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Condensate Water for Irrigation: Worth the Risk?

With the explosion of opportunities for indoor and greenhouse hydroponic facilities, the focus on efficiency becomes increasingly important. Sustainability is the feature that will ensure that your indoor or greenhouse grow stays viable and profitable for years to come, which is why it’s important to have progressive practices in place as early as possible. Water is a key resource that can be dramatically conserved and optimized when it’s properly managed, so developing a plan is critical for the overall success of your grow.

As regulation for commercial cultivation operations and competition increases, growers are becoming more sophisticated by sharpening their horticultural skills and refining the technology in their facilities. Grow room design is becoming more data and science driven. Many indoor cultivators are opting for sealed rooms and closed loop systems with every input stringently monitored and criticized including all water resources.

Water sources for both indoor and greenhouse grows are typically provided either by the city or from well water, and the quality of either type of water can vary dramatically. Most cases require a water treatment plan. In the majority of large scale commercial hydroponic facilities, dehumidification and air conditioning are an absolute necessity. Both of these systems have a constant flow of condensate water which is normally lost down the drain as waste water. In an effort to conserve water, many growers consider using this water for agriculture. This makes a lot of sense as the water, in theory, is distilled from the air and should be relatively clean. In order to determine the true viability of this water source, it’s important to analyze its quality and the HVAC system that is producing it.

Not all climate control equipment is built with the same materials, which means that the condensate water quality can vary depending on the individual system. Time is also a factor, as the internal parts age and collect dirt and bacteria and affect the water quality in different ways.

Suspended Solids

Dust and other suspended solids that collect inside air handlers, dehumidifiers, and condensate lines accumulates in condensate water, becoming a major issue. This debris will vary with the age and make of the climate control system, and how clean or dirty the indoor grow area is, but it is necessary to be aware of these contaminants and take measures to reduce them.

Comparison of a new and used sediment filter from a condensate water filter
Comparison of a new and used sediment filter from a condensate water filter

Chemical Quality

Taking a look at the quality of the water in terms of minerals is a bit complicated. Upon testing water with a traditional TDS meter, you will hopefully notice that the discharge from the unit reads very low in TDS (ppm). This makes sense, as this is distilled water vapor from the air. However, just because the TDS meter reads 0 ppm does not mean that there are no minerals or harmful substances in the water. The internal coils in air handlers, dehumidifiers and other mechanisms contain heavy metals that will leach into the condensate water. Some of these specific metals are considered harmful in very low quantities. The EPA has limits for certain contaminants. Lead, for example, has a toxicity rate of 0.015 ppm and would be undetectable by a TDS meter yet still poses a risk. Copper has a maximum allowable level of 1.0 ppm and zinc is 5.0 ppm. These levels may seem low but they can be harmful nonetheless. Although heavy metals like this would likely not have immediate effects on most crops, it can bio-accumulate in the mass of the plant material or in the growing media which would certainly affect overall quality. Those wanting to grow fully organic and as pure a crop as possible, these heavy metals should be totally absent in the irrigation water.

pH Levels

Another consideration is the pH of the condensate water. Typically, the overall mineral content is very low and therefore the water tends to absorb atmospheric CO2 making the water very acidic. The pH level can test below 5.0 points. This means that the water is corrosive and will absorb metals and other contaminants depending on what it comes in contact with in the facility. Adding a buffer and re-mineralizing the water will resolve the pH issue.

Biological Contaminants

Biosecurity in high tech grows is also another major issue when it comes to using condensate water. As any experienced grower knows, harmful pathogens can become a huge issue and take lots of effort to track down and ultimately control. Precautions should be taken to ensure that pathogens are not introduced into condensate water destined for reuse by plants. The internal coils and other components of air conditioning and dehumidifier systems are ideal environments to harbor numerous species of bacteria. Observing untreated water in condensate storage tanks, you will see slime and other species take hold and grow. Not all bacteria is harmful, but this type of environment acts as a breeding ground for harmful species. Legionella is an airborne bacteria responsible for outbreaks among humans and has been traced to condensate water. Treating this water involves the use of ultraviolet sterilization or chlorination.

Dirty condensate line
Dirty condensate line

Using Condensate Runoff from A/C and Dehumidifier Units for Agriculture

Due to the potentially harmful qualities of condensate water as outlined above, the cost of treating this water is minimal compared to the potential damage caused by using raw condensate water. To protect the longevity and safety of your indoor or greenhouse grow operation, it makes sense to treat the water for each of these problems in order to prevent a much larger problem later. There are turnkey solutions available to the modern grower that can address all of the issues associated with untreated condensate water. These solutions offer a relatively economical insurance policy to protect your valuable investment.

HydroLogic has a four stage filtration solution for condensate purification called the ARCS.