Reverse osmosis (RO) is an advanced water filtration method that uses a special membrane to remove up to 99% of dissolved salts, heavy metals, chlorine, organic pollutants, nitrates, and other substances from water. Under high pressure, water is forced through a semi-permeable membrane; water molecules pass through, while most contaminants are left behind on the other side.
Why Use Reverse Osmosis in Cannabis Cultivation?
In cannabis growing—especially hydroponics—reverse osmosis is valued mainly for the ability to control water quality completely. RO filtration produces water almost free of minerals (TDS at 0–10 ppm), allowing the grower to precisely add nutrients without risk from invisible contaminants in tap water that could disrupt mineral balance or pH in the reservoir.
If you use tap water, its hardness (high mineral concentration) can reach even several hundred ppm. Such water “competes” with fertilizers, makes it harder for plants to absorb nutrients, and can cause pH swings or toxicity of certain ions in the roots. In hydroponics, where the plant entirely depends on the nutrient solution, this is a real risk for serious growth problems.
When Should You Use RO?
Whenever local water has a high TDS/EC value or contains a lot of calcium, magnesium, or other minerals.
In hydroponics—it’s practically standard, especially for DWC, NFT, or aeroponic systems.
When growing with high precision (e.g., growers using Athena or Advanced Nutrients feeding schedules).
If your water comes from a well, old plumbing, or areas with high pollution.
How to Use RO Water?
RO water is pure but almost devoid of minerals. Before watering or filling your reservoir, you should “condition” it by adding calcium (Ca) and magnesium (Mg), adjusting the pH, and mixing in proper nutrients. You dose everything yourself, gaining full control over the solution’s composition. This precision minimizes the risk of plant stress, nutrient burn, or micronutrient deficiencies.
In Summary
Reverse osmosis in cannabis cultivation—especially hydroponics—represents a solution for growers who want complete control and no risk over their growing conditions. With RO, you know exactly what your plants receive, eliminating any unwanted interactions caused by tap water. It’s an investment not just in pure water, but in healthy plants, fast growth, and maximum genetic potential.
