As a chemist, one of my favorite jokes to hear (No, it’s not the “Oh, you’re a chemist? Can you make the Breaking Bad blue stuff? Har har har") is the one about people “banning” dihydrogen monoxide because it’s a chemical. In case you missed it, “dihydrogen monoxide” is water! The good ‘ole H2O. Can’t live with it, can’t live without it! Today’s post is about water and the choices we have as growers in deciding what water we would like to use to grow our crop.
Why Should I Care About the Water?
Hydroponic growers are a subset of farmers; the difference is that we lack soil when producing our crop. This provides us with many advantages (more direct uptake of nutrients, arguably fewer bugs, clearer visibility to root zone), but one of the main drawbacks when using soilless systems is that any mistakes made tend to be amplified. When I grow tomatoes in my backyard using soil, I have a vibrant ecosystem taking place in the soil that acts as a buffer of sorts: the soil maintains a dynamic, regular system that is hard to perturb. Often, over-fertilization is self-limiting in soil; excess nutrients will merely persist in the soil. Only extreme over-fertilization can be herbicidal due to toxicity.
Soilless media users tend to have a much more difficult time hiding their mistakes. To be clear, when I say “soilless”, I am ultimately referring to any media that does not add any nutritional content to the plant; thus, coco and other nutrient/water-absorbing media are considered “soilless.” If you over-feed or under-feed your plants, that protective soil buffer is essentially gone, and you risk killing all your plants. Because it is so important to monitor precisely what you are feeding your plants, you absolutely need to know what is in your water, regardless of the type that you choose. In my opinion, there are certainly advantages to some types of water compared to others.
Option 1: Well Water
Well water isn't the greatest option that you have. As you can see in the diagram below (taken from epa.gov), well water is coming directly from the groundwater source. The main issue with well water is that it contains a large number of inorganic and microbiological contaminants.
According to the USGS Water Science School, groundwater (and thus well water) can contain the following contaminants:
- Residual pesticides
- Toxic heavy metals, including arsenic, cadmium, antimony, chromium, lead, and more.
- Chloride which can kill beneficial bacteria
- Sodium which stunts plant growth and can accumulate in sump
- Industrial chemical runoff which includes plasticizers and volatile organic compounds
Overall, we strongly recommend not using well water.
Option 2: Tap Water
For the personal and recreational grower, sourcing appropriate water can be challenging. After all, why not use the hose and set up to use tap water? Tap water is very cheap, but it certainly has its drawbacks. Additionally tap water is not as bad as well water because it is groundwater that has been filtered at a water treatment facility. Here are some of the reasons you may not want to use tap water:
- You have zero control over what the municipalities provide you. Your water composition could change from week to week; this will throw off your EC values and nutrient elemental composition.
- Although typically devoid of microbiological contaminants, tap water will likely contain various water treatment residuals (chloramine, for example).
- Tap water is usually very “hard”. This additional sodium, calcium and magnesium can impact your hydro system, causing calcium overload (which leads to cloudy sumps) and nutrient lock out. Sodium is also very dangerous in high concentrations to your crop.
Despite the above drawbacks, tap water is still significantly better than well water.
Option 3: DI Water or RO Water
My favorite options for hydroponic growing are RO water or DI Water. Deionized water (shortened to DI water) is purified through a filtration system that performs cation and anion exchange to yield high purity water. In general, DI water contains less than 50 ppm contaminants. DI water is not distilled water; distilled water is usually purer but it is purified in a different manner (Distillation, who woulda thunk it?).
Reverse osmosis, as you can guess, is the opposite of osmosis. Osmosis is the flow of molecules of water to higher concentration from lower concentration. Reverse osmosis, therefore, is when water molecules flow away from higher concentrations, which is the opposite of its normal flow. From a grower’s standpoint, reverse osmosis means we take “concentrated water” (which has lots of contaminants) and remove the contaminants by pushing the water through a semi-permeable membrane. What results from this is super high purity water (and a pile of contaminants). This is clearly what we want as growers! The main drawback of this process, however, is that a good deal of water must be wasted when purifying. On average, an RO system “loses” about ¾ to ½ of all the water that goes through the RO system. However, technology is constantly improving RO systems, and water waste will continue to be minimized.
Nutrient Considerations when Using Pure Water
My final ranking for water sources is the following:
- RO/DI Water
- Tap Water
- Well Water (Recommended: last resort)
Fortunately, the Elite Nutrient line is fortified with stable minerals that resist the various issues found in water sources. Elite Base Nutrient A and B are perfectly pH balanced and can tolerate a wide range of tap and well water hardness. If you are using RO or DI water, consider supplementing your nutrient regiment with Elite CalMag, which supplies vital secondary nutrients such as Ca, Mg, and Fe to your water. The result is pure water that is devoid of dangerous elements that contains important secondary nutrients!
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About the Author
Dr. NPK has been in the chemical formulating business for over 9 years. With a Bachelors in chemistry from UCLA and a Ph.D. in chemistry from UC Irvine, he has always had a passion for chemical formulation. Over the past several years, his focus has narrowed towards the research and development of products that are optimized for cannabis. He assisted in the development of the Elite Nutrient line and takes great pride in the products he created and uses himself. He has made it his mission to cut through all the pseudoscience available on the web and to educate readers on the science behind growing top-shelf bud.