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.

Therefore, the type of water we use significantly affects 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 a poor-quality water.

  • Signs of Water Problems in Plants
Signs of Water Problems in 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.

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

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

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

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 the cannabis.

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

  • Soft Water
Soft Water
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Opposite to the 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.

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

Finding the correct balance of hardness in water is the 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 mountain, 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
Reverse Osmosis and Ionic Filters
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While we can soften water using softeners, this is potentially harmful to the plants. In this process, sodium is the essential ingredient that removes the 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.

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
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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.

  • Correcting Water Problems

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

  • High Sodium Concentration
High Sodium Concentration
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As mentioned, high sodium can be damaging to the cannabis crop. But an extremely dry soil with salts can be fatal. 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 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 assists the roots in absorption. In addition, when the sun is too hot, the chlorine may react by causing nutrient burn.

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 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 a pH and TDS testers.

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 a 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.


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  1. By James

    ,12 Jul 2014
    Hello Robert – I wanted to alert you to a new filter I have designed specifically for growing cannabis. It will remove chloramines entirely and it will remove or reduce fluoride, depending in part on local water chemistry. In most […]Read More
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    1. By Cheis

      ,04 Aug 2016
      Is rain water good
      Was this comment helpful to you?
  2. By Jeremiah

    ,29 Mar 2015
    I’m using lake water in SW Colorado for our indoor and outdoor plants. The ppm is around 1100 before I add my organic nutrients. It goes up to over 2000 after I add them. Is it necessary to get a […]Read More
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  3. By The?

    ,20 Jul 2015
    where i live in the uk the tap water is f$%#in’ shite. hard as diamond, mmmm, well u get my drift….? i reckon. it also has well over 300 ppm of other solids, salts, minerals. gazillions of it….not great. gonna […]Read More
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  4. By latewood

    ,23 Jul 2015
    Hello The?, I would not apply hydrochloric acid to my plant solution. I would stick with phosphoric acid, or go buy a battery refill kit at the auto store. It is pure diluted sulfuric acid , I use this all […]Read More
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  5. By Symptom Checker – Identify Marijuana Plant Problems

    ,24 Jul 2015
    […] Hard or soft water […]
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  6. By When And How To Water Marijuana In Soil

    ,03 Aug 2015
    […] When it comes out of the tap, your water could have an EC that ranges from 0.2 to 0.8, or even higher. The real issue here is that even when you take an accurate measurement, there is no way […]Read More
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  7. By kcaven

    ,10 Sep 2015
    Can bottled water be used? Distilled? Regular? thanks!
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  8. By latewood

    ,12 Sep 2015
    Distilled water is perfect for growing. The downside is that you have to constantly buy and tote water every week. This can become tedious. Invest in an 4-5 stage Reverse-Osmosis unit. This will provide you with years of pure water; […]Read More
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  9. By chris

    ,03 Oct 2015
    I have a female clone that wa given to me it was just a few inches tall but had already started to flower so i took it home and put it under 24 hours 400 watts hps and it turned […]Read More
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    1. By Steve Dutch

      ,11 Mar 2016
      Hi Sir , When plants have less fingers on there leafes it are 2 things or mayby 3. 1/ not enough light or not the right collor light 2/ the strain growht as 1 finger leafes ,i thought some Dutch […]Read More
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      1. By Jennifer ILGM

        ,14 Mar 2016
        Hi Steve, Im not sure what you mean, but can you email pictures with more detailed information to support at [email protected], so we can take a look at it.
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    2. By ken

      ,16 Nov 2017
      plants will grow strange after forcing veg state you may even see round leaves. perfectly normal.
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  10. By latewood

    ,05 Oct 2015
    chris, Really do not have an answer for you. you re-vegged a small plant in flower. I would probably cone it. I suggest you join our Support forum and post a picture in order for us to see what you […]Read More
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  11. By kman

    ,10 Oct 2015
    i have moved from hard water area in england to soft area in scotland im in soil and perlite and others in coca am i going to have problems or will soil buffer my nutes or do i go organic […]Read More
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  12. By Problems That Cause Marijuana Plants To Stress

