Water Quality

H2O:  To Filter or Not to Filter! 

Water may seem like the simplest component of any hydroponic nutrient regime and is quite commonly overlooked, for this reason.  Water is actually one of the most vital constituents as it is the delivery vehicle for every bit of nutritive enhancement you wish to bring to your plants.  If your water contains unwanted elements you may experience nutritive toxicity or deficiency symptoms, leading to crop failure or significantly reduced yields.  Since water is available to growers in a variety of forms, here is a brief description of the most commonly encountered: 

Tap/Municipal Water: 

Can I use tap water to grow?  Yes you can use tap water to grow, however, while convenient and generally clean given the infusion of chlorine, tap water is known to have many components that can be both beneficial and detrimental to many plants.  Remember, chlorine only attacks organics, not inorganics.  What is in tap water?  Calcium and magnesium are commonly found in tap water and have nutritive benefits for plants but the form of calcium can be an issue.  However, sodium, halogens (Br, Cl), haloacetic acids (HAA5), trihalomethanes (TTHMs), and even a plethora of viruses and protozoans are also known to be encountered when using tap water, including the abundance of inorganic and organic chemicals like benzene and nasty heavy metals like mercury, aluminum, lead, cadmium, arsenic, and more are also found in tap water. 

Well Water: 

Can I grow with well water?  Yes you can grow using well water, however, it will generally contain little to no chlorine, have a plethora of beneficial ions like Calcium and Magnesium and is also known to contain many microorganisms (many bad) and toxic compounds that can endanger human and plant health.  Volatile organic compounds (VOC’s), heavy metals, nitrates, and even radioactive molecules can also be encountered when using well water.  It is definitely preferable to filter well water to avoid these nasty issues. 

Rain Water: 

Can I use rainwater to grow?  While rainwater is another free or inexpensive source, contaminant content is an important facet to consider.  Generally, cationic (positively charged ions – magnesium, calcium, etc.) content is relatively lower than tap or well water, however rain water is also more acidic.  The largest problem with rain water use is the method in which it was obtained.  Metal roofing and containers, plastic components and fittings can all lead to dangerous heavy metals and other impurities making their way into the water.  Pathogens are also quite common when utilizing rainwater – E. coli, Giardia, Cryptosporidium, and Salmonella are all but a few of the many microorganisms that can live in rainwater.  Again, unless your rainwater capture method is clean and free from contaminants, it is strongly advisable to filter the water before use. 

How should I filter water? 

Since all of the previously mentioned water sources contain contaminants that could interfere with plant health, it is clear to see that filtration is needed in some capacity.  Depending on your original water source, your filtration demands may differ.  See below for a brief explanation of commonly encountered water filtration techniques: 

Ceramic - used primarily for sediment filtration. 

Carbon - removes VOC’s, lead, arsenic, chlorine, and many other contaminants. 

Mechanical Filtration - used for sediment filtration.  Not able to filter chemical contaminants. 

Ultraviolet - used for eradication of microorganisms, bacteria, and viruses but does not filter sediment or chemical contaminants. 

Ozone - used for eradication of microorganisms, bacteria, and viruses.  Not able to filter sediment or chemical contaminants. 

Deionization - utilizes ion-exchange resins to exchange hydrogen (H+) and hydroxide (OH-) ions for dissolved minerals, resulting in mineral-devoid water.  Primarily this process removes any negatively charged (anion) and positively charged (cation) ions.  Bacteria, viruses, microorganisms, and uncharged organic molecules are generally not able to be separated from water through this process, however. 

Ion Exchange - much like deionization, ion exchange utilizes specialty resins that exchange desirable ions for non-desirable ions.   Water softening techniques use this technology - calcium and magnesium are exchanged for sodium.  This process does not remove bacteria, viruses, microorganisms, or uncharged organic molecules. 

Distillation - exploiting the differences in physical properties between water and many contaminants, distillation involves boiling water to vapor.  This vapor is then captured, cooled and condensed, while the majority of contaminants are left behind.  This method is effective for the removal of bacteria, viruses, microorganisms, and minerals.  Chlorine and various VOC’s are not removed from this process. 

Reverse Osmosis - a semipermeable membrane is employed to remove ions and large particles from H2O.  This particular form of filtration is able to remove bacteria and other microorganisms from water resulting in extremely clean water with near-zero EC/ppm. 

Is Your Water Hard Or Soft? 

What is the difference between hard and soft water?  When referring to the ionic content of water, the terms ‘hard’ and ‘soft’ are commonly used.  Calcium and magnesium are the ions of most particular interest and when levels of these 2 ions are high, the water is referred to as hard.  Conversely, when water is nearly devoid of calcium or magnesium content it is referred to as soft.  Water softening is employed when as excess of cations is experienced - this process displaces calcium and magnesium ions with sodium and/or bicarbonate ions.  Water that has been softened in this manner is rather detrimental to plants (and even some humans) due to high sodium levels and should be avoided.  Hard water, on the other hand, can be quite beneficial to plants (and humans) given that the cationic content is within appropriate levels and sanitizing agents (Cl) are allowed to dissipate. Growers using hard water will need to consider the cationic content of their water to compensate for the reduction in Cal-Mag and other minerals they will need to use. 

What is the best way to filter water?  For the purist, reverse osmosis is the most suitable option.  Starting with pure H2O, growers are able to know exactly what components are being fed to their plants.  Having complete control over the elemental components and their concentration eliminates many errors leading to nutrient deficiency and toxicity.  Also, the removal of heavy metals and some organic and inorganic chemicals is necessary when growing crops meant for human consumption. 

How much does a water test cost?  Regardless of the water source you choose, lab analysis should be performed to understand actual content.  While there are many laboratories EPA-certified to analyze drinking water that can analyze a wide panel of ions and contaminants for around $100, many at-home test kits have emerged in recent years - some for as low as $10 at local home improvement centers.  With technology this affordable, every serious grower should have their water source(s) analyzed for content.  With this last factor dialed in, you will be able to accurately and effectively provide nutritive enhancement to your plants to fulfill their true potential!  Start with clean water and nutrients and end up with a clean product!  The Dutch Master Commercial Edition range of nutrients and additives is guaranteed to have no detectable heavy metals, is filtered to 0.5 microns and has zero added hormones or PGR’s.  See the Dutch Master Nutrients Heavy Metals Analysis Reports on the Downloads page. 


  • Water can be obtained a variety of ways - most commonly tap/municipal, well, and rain.  Content varies greatly but all contain contaminants. 
  • Filtration is commonly used to clean water for use with plants - many types of filtration are available to the grower.  The particular type of filtration that will work best for your depends on the water source and what constituents are desired. 
  • Reverse osmosis is the best and cheapest option when looking for a clean water source with no pathogenic and ionic mineral content. 
  • Hard water contains a relatively high amount of cations such as calcium and magnesium.  Can be useful for plants, if ionic concentration is within appropriate levels but check first via analysis. 
  • Soft water usually contains an excess of sodium that is used to displace calcium and magnesium from the water source.  This water should be avoided if at all possible due to the excessive sodium content. 
  • Water tests are simple and affordable, with at-home tests kits available from as low as $10!