Why is Water Quality Important While Growing Cannabis?

Water is super important for every living thing on earth, and that includes your cannabis plants, too. Without water, your cannabis plant will not even sprout from the seed, let alone grow into a big aromatic Christmas tree that gives you gifts at the end of the harvest. 

In fact, water makes up 95% of your cannabis plant’s weight; not that your plant is made of water but it has more water than any other compound, and water is crucial for your cannabis plant’s health and yield. 

Learn everything you need to know about water quality in this article. 

Why Does Your Cannabis Plant Need Water?

Water serves many functions in the cannabis plant, right from cell division to photosynthesis, but discussing them all would take days. Instead, let’s sum up the most important functions water serves in your cannabis plant here. 

• Distribution of Nutrients and Energy 

When growing cannabis, you feed your plant via irrigation, and you also add many other nutritional supplements including organic or synthetic ones. Regardless of the type of nutrients you use, the roots absorb the nutrients and transport them to other parts of the plant. 

Within the plant, the nutrients are then used to produce sugars. These sugars, i.e., energy, are then diverted to various parts of the plant like the stem, leaves, branches, flowers, etc. This transportation of the nutrients, right from the roots to everywhere else within the plant, is carried out by water. 

• Transpiration 

Your cannabis plant uses a lot of water — in fact, it is quite a thirsty plant — but did you know that it only uses 3% of its water for most things and 97% for transpiration? Transpiration is the process where water evaporates from the leaves and stems, and it is a significantly crucial process for your plant’s survival. 

When your plant transpires, the water gets evaporated in the form of vapor from small pores on the leaves called the stomata. This cools the ambient space around your cannabis plant, helping the plant keep an ideal internal temperature. This process also helps the roots suck more nutrients from the soil. 

• Photosynthesis 

This is the process by which your cannabis plant generates energy. Here, it transforms light’s heat into energy, converting nutrients in the water to sugars. Water is important and without it, your cannabis plant will fail to produce energy even if you place it under the best light. 

Why is Water Quality Important for Cannabis Plants?

Water is important for cannabis, no doubt about it, but you can’t just use any water when growing cannabis. Some beginners don’t pay a lot of attention and overlook the quality of water. It is a crucial aspect when growing cannabis and a stepping stone to becoming an intermediate grower. 

Just because the water looks clean or is safe to drink does not mean it is good for your cannabis plant. As mentioned above, cannabis is over 90% water, so the quality of water you use can have a significant impact on your plant’s growth and health. 

When you use low-quality water, the natural processes of your plant, including photosynthesis and nutrient distribution, can be greatly impacted. In worse cases, dirty water can completely ruin your plant’s natural processes, which can affect your plant’s growth, health, and yield. 

For beginner growers, this is not much of a concern. Most gardeners and new growers use regular tap water and their plants grow just fine. But if you want to become a better grower and want to grow cannabis on a commercial level, water quality becomes important, and so does water treatment. 

The quality of water has an impact that goes beyond just providing the plants with hydration. When the water quality is poor, it can greatly hinder the growth and development of cannabis plants resulting in problems that can compromise the health and yield of the crop. Water, as you already know, plays a role in shaping the plant’s overall well-being and productivity.

When you use low-quality water, you’ll notice various problems. Often, the grower might try to find solutions but they are all in vain if the water is bad in the first place. 

For instance, if you’re using water that has too many minerals or is high or low in pH, the plant can suffer from stunted growth. Excessively acidic or alkaline pH can prevent the plants from absorbing nutrients. 

In addition, if the water contains too much chloramine and other heavy metals, they can be toxic and disrupt the growth of the plant. You’ll notice signs, like reduced plant height, limited branching, and a smaller plant size.

This is because untreated water can contain various impurities, minerals, and chemicals that your plant does not require. In fact, even if your plant does need certain nutrients, untreated water can contain an excess of them, leading to nutrient lockout or toxicity. 

For example, calcium and magnesium. These are two crucial micronutrients that your cannabis plant needs for good growth and yield. But if you give your plant too much calcium and magnesium, expect it to suffer from cal-mag toxicity soon enough. 

Additionally, some chemicals and impurities that are commonly found in water, including chlorine and bacteria, can also have terrible effects on your cannabis plant. These impurities can lead to diseases, and low growth, and even impact the overall yield and flavor profile. 