    ,18 Nov 2015
    […] If you find out that your water contains undesirable minerals or elements, your best bet is to use filters to purify it. Try to avoid water softeners, as these may fix one problem, but might add other elements you […]Read More
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  13. By Lucky

    ,31 Dec 2015
    Soft water with chemicals(which are acidic)lead to acid enviroment bcs soft water doesnt have enough alcali salts to compensate acid from fertiliser…If u have distiled water(without any salts) and mixed with ferts,you had to much acid enviroment(distiled water get same […]Read More
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  14. By Ak47luver

    ,12 Jun 2016
    Hey Mabey you can help I had female super skunk indoors under 24,hours cfls I put it outside on May 1st it started flowering within 2weeks and is still in flowering on June 10 it’s like 15 + hours a […]Read More
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  15. By latewood.ILGM

    ,08 Aug 2016
    Ak47luver, Sorry to have missed this. We have been having a chronological issue with our blog for a couple months. You always want to feed bloom nutes in flower. Hope everything turned out alright. For more available knowledge; Join our […]Read More
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  16. By latewood.ILGM

    ,08 Aug 2016
    Cheis, Rain water is great, however, you still need to test the PH and make sure you are collecting this rain water in a potable water reservoir, ro at least food grade. 55 gallon soap drums are acceptable vessels for […]Read More
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  17. By sen

    ,26 Oct 2016
    hi,can u please help me with a report here,,um struggling to find related reports for my literature topic is effects of hard water(not saline) on growth and yield of tomatoes
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  18. By Mark

    ,28 Jul 2017
    Great article as always
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  19. By 1BigFella

    ,07 Sep 2017
    One thing about Colorado River water is you never need to add Epsom Salts: It has lots of Calcium and Magnesium already. Another important thing to know is that most home water softeners get rid of calcium and magnesium by […]Read More
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  20. By Adamant

    ,08 Sep 2017
    Ok so soil sample from 4/10/ ph 8.2 Nitrate nitrogen med/high12ppm ammonium nitrogen low 12ppm phosphorus high100ppm Potassium very high 250ppm Calcium high 1600 Magnesium high125ppm Any suggestions? Things are nice but if theres more i could do for the […]Read More
    Was this comment helpful to you?
    1. By latewood_ILGM

      ,26 Sep 2017
      Adamant, You sure do not want to add that much phosphate. Looks like you need to amend the Nitrogen most of all. However you are missing several other essential minerals. Seems like pretty good soil to start out with. I […]Read More
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  21. By Camille A.W. O’Hara

    ,21 Sep 2017
    I am using rock wool and rocks as my growth medium. I started out with purified water but the salt cause my last batch to be stunted and they never produced buds. So I started over, not realizing then that […]Read More
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    1. By latewood_ILGM

      ,26 Sep 2017
      Camille A.W. O’Hara, Salt on the rockwool is just because the top is dry and you see residual salt. I suggest you join our forum and post your questions. There are some small qualifications you must meet before posting […]Read More
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  22. By VASILEIOS vasileiadis

    ,06 Oct 2017
    i already downloaded your bible which is perfect as far as i read.Thanks a lot dear sir for so gentle gesture.Live long stay strong and high
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  23. By James G

    ,28 Mar 2018
    I use dehumidifier water, pH is 6.3 constant and hardness is .53 ppm appr. My concern is, I added soluble food to water the plants, the pH didn’t change but the hardness went to .13ppm I can’t figure out what […]Read More
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    1. By latewood_ILGM

      ,18 Apr 2018
      James, I don’t know what to tell you. If you ppm went down to almost nothing after you added nutrients; I would say your meter is fried. I honestly do not know Go here: and we can help you […]Read More
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  24. By Tricia Fisk

    ,30 Aug 2018
    I have a reverse osmosis system but it seems like i get them perfect then use the ros water they start having problems i have hard water so i got the ros because everyone said hard water is not good […]Read More
    Was this comment helpful to you?

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