm fortunate - no condensate pump for me - I know too many people who have them but don't know what they do/how they work until they have big problems.

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A window or wall unit won't have this problem at all, as they discharge the condensate outside.

A different portable may be built in such a way as to require less frequent draining. Some pour the condensate back on the condenser and discharge the resulting steam into the exhaust hose. E.g. Delonghi. I actually have a Delonghi and do not experience difficulties with draining. I haven't drained this year. I drained more often when the device was newer. It shuts off automatically if there's too much water.

Putting the air conditioner on blocks can also allow you to get a taller jug or (as already suggested) access a drain. Pets may be a challenge though, as this would make the A/C less stable and easier to tip over. An actual platform might be more stable.

Put the entire A/C and the jug inside a tray. Perhaps put the A/C on blocks (e.g. bricks) inside the tray. Then if it overflows, it will overflow into the tray. Since the tray is underneath the A/C, it won't take up much more room than the A/C alone.

Do they make small versions of basement sump pumps that could drain up into our kitchen sink?

Yes, they do. Try "condensate pump for portable air conditioner". I get a number of relevant results. E.g. Little Giant. No idea on how well they work. Also may present challenges with pets.

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The overflow shutoff switch is important, because inexpensive condensate pumps do fail. DON'T mess with an external shutoff switch. This is electrically complex, and inevitably involves mixing AC mains with water. It is not practical to do this safely.

Once you get a condensate pump, having gallons of auxiliary tank is no longer necessary. Simply install the condensate pump so it draws out of the original tank. (a low voltage pump can even go in the tank). That means the built-in overflow switch will work again!

If the original tank is broken or gone, it will be worth buying or building a replacement tank. Since you have a condensate pump, size doesn't matter - the original tank was built to be as large as possible for the space available, but you don't need that - any piece of Tupperware will suffice.

It needs to be wide enough to get underneath both the drain and the overflow switch. It needs to be deep enough to fit the condensate pump. Use spacers underneath it to raise it to the right height so the overflow switch works.

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