Introduction: Building a (mostly) Self-contained Condensate Recycler.

Picture of Building a (mostly) Self-contained Condensate Recycler.

Here in Tucson, AZ, air conditioning is so vital that if you're renting, your landlord has to provide it by law. The relief is almost worth the high electric bills that come in the summer months, but one thing has always bugged me.

If you have a cooler, whether it's a compressor/condenser style or an evaporative, or swamp cooler, there is always going to be some waste water involved. During the 100+ season, this is especially true, and it can create problems like unwanted weed growth around your machine and possibly damage to your foundation. In addition, the tap water here is piped in from remote locations and it's finite. Waste is dumb when you can prevent it easily, so I looked around for materials to create a solution.

Step 1: Gathering the Parts

Picture of Gathering the Parts

I took a peek around the garage, and noticed I had what I needed. Your mileage may vary, of course. Scouring secondhand shops, yard sales, and classifieds should yield the parts without too much trouble.

I didn't take photos of the assembly process, because to be honest I was winging it and wasn't sure it would work. Here instead is a shot with the parts explained.

You'll need:

1. An aquarium or reptile tank. Mine's about 10 gallons. I picked one with a screen top to prevent mosquito breeding. You could probably adapt the design to a hooded tank, though.

2. A low volume fountain pump. This one still has the fountain attached, but you could hook tubing to a bare one and install it in any kind of fixure you could think of. If you are just using an aquarium, you might be able to use the existing filter system and hack it to add an output.

3. Heavy duty duct tape.

4. Access to a file or rotary tool.

5. An outdoor source of electricity.

Step 2: Putting It Together

Picture of Putting It Together

Hopefully it's pretty straightforward from the picture, but I'm happy to explain.

1. Find your condensate output. On an a/c unit, there will be a pipe coming from the house, usually near the compressor unit. On a swamp cooler, there will usually be a length of tubing. Position your tank so that it can receive the drip most effectively. The condensate will leak into the tank, slowly but quite surely. After a day or so, the tank will be nearly full. It's time to put that water to use.

2. Remove your screen, submerge the pump and make sure the output tube fits securely. Many of these have suction cups which will be helpful. Note that running a pump dry will damage it.

3. Modify the screen.

If you have a sliding screen use a file or rotary tool to carve out a pair of divots for the pump's power cord and the output tubing. I found that it produced a better fit, but didn't carve enough to prevent the tank from being useful in its original purpose. If you have a screen that clamps on, you could use pliers to give the power cord and tube somewhere to sit.

4. Position the pump so that it will flow back into your tank. In my case I found an easy hanging spot on the gas meter, and will probably secure it with wire.

5. Seal any gap between the screen and tank with duct tape. I prefer Gorilla tape because it has a longer life span outside.

You're done. Plug in your pump and you have a recycling fountain. Interrupt the flow with a bottle, and you have an easy way to water your plants.

Step 3: Good on You, You Just Saved Some Water From Oblivion (but Be Careful With It)

Picture of Good on You, You Just Saved Some Water From Oblivion (but Be Careful With It)

I'm using mine to water potted aloe plants, because let's face it, you can get a lot of little burns and cuts when you're figuring things out. I have also considered some kind of drip system for the plants that will eventually live in the tire garden I just started building, but that will require further experimentation. Naturally I want to look into rainwater harvesting as well because this only works on a small scale, but in the meantime I can re-use the water my cooler was dumping into the abyss and feel a little less guilty about having it on in the first place.

Please note: I do not intend to use this water for drinking, and I don't recommend you do it either.


For the curious, I just called a local HVAC shop and asked about the toxicity of condensate. I was told that it should be fine, because it's just water vapor collected from the air, a by-product of the cooling process and not involved at all with the freon. They said it was fine to use for watering plants.

Since then, I've been notified via comments that it's not the water I should worry about, but the path it takes to the collector. In my case, it's an old pvc pipe which has seen better days. In the collector, the water is exposed to air and sun, so it's essentially a bacteria farm. I've been warned about Legionnaire's Disease, and I'm sure it's not the only bug that could be growing in this water. Until I know for sure, I will be using this water only for decorative plants and not for veggies.

