Water Choices

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: we lack soil when producing our crop. This provides us with many advantages (more direct uptake of nutrients, arguably less bugs, clearer visibility to root zone), but one of the main drawbacks of using soil-less systems is mistakes tend to be much more 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 very regular system that is hard to perturb. Often, over-fertilizing is self-limiting in soil; excess nutrients will just persist in the soil (note: extreme over-fertilization will result in “over salting” which can be herbicidal).

Soil-less media users tend to have a much more difficult time hiding their mistakes. To be clear, when I say “soil-less”, 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 “soil-less.” 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 (taken from epa.gov), well water is coming directly from the groundwater source. The main issue with well water is the 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 (arsenic, cadmium, antimony, chromium, lead, among others)
  • chloride (kills beneficial bacteria)
  • sodium (stunts plant growth, can accumulate in sump)
  • industrial chemical runoff (plasticizers, volatile organic compounds)                   

Overall, we strongly recommend not using well water.

Option 2: Tap Water

For the personal/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 not as bad as well water because the groundwater is filtered at the water treatment facility (and tap water is very cheap!), but it certainly has its drawbacks:

  • 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. De-ionized water (or 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.

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. From a grower’s standpoint, reverse osmosis means we take “concentrated water” (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! 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 all 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:

  1. RO/DI Water

  2. Tap Water 

  3. 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!

Closing Thoughts

Overall, you have many choices when considering your water supply – depending on which you choose, Elite Nutrients can ensure your plants receive the proper nutrition.


Who is Dr. NPK? With a PhD in Chemistry from UC Irvine, Dr. NPK was instrumental in developing the Elite Nutrient line.  Learn more about him here.