Replies

1. GBA Editor
   Martin Holladay | Nov 08, 2016 04:25am | #1

   Rob,
   It's hard to imagine that a residential air conditioner would harvest enough water to provide useful amounts of irrigation for plants or landscaping.

   A common size for a dehumidifier is a 70-pint model. That's the maximum rating of the unit, not the typical amount of condensate. We're talking less than 9 gallons per day.

   I'll bet that under average conditions, a residential air conditioner produces significantly less than 20 gallons per day of condensate. Is that a useful amount of irrigation water? You decide.

   An online article agrees with my guess, noting that a residential air conditioner produces between 5 gallons and 20 gallons of condensate per day.

   The BuildingGreen web site provides an online calculator (an Excel spreadsheet) that allows you to estimate daily condensate levels under different circumstances. Here is the link: Revised Air Conditioner Condensate Calculator Available on BuildingGreen.com.

2. 
   Dana1 | Nov 08, 2016 06:58am | #2

   20 gallons/day (or even 5) per AC unit is plenty for hand-irrigation or drip irrigation of landscaping on a 1/4 acre residential lot, but you'd be hard pressed to keep a 1/4 acre vegetable garden healthy on those amounts alone. Fortunately some water falls from the sky in quantity from time to time...

   Through this year's drought in Massachusetts one of the guys in my condo used buckets to collect condensate from his and his neighbors' AC to keep the landscaping at their condo green.

3. GBA Editor
   Martin Holladay | Nov 08, 2016 08:03am | #3

   Dana,
   You're probably right. I have a rural perspective -- thinking in terms of a large vegetable garden and a half-dozen fruit trees. Fifteen gallons a day wouldn't go far in a drought.

4. Expert Member
   Dana Dorsett | Nov 08, 2016 12:07pm | #4

   Yep, you're not exactly going to be able to irrigate your rice paddies or nut orchards this way.

   The amount of infrastructure necessary to capture, store, and re-use residential or (even commercial building) AC condensate would require a HUGE price for water water to be even remotely financially rational, not the $500/acre-foot agricultural users in CA have traditionally paid (though that roughly doubled at various points during the extended drought.) It may make financial sense if/when collecting & storing it is cheaper than disposal in sewer systems (or dry-wells, recharging the ground water) but I'd be surprised if there are many real-world cases like that.

   Singapore has an intense water reclamation and re-use policy, with a lot of public money spent on conservation, treatement and re-use, but I'm not aware of anybody doing AC condensate collection and re-use, even there.

   https://en.wikipedia.org/wiki/Water_supply_and_sanitation_in_Singapore

5. 
   rhallen645 | Nov 09, 2016 11:35pm | #5

   Based on the calculator for our hot & humid climate, 20 gallons/day is readily-available in the summer...however even if we generated that all year, at our current cost of water (~$12 per 1000 gallons), we're talking under $100 a year in value of water.

   However, we already have a rainwater cistern capturing water from our roof & a pump supplying water to our irrigation for the garden & landscape. Could we somehow connect the condensate drain line to the cistern?

6. GBA Editor
   Martin Holladay | Nov 10, 2016 04:38am | #6

   Robert,
   Q. "Could we somehow connect the condensate drain line to the cistern?"

   A. I don't see why not.