In the meantime, I've decided to simply divert the condensate, via pvc parts, into a homemade planter built from a used tire. I've transplanted aloe plants into fresh soil and I'll be monitoring them to see how they respond to the condensate. At least this way something's getting watered, the water doesn't go straight to my foundation, etc. One experiment begets another.

Thanks to everyone who's been giving me feedback and suggestions.


chuckr44 (author)2013-02-07

I collect air conditioner condensate year round. In July and August I can fill a 55g drum in about 30 days from condensate alone. I use that to water the flowers around my property.

RustyRoller (author)2011-11-29

All these comments were very interesting to me. Two years ago, I decided to add a piece of PVC pipe to the end of my AC condensate drain pipe, so that the water would travel further from foundation. Then, to shade AC from Florida sun, decided to plant what gets called Mexican sunflower around here ... had collected the seeds from dried flowers the prior fall.

Figured the condensate water would keep it well irrigated without me needing to think about it at all (I run my AC almost year-round, as I'm heat and humidity sensitive). I've had to cut the shrub back several times, as it grows and flowers up a storm ... last time, it got higher than roof before I fully realized it, and then a bad wind and thunder storm half-uprooted the plant.

So, I cut it all back to a few feet high, added some soil around the base, and ignored it. Several months later, the thing is thriving, in bloom yet again, and will need trimming by spring. The only direct water is from the AC condensate line (and occasional rain).

But would I even think of using this water for anything else? Not a chance!

phillipt (author)2011-04-12

I've seen some comments here and on other posts about Legionnaires' disease and thought I could contribute some information from a little, basic research.

Foremost, I don't pretend to be otherwise knowledgable about this topic except for the few hours I have spent reading Wikipedia articles, the CDC page about Legionella bacteria, and some other general internet searching. But, I think the info I have found can be helpful.

Wikipedia: Legionellosis

Wikipedia: Legionella pneumophila

CDC: Patient Facts, Legionella

Simple Facts

1) Legionella bacteria are (a) aquatic and (b) aerobic. So, they mostly form in water and can grow anywhere there is oxygen: water and air, for example.

2) Following that, infection occurs from breathing in the bacteria from a vapor or mist. Evaporated water from contaminated sources is the concern here, hence the issue about condensate from an HVAC system.

3) Most people exposed to Legionella are not infected. But if you do come down with an infection, it is serious and can be fatal. The symptoms are very much like that of pneumonia.

4) The bacteria are not spread from one person to another.

5) Legionella can also be found in amoebae in soil, compost, and potting mixes.


I think it's common sense that we are talking about two possible ways of Legionella being a problem in your garden. On one hand, we worry about it getting into the produce. On the other, as the above facts point out, we should also worry about the water, and the air around the water, that we are using from the HVAC system.

To address the first case, take a look at the range of temperatures affecting Legionella; this is available in the Wikipedia article. Compare these to common cooking temperatures.

If you are pairing veggies with meat, you will likely kill any bacteria including Legionella pneumophila. If you are steaming veggies, you almost certainly kill them considering it takes 212-F or 100-C to boil water; I'd assume the residual steam is similarly hot, though I don't actually know. Along the same line, if you are making soup or otherwise boiling the veggies for even just a few minutes, you will definitely kill the bacteria. I can't recall a soup recipe that doesn't call for bringing it to a boil and then simmering for at least 30 minutes. Anything above 151-F or 66-C will kill the bacteria within minutes. And 70-C or 158-F would lead to absolute disinfection.

On that note, though, I'm not real sure that plants would even sustain the bacteria. There was no mention of such instances in anything I read, which was much more than the above cited pages to be clear. Being aquatic, the bacteria "live" in water; being aerobic, they grow where there is oxygen. Aside from being "infected," the plant could not otherwise play the part of a reservoir or host for the bacteria.

Furthermore, I don't believe that the plants become "infected" as one of the most common hosts for Legionella pneumophila is an amoeba found in soil: Acanthamoeba castellanii. That's right, soil! In fact, it's possible that the bacteria are in soil, compost, and even potting mixes and can be kicked up into the air with dust, where you can breathe in the bacteria. We all garden with much of this, so I figure (1) the CDC must be correct when they say most people that are exposed are not infected and (2) it sure doesn't seem to be affecting plants.

