Fresh water is often regarded as an infinitely available resource in the eyes of the Earth’s inhabitants. People also underestimate its role as an essential input to the basic fundamentals of survival.

For an ever-increasing population with an increasing demand for resources such as water, the consumption of these resources is occurring at a faster rate than production, and will eventually lead to long-term shortages. Shifting mentalities from treating water as a disposable resource to a finite, renewable resource is an important change we should all be considering.

Finding the cleanest source of input water possible is a goal that all growers share. There are three stages involved in implementing an effective water management program in the growroom: acquisition, treatment and disposal. We start off with potential sources of acquisition.

Available Water Sources on Planet Earth

Only 3% of the world’s available water is fresh water. The remaining 97% of the water on the planet is sea water. Desalination is the process of converting salt water into fresh water, typically through reverse osmosis or distillation. Both practices require expensive equipment and are impractical on a large scale.

The two main sources of fresh water are surface water and groundwater, which are both supplied primarily through precipitation. Surface water is found in lakes, rivers and other man-made reservoirs, and groundwater is water that has accumulated underground as a result of rain seeping into the soil. Depending on where you live, your water may be coming from either of these sources and may require additional inspections and treatment before being safe to use in your growing system.

Water Treatment Options

There are several different ways to treat your water. Various filtration methods are available to treat contaminated water, waste water or hard water, depending on your source. Water with a high content of dissolved solids should also be treated prior to circulation to effectively follow common feed charts in hydroponics, as these were designed assuming input water starts at 0 ppm.

Mechanical Filtration

Mechanical filtration occurs when water filters are used to treat source water, or recirculating water. The most popular and effective mechanical filtration system used in hydroponics is the reverse osmosis filter, as many of them are able to catch up to 98% of contaminants. Compared to the functionality of conventional filters, RO filters are able to catch particles as small as 0.001 microns, including impurities on the ionic scale. Be careful when choosing an RO filter system, however, as many of the parts may be made from poor-quality materials and don’t function the way they are intended.

Chemical Filtration

Chemical filtration is a process by which chemicals that break down contaminants are added to the source water. Use caution when implementing chemicals in your system, as some may be harmful to you or your plants. A good example of a safe and effective chemical commonly used in hydroponics as a means of chemical filtration is hypochlorous acid (HOCl). HOCl has powerful oxidative properties that dissolves pollutants including mineral deposits that form harmful scale and biofilm. HOCl removes potentially toxic contaminants from the water that could otherwise lead to additional issues, such as creating harboring sites for diseases, plugging up your plumbing and trapping organic matter. Using a small dose of hypochlorous acid regularly is one of the best preventative measures available that can be taken to promote healthy water and, subsequently, healthy plants.


Biofiltration is commonly used in organic hydroponics and aquaponics. It occurs when a grow media acts as a biofilter by hosting a site where beneficial micro-organisms can multiply. The micro-organisms then work to biologically break down the pollutants in your water. Various grow mediums can be used as biofilters, such as coco coir, bioballs, expanded clay and grow rocks. Providing an adequate biofilter surface area for the beneficial micro-organisms to thrive is crucial for their existence. Because biofilters are prone to clogging and other issues, growers should use multiple filtration techniques.

Water Disposal

The final stage of water management is disposal. Where does your water go when you are done using it? If you are flushing your water down a drain, then most likely a large volume of it will ultimately be pumped back out to its original source, such as surface water. Prior to that, some waste water will be pumped to a sewage treatment plant to undergo strict processes enforced by agencies such as the EPA.

There are several different steps to transform waste water that can contain high concentrations of potentially toxic contaminants into water with standards that classify its quality as acceptable. Some of these steps include the use of filters and chemicals that trap and break down the contaminants, similar to the procedures growers use to purify their input water prior to irrigation.

Unfortunately, a large volume of waste water is pumped directly back into watersheds without any treatment whatsoever. This carries a number of health risks to humans and the environment. With water being in short supply in many areas of the world, certain industries like the agricultural industry are competing for treated waste water.

This happens because other industries such as municipal water districts tend to get priority over farmers to serve their customers. Because cultivating plants requires large volumes of water, farmers are forced to settle for untreated waste water. Growers are encouraged to treat the water themselves prior to cultivation to ensure sterile growing conditions.

As gardeners, we can do our part in improving the water management cycle primarily by reducing waste. Recirculating water for longer periods of time through various filtration techniques will reduce the frequency of disposal. Monitoring your input water for impurities, along with treating your water regularly, is critical to preventing water-borne pathogens that can be harmful to both you and your plants.