The Importance Of Water Purity in Cannabis Grow

Growers know a lot about their plants but don’t have the same care with their water. Remember, water is not just water.
23 September 2020
7 min read
The Importance Of Water Purity in Cannabis Grow

  • 1. Why is water important?
  • 2. What are the total dissolved solids (tds)?
  • 2. a. Where do the solids come from?
  • 3. Why measure the tds level of water?
  • 4. What is hard water?
  • 5. What is soft water?
  • 6. How to remove or reduce tds?
  • 6. a. Reverse osmosis
  • 6. b. Distilled water
  • 6. c. Deionization
  • 7. Extra tips for purifying water
  • 8. In conclusion

Water is not just water, depending on the source it can contain different minerals, metals, and other impurities that can end up affecting how your plant grows.

1. Why is water important?

As you may know, water is the most abundant compound and one of the most important substances on Earth, all living things need water to survive, without water there would be no life on Earth. 


The importance of water purity: why is it important?

Water is the most important compound for all living things one Earth.

Just like it’s vital to use, humans, it is also vital to all plants, including cannabis plants.

Water makes up for around 85-95% of a plant's weight, not only are they made of water but they also use water more than anything else in their vital functions.

Nutrient distribution

There are different types of nutrients you can use, synthetic or organic, synthetic nutrients will feed the roots directly and organic nutrients that make the minerals available in the soil.

In both cases, when you water your plants with a nutrient solution, the roots absorb it and transport it into the plant’s cell which is then used in combination with the other processes described above to produce sugars that are then used to grow and develop the stems, leaves, flowers, and seeds.


The importance of water purity: nutrient distribution

How organic and synthetic nutrients work.

Now, these processes will be performed just fine with any kind of water but depending on the water source it may contain a lot of dissolved solids that can affect how well these processes work.


Transpiration is the process of water evaporation from leaves and stems, this happens because water is necessary to plants but only a small amount is used for growth and essential processes, around 97% is used in transpiration.


The importance of water purity: transpiration

Transpiration is used by plants to help maintain the ideal temperature.

By evaporating the water, vapor is released in the atmosphere through the stomata, cooling the space around your plants, this helps keep an appropriate internal temperature and it’s essential because if the temperature is too high or too low, your plant will not be able to grow properly.


Photosynthesis is the process in which plants transform light energy into energy that can be used by them. 

Light energy is absorbed and used to convert carbons and the nutrients that are in the water into organic compounds like sugars that are used in plant development and growth.


2. What are the total dissolved solids (TDS)?

Dissolved solids refer to elements in water such as minerals, salts, metals, and anything dissolved in water other than water itself. 

Depending on the elements dissolved in water it will have a positive charge (cations) or a negative charge (anions) which can be measured by a TDS meter by measuring the electrical conductivity (EC) of water.


The importance of water purity: TDS meter

TDS meter measuring the dissolved solids in a solution.

Have in mind that the EC and TDS are not the same thing but both can be calculated by knowing the exact value of one of them, to transform EC to TDS you have to multiply the value by 1000 and divide by 2, to transform the other way just multiply by 2 and divide by 1000.

Also, remember that there’s no direct relation between pH and TDS but if the elements present in the water are acidic or alkaline, it can increase or decrease the pH level.

Where do the solids come from?

Dissolved solids can come from anything your water touches when traveling to your faucet, it may come from organic matter such as leaves, silt and from runoff water from farms or lawns that contain fertilizers and pesticides.


The importance of water purity: where do dissolved solids come from?

Dissolved solids come from anything water comes in contact before reaching their final destination.

They can also come from inorganic matter such as rocks or even air that contains calcium, nitrogen, iron, and phosphorus among others, water can also pick up dissolved solids from the pipes it travels through, usually, water picks up lead and copper which is the metals those pipes are made out of.

Now, some of these metals and minerals are used by cannabis plants but depending on the type of nutrients and quantity you’re using, your plants can have problems, that’s why it’s essential to measure the TDS from the source.

3. Why measure the TDS level of water?

The US Environmental Protection Agency advises that a maximum of 500mg/L of total dissolved solids, higher than that it can be harmful for human consumption, and this also applies to plants. 

The importance of water purity: TDS in water by source

Water source classification by TDS.

Depending on the elements present, watering your plants with water that has more than 1000mg/L can cause plants to have problems absorbing nutrients, and can cause stunted growth, and ultimately reduced yields.


Classification of Water

Fresh WaterTDS = less than 1,000 mg/LMineral-rich, safe for consumption.
Brackish WaterTDS =  1,000  to 10,000 mg/LSalt-rich can be consumed but not everyday.
Saline WaterTDS =  10,000  to 35,000 mg/LHigh amounts of salt, can cause an overload of sodium.
Hypersaline WaterTDS =  more than 35,000 mg/LExtremely high amounts of salt, should not be consumed.