The only concern that I can see remaining is with regards to the vapors from this possibly contaminated water as it evaporates from your garden, as opposed to being taken up by the plants.

FACT: this water, before being used for irrigation, is already being evaporated into the air around you -- the HVAC condensate outlet is already disposing of the water. Some seeps into soil (is it affecting your grass?) and some will no doubt evaporate (is that affecting you?)

Legionella have been shown to have an effect in communities and up to several miles away. If you don't already have an outbreak in your area, and I'm sure you would know about it, then it's probably just as safe to let that water evaporate from your garden as it is to let it evaporate from the ground around the condensate outlet.

It's not likely in your produce, but if you think it is, common sense guidelines for preparing food should take care of that.

It's not likely a problem evaporating from the water source because if it were, you wouldn't be reading this; you'd already be in the hospital with Legionellosis.

If an outbreak of Legionellosis should occur in your area, then go to back to plain old manual watering until all seems well again. Otherwise, I'm sure it's fine. I feel compelled here to reiterate that I'm no expert. 

biochemtronics (author)2008-08-25

Interesting Instructable! I have a question. Could the water be recycled by using it to help cool the smaller and hotter of the two freon lines that run between the condenser and evaporator? A container similar to a small gutter could be put around a short length of the pipe and the condensate water could drain into that container. The pipe is very hot and would surely completely evaporate the water in the container quite easily. My house has a crawl space where these pipes run so a container up to around 8 or 10 feet would be no problem at all to install. Even a piece of split PVC pipe could be used. The condenser water could help cool the pipe and the freon it is carrying thereby increasing the effeciency of the AC unit. Even a little cooling could help save some money.

godfish (author)biochemtronics2008-08-30

I've been an UA, Local 250 Union HVAC&R; Service technician for 20 years, and you are right that it would make scene to cool the hotter line coming from the condenser outside, however Air conditioning systems work on the Pressure Temperature relationship, Cooling the hotter line is called sub-cooling and does make a systems effeciency go up, WAY WAY up. and if you whir to over cool the line too much your indoor coil would make only ICE, blocking the air flow and costing you lots of money in loss of effeciency. SO if we throw the T&P; out of whack by over cooling the line, OR like I've seen many times on residential calls people hook up water hoses to spray water on the condenser outside, all that happens is you cost your self more money on your electric bill. The best thing to do is have your A/C unit serviced by an honest company, change your filter when you should and keep the whole system clean, that will save you the most money. Or better yet just turn it off, A/C is a luxury and not a necessity. And YES I work in PALM SPRINGS So Cal, where it gets 121 in the summer, if I can work out in the heat, you can sit in your home without A/C. ;P

BluTiger (author)godfish2010-07-21

godfish thanks for the info! I was just getting ready to mist my condenser with rain barrel water....

biochemtronics (author)godfish2008-08-30

godfish: Thanks for the information. I suppose it would be nearly impossible to determine if the 5 to 10 gallons of condensate water would cool the hot tubing too much so I guess this idea could help but is not very practical since the effect could over do it and actually cause problems. However, I am surprised by the fact that cooling the outdoor unit with a water hose can cause the indoor unit to freeze up, but I guess it does make sense now that you mention it. One more thing - I have to disagree with you on AC not being necessary. I know there was a time not to long ago when nobody had AC but as for me - I could not live here in South Texas without it. LOL No, seriously - considering how many seniors die every year from the extreme heat, I would think it safe to say that AC can even prolong some people's lives. I plan to make it well beyond 100 with the help of AC. I want to thank you again you for your professional opinion. That is the nice thing about this site. We backyard do-it-ourselfers can get advice and help from experienced professional like yourself. Thank you for taking the time to help us out. It is greatly appreciated.

skincage (author)biochemtronics2008-08-25

That's a great suggestion. Hopefully someone more versed in HVAC can answer your question fully. I am intrigued, in any case.

thermoelectric (author)skincage2008-08-28

I'm not that good with HVAC vut i used to work with a guy that installs them, If you have a look at the outdoor unit, if the connections are condensing water, it would just be a waste but if your refrigerator has the wire on the back, you could have the water move through pipes over them because fridges get colder, use more power and put off more heat. Hope that helps, if u need to know anything else just ask

