420 Magazine Background

Can I use water from the dehumidifier?

Smokin Moose

Fallen Cannabis Warrior
Dehumidifier water can be used for watering container plants and in hydroponic reservoirs. It reads 10ppm or less on a TDS meter. Water that sits stagnant can harbor mold and bacteria however, so you may want to oxygenate the water before using it. Oxygen levels are easily increased by shaking it in a jug or adding hydrogen peroxide. This will kill the harmful bacteria and your plants will benefit from the extra oxygen. The dehumidifier water is very soft water, since it has been recondensed from vapor which lost its mineral content when it evaporated. Many people use it to soften their tap water.

WARNING: Dehumidiers often employ copper tubing. If the resulting water is 10ppm its possibly 10ppm of copper. Adding this to your reservoir every time will start concentrating the metals-- since plants only need under 1ppm of copper, using this water could accumulate to the 100ppm toxicity level.


New Member
The water that comes out of the dehumidifier is pure, distilled water. There are going to be trace elements (copper and aluminum) from the coils and fins, but those should be minimal.

If you research this issue, you will see a lot of hysterical posts regarding bacteria and mold spores in the water. Since you are basically running ALL the air in your grow room through the fins, anything airborne is bound to end up in the water.

But anything airborne is also bound to end up settling on your plants and grow media anyway, especially if you are using a drip system rather than say, a grow mat covered in plastic.

3M sells a flexible allergen filter: the Filtrete 'hammock filter'. Filtrete is the trademark for most of their filters, including rigid furnace filters; you do not want any of those. The hammock filter is a flexible sheet and removes almost all dust and about 100 percent of mold spores (mold spores are huge compared to many allergen particles). Tape a sheet of that over your dehumidifier intake. The air filter that comes with the dehumidifier is crap and will let everything but the biggest dust particles through.

The reason growers get bacterial buildup in their dehumidifier water is that they rely on the crap filter in the unit and don't clean the fins or the tank regularly. Leave a bucket of RO water uncovered in your grow room for a couple of weeks and you will end up with bacteria and mold-laden RO water.

Use the 3M filter and clean the fins and tank weekly and you should be fine using the dehumidifier water. Skip either of those steps and you will end up adding a bacteria/mold soup to your reservoirs.


New Member
i have opposite problem need to raise humidity , humidifier putside on floor are fine, correct? i go through wter 2-3 times daily dump hot/warm water down drain/sink
Top Bottom