Tuesday, August 3, 2010

Why didn't we...

This project was originally published on Windborne In Puget Sound in May, 2010.

I don't know why we didn't. You would think that we would have long ago.

Living aboard and dealing with the problems of humidity, especially in the winter when the boat is sealed up should have pointed us at this solution sooner.

In a dock gathering discussion last week, we realized that most of the other boats were keeping dehumidifiers running in the winter.

But my memories were of the huge clanking monster of a dehumidifier that my parents ran in the basement of our childhood home. It was a heavy, file cabinet-sized unit that needed its own circuit - it drew 15 amps. Not exactly appropriate for a boat.

But now we have the world's products at our fingertips - I did a quick Internet search and found this one - it draws only 1.6 amps, is small enough to live in the aft head, and yet is capable of pulling 25 pints of water/day out of the atmosphere inside the boat. It even has provision for a continuous drain (which I haven't set up yet), that would go right into the shower sump it is sitting above. Oh yeah... and that is distilled water it is producing too - ideal for the batteries. Finally, condensing water produces heat, so it functions as a small space heater too (you can almost think of it as a tiny heat pump).

One of the dangers of living with problems is that they cease to be viewed as problems after living with them long enough. If it hadn't been for that casual dock conversation, we'd still be living with the humidity.


  1. Another cool product that I need to look into :)

    hmm... ok I got cross eyed on that one... I was thinking of using it on the hook with the inverter.. At 12 volts it is pulling 15 amps. sigh... I guess that is better than the ac system at about 80 amps :)

    something to note is that the water produced by most dehumidifiers is not considered safe to drink unless you filter it first. It is considered good for use in batteries. here is a brief blurb that talks about the safety aspects..


    General dehumidifier water is considered a rather clean kind of greywater: not suitable for drinking, but acceptable for watering plants, though not garden vegetables.[2][4] The concerns are:[4]

    * the water may contain trace metal from the solder, most significantly lead (which is quite damaging), but also copper, aluminum, and zinc;
    * various pathogens accumulate in the water, particularly due to its stagnancy, including fungal spores; unlike in distilled water, the water is not boiled, which would kill pathogens (including bacteria);
    * as with distilled water, minerals are largely absent, hence it is somewhat flat tasting.

    The trace metal poses a danger if used on edible plants, as they can accumulate; however, the water is otherwise usable for irrigation.

    One can make food-grade dehumidifiers (avoiding toxic metal and keeping the collection tank clean), which are called atmospheric water generators.

  2. good link addressing the above

  3. audeojude: Because of all the air that passes thru the dehumidifier, the condensing moisture acts like a kind of stripper, trapping all the dust, bacteria and virus particles that are floating in the air. No way would I drink that stuff.

    Before you get too excited about the trace metals content of the dehumidifier water, you should do a reality check and compare it to the trace metals content of your favorite drinking water. I suspect that you'll find that the dehumidifier water is orders of magnitude better in that respect.

    But so far, the best use I have found for the prodigious amounts of water produced by the dehumidifier is to dump it in the head as flush water, leaving it to steep in the lines. Distilled water is a pretty good solvent (ask me how long a cross-plant distilled water line lasted sometime).


  4. Instead of using an inverter for 12v operation, I'm considering something like the 'Sunpentown Mini Dehumidifier SD-350' from Walmart.. It's a third of the price at $49, 12v operation (thermoelectric), hold 2 liters of water, it's smaller (13"h 8"W 5"D), "whisper quiet", and attractive .. and the reviews are good. However, it doesn't state the amp draw in the specifications, and I've not actually bought one yet, so I can't say it's the ticket.. Nevertheless, worth consideration due to it's 12v capability

    1. Before you commit to that unit, you need to consider its capacity - not how much water the reservoir can hold, but how much water it removes from the air each day. From the ones I've seen, those small thermoelectric units are are not that effective.

      If you do get one of these, please report back here how it works out for you!


  5. After more research, I've completely abandoned the consideration. Not only due to the fact any peltier unit lacks any apparent ability of doing an effective job, but also due to the amount of energy it eats up while trying it's best to do what it ultimately cant do.
    It's just another candidate for "save a dime, loose a dollar.
    I'll take your advice of getting something like the NewAir AD-250 this summer.


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