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growing cannabis with tap water

Growing cannabis with tap water

There are contaminants in the water that could be affecting marijuana growth.

Killing The Microbial Growth

Then there’s the concern over what effects residual chlorine has on the microfauna in soil. While University of British Columbia soil scientist Sietan Chieng notes that there are so many variables of what’s affecting soil that it may be nearly impossible to tell what effects chlorine and chloramine have on the microorganisms in soil, others note that chlorine kills many microbes that are doing the work of releasing the nutrients in soil that plants depend on for healthy growth.

Avoid Chlorine Toxicity

What effects do those chemicals have on plants in general and marijuana specifically? Plants need some chloride, which is a micronutrient, to grow, but too much of it — what’s called “chlorine toxicity” — can build up in a plant and result in browning, yellowing, or scorched-looking leaves. It can even cause leaves to fall off the plant entirely, which, in the case of a budding cannabis, of course, sort of destroys the point of growing it at all. And according to the University of Maryland Extension’s College of Agriculture and Natural Resources, “chlorine toxicity can result from air pollution in the form of chlorine gas, or from excess chloride in the soil.” But guess how that chloride gets into soil? Yuppers, by way of water — through swimming pool runoff, irrigation, salts that are added to streets when it snows, and of course, tap water.

Growing cannabis with tap water

If you plan to build your own rainwater collection system, check with your local regulations first. Some jurisdictions have rules against collecting rainwater for many reasons. Make sure your rainwater collection container isn’t exposed to environmental debris or vulnerable to leaks.

Using your tap water may be just fine, but it depends on the water quality. Read further to learn more about the water quality at your location and whether you need to adjust it.

Hard water refers to water that contains high level of calcium and magnesium compared to soft water, which has had these harsh impurities removed and contains sodium. Because city tap water often comes from reservoirs and water sources with high levels of contaminants, chlorine and fluoride are added as a safety measure. Soft water has no harsh impurities and contains very small levels of beneficial minerals or none at all, so it’s healthier for drinking, bathing—and cannabis.

For example, say your tap water has a pH of 8.5. By following the soil amendment directions and providing the plants with the correct amount, water pH may reduce to the perfect 6.5 level. To ensure that this is the case, additional testing will reveal if the tap water is at the appropriate pH level. Make sure you test the water after mixing in the soil amendments.

Why Tap Water Smells Like Marijuana

Finally, electronic or digital pH testers are the most high-tech and costly option, but deliver accurate and easy-to-read results. Commercial growers may use these to get a better reading and for its convenience. Remember to recalibrate your pH meter frequently to ensure accurate readings.

Adjusting your water to make it as perfect as possible for your grow is a sound cultivation best practice. While you can certainly grow cannabis with mediocre water, it won’t thrive like it will with water at the correct softness, the proper pH, and free from chlorine.

Municipalities may treat water with chlorine and ammonia, which converts the chlorine to chloramines in a process called chloramination. The process is used to remove the phenols (plant material) present in water. Chlorine alone is effective at disinfecting, but bonds with the phenols to produce chlorophenols that can smell and taste bad.

Tap Water

You can also boil and cool your tap water to dechlorinate it. Cold water contains more gases than hot water. Boiling your tap water on the stove for about 20 minutes will degas, or evaporate, the chlorine. Boiling water can be time-intensive and impractical for large-scale cannabis growing. Before watering your marijuana plants, ensure the boiled tap water has cooled to room temperature.

Water pH test kits are readily available and easy to use. Cannabis does best with a pH reading between 6-7. A level of 6.5 is perfect—even lower for hydroponic grows. For hydroponic cultivation, a level between 5-6 is best, with 5.5 being ideal. Most likely, your water won’t be right on target. While you can likely grow cannabis with it, your plants won’t grow with the same vigor that they will with pH in the proper range.