If both of the connections on the outdoor unit are condensing water then the unit is probably low on freon and needs to be recharged. On a properly working unit the one of the pipes is cold and the other is very hot. I am suggesting using the water from the indoor unit to cool the one hot pipe running to the outdoor unit. Also, trying to water cool a refrigerator with coils on the back or underneath would require major modifications including elaborate drip pans, splash shields, and in most situations, a pump to get the water to it. This doesn't take into account the extra humidity such a setup would put into the room. I really do not think that would be very practical or efficient. And as for a refrigerator using more power than an central AC unit - there is no way. Refrigerators run on a 120 volt, 15 or 20 amp circuits. Central air conditioners run on 240 volt 30 amp circuits. Also an average size AC unit gives off around 4,000 to 6,000 BTUs of heat whereas a refrigerator only gives off a couple hundred BTUs at most.

TogetherinParis (author)2010-07-11

You can cut the bottom off a 2 liter coke bottle and screw it to an old hose to funnel condensate pipe drippings through the hose under your lawn's grass to your fruit trees. Dirt just loves bacteria that gets into the water along the way. The trees (or plants) keep their fruit sterile on the inside--that's why you should cut and eat fresh fruit if you change climates to avoid Montezuma's revenge. Rain is condensation, too. Of course, if you sprinkle the condensate water on the fruit itself (instead of just irrigating the roots as I do) you might be asking for trouble. The beauty of air conditioner condensation irrigation is that your garden gets more irrigation when the weather gets warmer. I just left the cut hose end in a depression under my tangerine tree and covered it over with some compost to keep it from evaporating away. Wow, I've never seen such a crop of fruit like we're going to have this winter! No pumps, just gravity flow, and it does the job spectacularly.

Madrias357 (author)2009-06-10

Well, the water's good for washing a car. First: It's free water. Second: your car won't care what it's washed in. Third: It's FREE water. Thereby, logic states it's good for washing cars, clearing a sidewalk of dirt and debris by means of pressure washer, watering small decorative plants and trees, and generally contributing back to the environment by returning the water you pulled from the air. It's also good for hurling 1/2 a gallon at the neighbor's house window when they're sitting there with the boom box and blasting horrible music way too loud. You're not really wasting it.

spa31rky (author)Madrias3572010-07-07

I am not sure washing a CAR with such water is a very good idea. That water will contain contaminants that will "fog" the clear coat of the paint. Being a former Auto Detail-er myself I was very careful as to what water was used on any vehicle to prevent damage to the clear coat, or what used to be called PolyGlycoat. I used Teflon as a finishing product that would repel water and any contaminants and keep the clear coat like new.

Madrias357 (author)spa31rky2010-07-07

Considering the car I drive has peeling clearcoat, I figured I'd pass on my mention of what one can use free water for. I drive an old 88 Ford Taurus. I don't mind the clearcoat peeling.

spa31rky (author)Madrias3572010-07-07


treesneedtobehugged (author)2009-09-12

On the discovery show The Colony and you can see the video online from the website that they made a ozone machine that cleaned there water which came from the Los Angles river!

jwaterfallguy (author)2009-07-31

Really cool, creative way to harvest water. I had no idea that Tuscon actually required ac by law! That's intense! Check out our rainwater harvesting community: water harvest online. We would love to have you!

dripwater (author)2009-06-03

Check out the This might be of interest and assistance.

skincage (author)dripwater2009-06-03

Thanks very much! I'd discontinued the rig above until I had time to think about how to do it better. Now that someone has, I can contemplate a from-scratch version.

