Graywater Harvesting

freewomynFebruary 28, 2009

I am curious if anyone recycles the run off water from their evaporative cooler to water their plants. I was told last week in a gardening class that this is OK, and then this week I was told that the water is too salty and will kill your plants. Any advice from experienced graywater/rainwater harvesters would be much appreciated.


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It may depend on where you live and what your source of water is, but I did this in Tempe for many years without any negative consequences.

Give it a try. If your plants start showing signs of excessive salt, then you could stop.

Good luck.

    Bookmark   March 2, 2009 at 2:28PM
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There are two things to consider when using water from an evaporative cooler.

1. If you use the water that flows over the pads and then exits the cooler you will probably not harm your plants, however, this could be very inefficient depending on how much extra water you are dealing with. Coolers typically use between 90 and 200 gallons of water per day.

2. If the water is recycled through your cooler with a pump and flows over the the pads more than once, accumulated salts in the water will be harmful to your plants. Some coolers have a float in a basin in the bottom that allows fresh water to fill the reservoir. Then the water is cycled to the top of the cooler pads over and over. The water that accumulates can be almost like brine and very salty.

Here's a link to more information.

Here is a link that might be useful: Evaporative Cooler Water Use

    Bookmark   March 2, 2009 at 6:59PM
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aikanae(z9b AZ)

I've done this for years without any problems. The first cooler was one that might have been 30 years old. Now I've got a MasterCool with clean machine that dumbs every 8 hours. I see no difference. I just hooked up a soaker hose and forget it.

If I was watering plants that like acid soils - gardenias - I can imagine a problem.

    Bookmark   March 3, 2009 at 8:10AM
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azgypsie(z9 Tucson)

We have a gizmo on our cooler (I can't think of what it is called) that dumps the water out every 6 hours and puts fresh water in. We use that water to give all of our plants a drink. After only 6 hours, I don't think the water has time to get too salty and we have the added benefit of never having that old fish tank smell in the house. Said "gizmo" can be found at Ace Hardware in their cooler parts section.

    Bookmark   March 9, 2009 at 11:13AM
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