Using water from dehumidifier in fish tanks

[Patrick]

Any thoughts? I have an abundance of humidity and 2 dehumidifiers and just noticed when I tested the ph came out at about a 6.5. As opposed to the tap here of almost a 9.2. I figured there shouldn't be anything bad for the fish or plants but wanted to ask you for your opinions. This would be a much easier way of gaining makeup water than off gassing and then lowering ph.

Thanks for your thoughts.

Tim

[Hank Paloci]

I would be concerned about any heavy metals that leech through the dehumidifier into the water. Can get the water tested cheaply? How old are the units? Do you know that there isn't any lead or other bad stuff in the piping of the dehumidifiers?

Otherwise, I like the idea.

[Ben Stallings]

Hi, Patrick.  I've been using my dehumidifier water (pH around 6.2) on occasions when I need to lower pH.  It seems to last longer than the other acids I have easily available.  My dehu is new enough that I don't think heavy metals are a concern, but I also am not raising food in my system.  If you have a way to test for that, I agree with Hank that it would be prudent.

[Paul Smith]

Hi Friends,

The water that comes from your dehumidifier is nothing but condensed water.  The way a dehumidifier system is designed is to cool the air by a refrigeration cycle; the cooler air molicules are condensed or closer together and can't hold as much moisture. This is the same thing that happens when you see water on the outside of a class of ice-water.  The air just around the glass is cooled, causing the moisture in the air to collect on the side of the class.  Eventually, enough water will collect on the glass so it will run off.  The same thing happens in a dehumidifier.  The only heavy metals that will be in the condensate is the amount disolved in the moisture in the air.

I guess you could say, 'OK, so I am condensing the moisture out of the air that might have heavy metals disolved in it."

Yes, we do have acid rain, so if you live in an area of heavy air polution, you might have some heavy metals disolved in the air.  Just think, You breathe that same air and your fish and plants are having to also filter that air.

I have used water collected from an air conditioner drain for batterys and steam irons for years.  If you need a source of condensed water, you have a great source.

Paul

[Ben Stallings]

Hi, Paul.  I can't speak for Hank, but my concern was about the metal the dehumidifier's evaporator coil is made of, which the water is condensing on and running down on its way to the tank.  Since it is not intended for potable water, it is not required to meet the standards of typical plumbing for lead content in the solder, or for that matter in the coil itself.  Having not taken a dehumidifier apart, I'm not sure what metal the coil is made of and whether it is soldered, but I imagine it might be.  :)

[Jim Enterline]

I have been doing this from the air conditioner condensation drain water. The only thing that I have noticed is that I have had to add iron and potassium. Evidently it must remove some of the trace elements in the process. But have had no major issues with the fish, however the change out has only been about a .2 lower in ph each time with about 15% change out.

[Hank Paloci]

I would think that the "waste" water coming from a dehumidifier is going to be unbuffered water, of similar quality to distilled. The danger in my mind is that a dehumidifier isn't engineered to create water for human consumption (and, by extension, for AP), and as such the coils in which the water cools may be made of or contain metals (Pb, Hg, who knows) that we don't want in our system. This is less likely to be true with a new unit. I'll bet you can look up the specs and figure it out.

There may also be molds or fungi that accumulate in the coils when it isn't running -- think about how an AC unit in your house or car smells when you fire it after not using it for awhle.

All in all I would think that you could rule these out and use the water.

[Jon Parr]

Because the condensate is acidic, and the condenser is likely aluminum fins over copper tube, then you will likely have metals in the condensate, and copper is no bueno. Better safe than sorry, and use the water for non-fish functions. IMO.

[Hydro Clif]

I work for a company that makes dehumidifiers.  Over the years we have had this question come up many times.  Some folks want to use the water to make drinking water, others want to use the water for gardens, and others for fish tanks.  Recently I gathered water from 3 dehumidifiers and sent it to a labratory for extensive testing.  The oldest unit was over 10 years old and had all original parts, the newest unit was brand new.  Long story short, the water that we collected passed a well water test and was more than acceptable to be consumed by humans.  The water was superior to tap water.  In regard to heavy metals, most dehumidifiers use copper pipes, just like the water pipes that many homes utilize.  These pipes are brazed together, not soldered, just like the water pipes in many homes.  I can't talk for other brands specifically, but I can say that it is most likely that all dehumidifier create safe potable water. 

 

Test results

Nitrate 0-.19 ppm

Aluminum 0-11.8 ppb* (*parts per billiion)

Copper 0-74.9 ppb*

Zinc 0-0 ppb*

 

All three units were under the limit for acceptable drinking levels of Bromate, Chlorite, Chloramine, Chlorine and

Chlorine Dioxide.

The published article will have more details and should come out in the March, April or May edition of Maximum Yield magazine. 

 

[Ben Stallings]

Thank you, Hydro Clif!  That's very helpful.

[Glenn]

First, it doesn't make economical sense to run a dehumidifier JUST for the water that drips from the coils that was deposited there by the condensing vapor in the air.

Second, the water will not be purified. The particulates in the air will also land on the coils and be accumulated into your collection system. And in many places with brand new coils, the tds total dissolved solids of the drip water measures 30 or more ppm, and more used coils the drip gets dirtier. The drip from central air conditioners is similar. And even rain water from roofs is often measured with 100 ppm or higher tds.

This being said. if a dehumidifier is in continuous use for any other reason, the drip water can safely be captured and purified prior to its inclusion into our AP system. Rremember that anything we put in and don't take out, accumulates and eventually will cause harm or make small or large volume replacements required.

I do capture rain water and the drip from my a/c. But I filter it using non system root plants and purify it with ozone prior to using it as makeup or topping off water in my AP system. It does save some water and money but it's not a huge saving.

There are several fairly low priced meters and test kits for tds. Here's a link to one source.

 http://www.waterfiltersonline.com/water-tests.asp

The hot coils on a dehumidifier can also be converted to stainless steel and submersed in AP water to capture warmth.

Here's a link to a video showing how one inventive aquaponist does it.

 http://www.youtube.com/watch?v=IN5LlZ5VsWE

[Aquamaple]

Glenn,

I'm so glad you shared that. I was just about to search the forum (and still plan) for people with experience using and keeping rainwater, when this topic happened to catch my interest. My well water tests about PH 8.4 so I am looking for a way to create system water that is safe with a lower PH. I plan on being on this property for a long time, and plan on increasing my system capacity substantially, so I need to get a water solution figured out.

    Is there already a discussion going on about your rainwater collection? I'm curious to hear how you are doing it. I was thinking about collecting rainwater from the roof of the greenhouse. I would even build a "food grade" stand-alone dedicated collection device, if it would work well. I have a serious water problem.

Thanks!

Mark
 
Glenn said:

...And even rain water from roofs is often measured with 100 ppm or higher tds... I do capture rain water and the drip from my a/c. But I filter it using non system root plants and purify it with ozone prior to using it as makeup or topping off water in my AP system...

There are several fairly low priced meters and test kits for tds. Here's a link to one source.

 http://www.waterfiltersonline.com/water-tests.asp

[Alex Veidel]

Glenn, is that water example based on a tar based roof? Just curious if you knew...

I usually run my rainwater through a charcoal filter before using it, since my roof is tar based. Aquamaple, what material is your greenhouse roof?

 
Glenn said:

...And even rain water from roofs is often measured with 100 ppm or higher tds... I do capture rain water and the drip from my a/c. But I filter it using non system root plants and purify it with ozone prior to using it as makeup or topping off water in my AP system...

There are several fairly low priced meters and test kits for tds. Here's a link to one source.

 http://www.waterfiltersonline.com/water-tests.asp