The Dark Ninja (author)2009-04-19

Ever thought about taking some of your water to a treatment plant of some sort to have them test it for drinkability? And you could also build a solar purifier to filter out the nasty stuff if you're really worried about it. Chances are you could even build it out of your existing setup with almost no major changes.

splatman (author)2009-04-13

I'm not sure how water sitting in a clear container in the sun be able to harbor bacteria. Non-bio contaminants, maybe. Google SODIS. As for the condensate pipe, finding a way to keep it completely full of water, so no air gets inside, may be able to keep it from getting funky. Try that by putting a U-bend at the end of the pipe that ends upward, followed by upside-down U-bend (or just a spout) to carry the water to the terminus w/o wetting the outside of the pipe. Sort of like a siphon. Use clear tubing for the U-bends. One possible way of sanitizing the con-pipe, is to run H2O2 thru it. Give it a Splat!

bladework (author)2008-09-30

have you thought about a solar panel(small one from craft proj.) to run your pump? why pay for the elect.

skincage (author)bladework2008-10-01

Yeah, I've thought of that. Harbor Freight has a solar fountain pump that I could use. After reading about all the ways this water can kill anything it touches, though, I'm wondering if it's worth the bother at all.

vger13 (author)2008-09-12

think i am beating a dead horse but...other than Legionnaires disease the water is just plain nasty,i wouldnt use it for anything i have been in hvac for going on 30 years and if you could see what comes out of a line when blown out you wouldnt even want it draining in your yard BEWARE of condensate

netbuddy (author)vger132008-09-27

Theirs all sorts of nasty bugs in condensate water. This has come from hot moist air that is ideal for transmitting disease and when that moist warm air is cooled... it concentrates what was air borne into a liquid. Very grim, anyone who works with fridges, freezer units in places like supermarkets... then they will tell you of the true horror of the fridge. These devices keep stuff cool but they also are a major bio hazard.

handydave937 (author)2008-09-07

Good Idea man, Here is another water saving tip, when I change my dogs water I use the stale water in the bowl to water all my house plants so no water goes down the drain.

skincage (author)handydave9372008-09-07

Mine drink it so fast I might never get the chance but it's a good idea. Thank you.

brettddglas (author)2008-09-04

If the condensate is coming from an A/C unit, this water is coming from the air just like when you sit a cold can or bottle out on a hot day the condensate drips off it. It is as pure as the air it came from so... but we use it all the time to water plants etc... with no problems. If it is a swamp cooler, there should be no concensate. water drips on a pad and when the water is low it adds more water with a float valve. There is no condensate line.

skincage (author)brettddglas2008-09-04

I actually kinda swiped this idea from one of my old neighbors. She had her cooler line in a bed of aloe plants and they were thriving. So far the aloe planter I set up is doing fine, and I'll keep an eye on it. I think the worry is that the water is condensing on metal which may be contributing poisons to it, and also that it's flowing through oldish pvc pipes which may be breeding bacteria. I think if I keep the line clean it should be ok.

uknative (author)2008-08-31

The water coming out of the condensate line from your ac unit has a very low PH, this is not safe to drink. It could also have some affect on your plants over a period of time. If you do use this water on your plants, you may want to test the soil every few weeks and use a balancing agent.

skincage (author)uknative2008-09-01

I did not know about that, thanks for the heads-up. At this point I think I will update my instructable to declare it a non-successful experiment, but I may use some of the components in other water systems with safer content.

chuckr44 (author)2008-08-28

I use my AC water to water my garden. I collect it in a 5g bucket. If my AC runs for 8 hours in a row I'll collect about 3 gallons of water, and that's for a small 800 sq ft house.

username (author)2008-08-24

Just an FYI You should be able to purchase a condensate pump for under $100. I just bought one to use during a renovation (had to move condensate line). Purchased from Baker Distributing along with 100' 3/8" tubing for ~$50 2 wks ago. Up to 17' of vertical lift. Try your local A/C parts distributors or commercial supply houses.

skincage (author)username2008-08-27

I'll take a look, thanks for the heads up.

