How to Get the Best Water for Marijuana Plants

Along with light and nutrients, water is vital in the nourishment of marijuana plants. Aside from assisting in photosynthesis, it also keeps the plant’s internal temperature cool.

Most importantly, it carries all the nutrients in the soil to the roots so that it can consume what it needs. So, read more below to find out what the best water for marijuana plants is.

Therefore, the type of water we use significantly affects the nutrition of the plants. As such, we must ensure to hydrate the crop using only the most suitable kind. This is especially valuable when we want to produce huge buds that are rich in THC.

In general, many types of water are available for the growers to use. This includes tap water, rainwater, purified, and distilled. When it comes to availability, all of them are accessible and cheap. But which one gives the most desirable outcome in growing marijuana?

In this article, we will explore the different kinds of water and how they affect the plants. Also, we will learn how to balance and correct common water problems to make them optimal for the crop.

Choosing the best water for marijuana plants

As mentioned, the quality of water is crucial for the healthy growth of plants. Hence, this section will discuss its various types and their specific traits. This way, we will be aware of their properties and make informed decisions on which type to use. But first, we must know the signs that the plants are suffering from poor-quality water.

Signs of water problems in plants

water problems in weed plants
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Overall, the plants will look weak and wilted. Also, they may exhibit signs of various nutrient deficiencies. In worst cases, they will stop growing and we can say goodbye to our dream of harvesting some buds.

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    Types of water for weed plants: Soft and hard water

    Basically, there are two main types: soft and hard water. Interestingly, their names have nothing to do with how they look or feel.

    Types of water for weed plants
    Types of water for weed plants

    Rather, we base the classification on the concentration of minerals that they contain. The unit of measurement for this is 1 mg/l of contaminant = 1 ppm.

    Many beginner growers struggle to know when the best time to water their marijuana plants. We’ve put together this Cannabis Watering guide to help!

    Hard water

    We define water that has a high content of dissolved minerals as hard. Primarily, hard water contains high calcium and magnesium content.

    To measure its hardness, we look at how many milligrams of calcium salts there are in a liter of water. So, 200-400 mg/L is the range for hard water while 400-550 mg/L is for very hard.

    What does hard water do to cannabis
    Hard water

    In general, tap water floats along the range of 170-390 mg/L. While it is not dangerous to humans, consuming this type of water can be harmful to cannabis.

    Oftentimes, calcium deposits in the roots may block the absorption of other nutrients. If not corrected, this usually results in nutrient deficiencies. Thus, we must soften hard water to render it more suitable for the crop.

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    Soft water

    Opposite to hard water, soft water contains very little minerals to none at all. According to the water hardness scale, less than 150 mg/L is very soft, while 150-200 mg/L is simply soft.

    soft water on cannabis
    Soft water

    A good example of soft water is rain, but it eventually becomes filled with various minerals as soon as it hits the ground and runs in the soil. In any case, it is one of the best types of water for plants. Other great examples are purified, ionized, and distilled water.

    How to balance water for your weed plants

    Finding the correct balance of hardness in water is a challenge for many growers. For cannabis plants, the perfect water is soft, within the range of 100-150 ppm or mg/L.

    Unfortunately, tap water in the mountains, by the sea, or in big cities usually goes beyond this range. So, how do we make hard water soft? The following methods will show us how.

    Reverse osmosis and ionic filters

    While we can soften water using softeners, this is potentially harmful to the plants. In this process, sodium is an essential ingredient that removes calcium and magnesium. However, sodium salts can build up in the soil and attach to the roots over time.

    Worse, the high salt content fools the plant into thinking that it has ingested enough water. In effect, the plant will die from thirst. Thus, using special water systems such as reverse osmosis or ionic filters is preferable.

    Reverse osmosis and ionic settings for weed
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    Other reliable systems are carbon filtration and distillation. Essentially, they purify hard water by safely removing all the minerals, salts, and other impurities. Hence, we get pure water that allows the plants to completely absorb nutrients in the soil. Also, it preserves the health of the roots.


    Cal-Mag for weed plants
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    Oftentimes, the methods mentioned above make the water too soft. Since 100-150 ppm is the ideal range that produces healthy cannabis, we must adjust the hardness level by adding Cal-Mag. So, using a TDS meter, test the number of dissolved solids in the water and adjust it to the right value.

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      Correcting water problems for weed plants

      Unfortunately, growers must deal with several problems regarding water quality. Often, the issue stems from a high concentration of certain minerals present in tap water. Luckily, there are easy ways to fix them.

      High sodium concentration

      As mentioned, high sodium can be damaging to the cannabis crop. But an extremely dry soil with salts can be fatal.

      High Sodium Concentration for weed plants
      High sodium concentration – Image powered by

      To alleviate this problem, feed the plants filtered water to help dilute the high mineral concentration. For a more lasting solution, improve the soil drainage and switch to using well-balanced water.

      High sulfur in the water

      High Sulfur in the Water
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      Water that smells like sulfur is highly acidic and can easily weaken the plants. To be sure, use a pH meter to confirm the suspicion, then add lime to the soil to make it less acidic.

      Chlorinated water

      Chlorinated Water
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      In most cases, tap water contains certain amounts of chlorine. But when the concentration is too high, this can kill a lot of beneficial bacteria that assist the roots in absorption. In addition, when the sun is too hot, the chlorine may react by causing nutrient burn.

      Also read Nutrient burn in marijuana plants

      To fix this problem, use activated carbon filters or chemicals that remove chlorine. For some growers, letting the water sit overnight usually does the trick. But the best solution would be to invest in a reverse osmosis system to get the best type of water all the time.

      The right water produces happy weed plants

      To sum up, good-quality water is vital to get healthy plants that produce high yields of potent buds. Fortunately, even if we only have access to tap water, there are ways to adjust it to become more suitable for the crop. For best results, invest in special water systems and mineral measuring equipment such as pH and TDS testers.

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      Now that we know how to achieve the best type of water for marijuana plants we can be confident in feeding it. If we start with good seeds and provide the basic needs, using well-balanced water will further help them thrive. So, practice this skill consistently and enjoy a successful harvest by the end of the growing season.

      Is distilled water good for weed plants?

      Yes. Distilled water is an example of soft water, which is great for weed plants.

      What’s the best water filter for growing weed?

      Reverse osmosis or ionic filters are some of the best water filters for growing weed. However, you can also use carbon filtration and distillation to purify hard water.

      What is the best water for growing plants?

      Soft water is the best water for growing your weed plants. Some examples of soft water are rain, distilled, purified, and ionized water.

      Avatar for Robert Bergman

      Robert Bergman

      Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations. His passion for growing led him to develop his own Gold Leaf strain. Now, Robert is dedicated to sharing his knowledge with the world.... [Read full bio]


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