Classification of water by TDS.

Elements like potassium, chloride, and sodium have minimal effects on humans and are not considered harmful. But elements like lead, nitrate, and cadmium are toxic so it’s essential you know what comes in your water, although it’s not common to find toxic elements in tap water.

4. What is hard water?

Hard water is water that contains a high amount of elements, such as calcium and magnesium, now these don’t present a threat to plants but can depend on the medium and nutrients you’re using.


The importance of water purity: hard water

Threats of hard water.

When watering with hard water, the elements can end up coating the roots and soil and actually repel water instead of absorbing it.

This way your plants can end up suffering from a nutrient build-up that can bring several problems such as overfeeding or nutrient lockout and even though you can fix it by flushing, it can be relatively hard.


5. What is soft water?

Soft water is water that also contains high amounts of impurities but instead of containing hard metals, it contains soft metals such as salt and sodium.


The importance of water purity: soft water

Whats is soft water.

Unlike hard water that coats the roots and causes water to be repelled, soft water makes your plants intake more water but your plants are being fooled by thinking they’re being fed, so instead of getting hydrated, they're actually dying of dehydration.

6. How to remove or reduce TDS?

There are several ways to completely remove or at least reduce the amount of TDS in your water by filtering it, and it’s done with special equipment, although this doesn’t mean they’re super expensive.

By purifying or filtering your water, you can effectively eliminate bacteria, parasites and viruses, organic and inorganic chemicals, heavy metals, gasses, and other contaminants.

Reverse osmosis

Reverse osmosis is a way to remove contaminants from water, it works by forcing it with pressure through a membrane that removes the contaminants and provides clean water.


The importance of water purity: reverse osmosis

How reverse osmosis works.

This system can have 3, 4, or 5 stages in which certain impurities are removed.

Each system contains the following type of filters:

  • Sediment filter 

Removes dust, dirt, and rust.

  • Carbon filter

Removes or reduces organic compounds like chlorine and other elements that can give water a bad taste or odor.

  • Semi-permeable membrane

Removes up to 98% of the remaining dissolved solid like minerals and metals.

Distilled water

Distilled water is a type of purification which is made by boiling water, after it boils, the vapor is then caught with a glass container and it quickly gets condensed and turned back into a liquid form.


The importance of water purity: distilled water

What is distilled water.

The impurities that were in the water do not boil at the same temperature so they are left behind in the original container, this doesn’t remove all of the dissolved solids but it’s a really effective way and has been used for a long, long time.


Deionization (aka demineralized water) is water that has had the impurities removed, this process works by using ion-exchange resins that bind to the impurities and filters them.

This type of purification produces high-purity water and is relatively quick but does not remove bacteria or viruses effectively. 


7.  Extra tips for purifying water

  • You can leave your water in a bucket at room temperature from 24hs up to a couple of days or have air stones in it to remove chlorine.
  • You can remove calcium and magnesium by boiling water but without the proper equipment, it’s impossible to know how effective it is.


The importance of water purity: tips

Tips for providing better water to your cannabis plants.

  • Have in mind that the quality of water can change over time so it’s essential you measure it or request an analysis every couple of months.
  • Even though our plants use some of the elements found in water, it’s essential you know the amount in it. The more impurities it contains, the less “good” nutrients your plant will absorb.

8. In conclusion

Even though it might seem that it’s just water, water is the most essential compound for all living things on Earth, and despite growers not realizing this when they first start cultivating, water is super important in all the processes your cannabis plants need to perform in order to grow healthy and strong so it’s super important to know exactly what you’re watering your plants with.

Obviously, you can water with whatever you want but by providing better quality water, you will see a big difference in the end results.

If you filter or purify the water you use on your plants, please share with our fellow growers in the comment section below if you’ve seen big differences and if you found it worth it.

External References:

  1. Effect of different water quality parameters on acid requirement to lower water pH. -  Bhardwaj, Sushant & Bishnoi, Arvind & Singh, Amandeep & Kumar, Narender. (2018).
  2. The uptake of alkaloids by plants from the soil is determined by rhizosphere pH. - Hijazin, Tahani & Radwan, Alzahraa & Lewerenz, Laura & Abouzeid, Sara & Selmar, Dirk. (2020).
  3. Hardness and total dissolved solids. - Gray, N. (2018).  
  4. Improved Method for Measuring Total Dissolved Solids. - Gilmore, Kevin & Luong, Huan. (2016).
23 September 2020