Rishnai (author)2008-08-23

I also don't trust that pipe. You could boil and distill your water eaily enough and make it potable. Seeing as you're in Arizona, a solar still sounds particularly easy and promising. Boil first to ensure that any bacterial nasties are dead.

skincage (author)Rishnai2008-08-27

I will look into solar stills, as it's something I should probably know how to do anyway. Thanks.

iceni (author)2008-08-26

You may want to look into the link between Legionnaires disease and air conditioning.

skincage (author)iceni2008-08-27

I have looked into it a bit, and at this point I have no desire to use this water for drinking or watering edible plants.

thoxbui (author)2008-08-27

Would a solar powered UV light (with, you know, the UV LEDs) kill the little nasties? You can pickup a 51 LEDs flashlight from ebay for about 10 bucks.

skincage (author)thoxbui2008-08-27

That might work, at least on a small scale. Thanks for the suggestion.

dirtdoc (author)2008-08-27

Yes the water is technically distilled but the surface on which the water condenses is a nice bacteria farm and contains heavy metal contaminants such as lead, copper, aluminium, cadmium etc. The contact time of the water is such that the contaminants can be dissolved into or adsorbed onto the water molecules. Water analysis for metals and bacteria would cost about $300 dollars per sample from a commercial lab. Your county or state water well laboratory can probably do it cheaper. I would stick to watering only noncontact vegetation. Also a float switch (apprx. $20 at Lowes) can be plugged into any fountain pump with a standard wall plug. I put a bucket under my unit [hee, hee, I got to say Unit;)]with a fountain pump and float switch to provide water to several new planted trees in my yard 2 years ago.

skincage (author)dirtdoc2008-08-27

I think I will probably go with tree watering as my ultimate use for this stuff. Thanks for turning me on to the idea of a float switch.

echoclerk (author)2008-08-27

this just seems absurd. how much water do you thinka toilet wastes each day? and 100F is only 37C which although rather warm, really isn't that bad. I've lived in Sydney Australia for years without AC. its just not necessary. try turning it off instead?

skincage (author)echoclerk2008-08-27

You're entitled to your opinion, and I won't start a debate about whether Arizona or Australia is more hostile because you'll win that easily. I do have plans to use other means (shade, window treatments, etc) to decrease the need for A/C. Believe me though, there are parts of the year it's just necessary to retain civility. In the meantime, I just wanted to figure out a way to keep from wasting that water.

frollard (author)2008-08-24

I only read a few of the comments - but a note; the water coming out of a compressor-AC system is literally distilled water, 100% pure water. ---the only impurities would be those floating around in the air (dust, smoke etc) that get trapped in the water, hence why it is condensate. The only problem (as noted by a few people) is the fact that its not biologically sound, because mold is happy to grow in a sporadically used water pipe, open to the air. Great uses for watering plants, not so good for drinking. and to another person who suggests RO (reverse osmosis) water, it throws away 10x as much water as it produces as a final product.

Calorie (author)frollard2008-08-24

The effiecency of RO depends on the quality of the unit, and the difference between the quality of water in versus water out. RO Plants that make drinking water out of sea water use incredible amounts of energy and discharge a great deal of waster water. They can only purify a certain amount of water for practical reasons. The first is the energy cost. The second is that the salinity of the discharge has to be accounted for in environmental impact. A home RO is a good deal, especially when it is one that is not an entire house unit. Keep in mind all of the transport costs (petrol, time, etc) to haul and "purify" city water and then sell it to you (in plastic jugs, etc.) The environmental impact of an RO unit is a great compromise. On the other hand, you could just drink out of the tap. Most people cannot tell the difference. The US has the safest drinking supply in the world. Bottoms up!

rimar2000 (author)2008-08-24

Great instructable, congratulations. I have utilized that distilled water for the car: motor cooling system, battery and wiper. I suppose that to water the plants it is a lot better than the tap water.

skincage (author)rimar20002008-08-24

I hadn't thought of using it in the car. Great idea. There are plenty of uses for water beyond plants and drinking, which I've eliminated until I get a filtration system. This is why I love Instructables, all kinds of people bringing new ideas to enhance each other's work.

yoshhash (author)2008-08-23

Nice instructable. Dead simple, but clearly not obvious to most. My landlord was blaming me for leaks in the rooftop patio (by walking on it) but I shut him up last week by showing him a videotape of how much standing water was being created by the air conditioners. Imagine how much we collectively waste in North America (Europeans are not as a/c crazy as us), and all the water damage we cause by not capturing it.

skincage (author)yoshhash2008-08-23

It hurts my head trying to imagine that volume.

About This Instructable




Bio: i'm a noisician, information addict, and all around weirdo, and i'm gradually becoming proud of it.
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