Wasting clean water (and money) isn’t something most people like to do. So why do some growers throw money away by sending their dehumidifier condensate water to the sewer?
Simply put: They don’t think it’s clean. After talking to growers who dispose of condensate water, it’s clear that the reason for flushing it away hinges on a misplaced sense of caution that stems from seeing mold and fungus growing in and around the drain pans and hoses of old, window-mounted air conditioners. Beyond that, growers often express concerns related to copper tubing and soldered connections.
Too often, those discussions stop short before addressing plumbing concepts or short-term condensate storage that are critical to understanding how to safely reuse water.
A Quest dehumidifier is seen at a cannabis growing facility Thursday, Nov. 9, 2017 in Portland, Maine. Photo courtesy of Quest Dehumidifiers.
Fear of Heavy Metals
At Quest, we have repeatedly used certified, third-party testing labs to test dehumidifier condensate water for metals and organics. The test results have consistently indicated condensate water is safe to use. These tests are easy to replicate, and we recommend you do so with your own system.
The U.S. Environmental Protection Agency (EPA) defines safe contaminant levels in drinking water through the Safe Drinking Water Act of 1974 (individual states can establish their own standards if they are at least as strict as the EPA’s). The tests we’ve run meet these standards, but we still do not recommend drinking the water.
Additionally, all copper tubing connections are brazed not soldered, a critical manufacturing process because lead is not used in brazing.
Reclaiming Water
The actual plumbing you’ll need is fairly basic and shouldn’t be a problem for any commercial plumber. The details will depend on the type of irrigation system you use. In general, the concept is to pump or drain the condensate water into a short-term holding reservoir. The reservoir should be sealed tight with a lid that has a filtered vent, to allow the water level to rise and fall without developing pressure or a vacuum in the tank.
From there it depends on whether you inject your nutrients at line pressure or mix them in another holding reservoir. If your system does all the feeding from line pressure, treat your condensate tank as if you are pumping out of a well — use a pump, pressure tank and a backflow preventer if your other incoming source is municipal water.
If you mix nutrients in an open reservoir and allow gravity to do the rest, pump out of the short-term tank into your mix tank and add nutrients as you normally do.
Best Practices
To discourage possible mold growth, thoroughly dry any dehumidifiers that will be out of operation for more than a few days. If a dehumidifier has been sitting idle, run it for three days before you reclaim condensate water.
The resultant water will be within acceptable limits if the dehumidifier is in good working order and has proper air filtration — though for commercial growers, there may be laws or local regulations that require condensate water to be tested for heavy metals, nitrates and bacteria.
Many dehumidifiers produce condensate water that can be used as-is, as long as you keep the air filter in place and change it as the instruction manual explains. Dust, bacteria and other pollutants may get into condensate water if the dehumidifier’s filter is absent or not maintained properly.
The Takeaway
Don’t waste a ready, renewable and “free” water supply for your plants, especially if your water supply is costly or your area is dealing with drought conditions. Condensate water from your dehumidifier is always available. Best of all, it’s free, clean and safe — as long as you follow best practices.
Mike Steffes is a research-and-development scientist with Quest Dehumidifiers. He has worked with the cannabis industry for nearly seven years to build industry-specific products.