This is why you must use high-quality water and treat it if required. You can do this in various ways, including reverse osmosis, basic filtering, pH balance, etc., depending on the type of water you have at hand and what needs to be controlled. 

Using high-quality water, whether you are growing cannabis in soil or with hydroponics, is important and cannot be overstated. As you use high-quality water, you can get the most out of your cannabis cultivation. This brings you one step closer to growing a high-quality yield with minimal variations and good quantity. And you don’t have to worry about water creating any problems for your plant. 

Part 1: Total Dissolved Solids

Your water has many solids or salts dissolved in it, including various minerals, metals, and specific salts. Depending on the quantity or concentration of these dissolved solids in the water, you can have a positive or a negative charge, which is also known as cations or anions, and you can measure with a TDS meter. 

In most cases, you’ll be using an EC (Electrical Conductivity) meter, which measures electric conductivity; you can use a formula to convert EC to TDS. Remember, both EC and TDS are two different things, but can be calculated easily if you have one reading. 

For example, if you want to convert EC to TDS, you simply have to multiply the EC reading by 1000 and then divide by two. The other way around, multiply TDS with two and divide the answer by 1000. 

You must also remember that TDS is not related to pH, which you will learn more about later in the article. 

So, where do these dissolved solids come from? They can come from various sources that the water touches before it reaches your cannabis plant. It can come from organic sources like silt, runoff water, leaves, or other organic matter. 

Water also contains inorganic matter that can come from the air or rocks. These sources bring various compounds like nitrogen, iron, calcium, and phosphorus. Water can sometimes pick these compounds from the plumbing system, too. 

So, why is TDS important? So that you don’t give your cannabis plant more nutrients than it needs. For example, the US Environment Protection Agency (EPA) recommends a maximum of 500 mg/L of TDS for drinking water. Beyond this, the water can be harmful. The same applies to plants. 

Depending on the kind of dissolved solids the water has, anything over 1000 mg/L can be harmful to your cannabis plants. This can cause all kinds of nutrient-related problems for your plant, including nutrient toxicity, lockout, or burns. The eventual result can be stunted growth or reduced yields. 

Of course, you can do a thorough lab test of your water to know exactly which minerals are present in what quantities, but that’s often overkill for most growers. So, simply measuring the TDS levels should be enough. 

Part 2: Water pH — Acidity vs Alkalinity 

The second part of the equation is the pH of the water. The pH refers to the level of acidity or alkalinity in the water, and this is down to the amount of positive hydrogen atoms present in the water. 

The pH scale ranges from 0 to 14, with 7 being neutral, up to 7 being acidic, and over 7 being alkaline. 

Cannabis roots absorb nutrients from the growing medium, and each nutrient has a specific pH range where it can be absorbed best by the roots. You can’t fine-tune the pH to meet the ideal range of each nutrient, but you can narrow the pH level down to an average, so it can work for all nutrients to some level. 

Why is this important? If the pH is too high or low, the roots may fail to absorb some nutrients entirely. This can lead to uneven or inconsistent nutrient uptake or nutrient deficiencies. In some cases, the wrong pH can even lead to excess uptake of some nutrients. 

By ensuring the pH of the water is proper, you enable the roots to absorb all the nutrients found in the water. Here’s the thing — pH is different for different kinds of water. Some water sources are more alkaline whereas others are more acidic. So, even if the water is rich in all nutrients but is alkaline in nature, the roots may fail to absorb some or all nutrients. 

How to Check Water Quality? 

When you want to check the quality of the water, you’ll be checking the pH and TDS among a couple of other things. Remember, your water has traveled a long way to reach your home; sometimes, even crossing state or country borders. 

Also, water quality differs a lot. Your water quality may be entirely different from the water your friend drinks a few blocks away. So, you really need to check the water quality every time you switch your water source. 

So, what do you need to check before you start feeding water to your cannabis plant? Here are a few. 

• Check the pH of the Water

You need to always check the pH of the water before you feed it to your cannabis plant. You need to do this every time you switch water sources, add supplements or nutrients to the water, or change the growing medium. 

Checking pH is not only about water quality; this is one of the fundamentals you need to keep in mind when feeding your cannabis plant. Without the pH, you are growing cannabis in a dark room without a torch. 

To check the pH, you would need a pH meter or pen. There are various kinds available on the market, but you don’t need the most expensive one. A basic pH pen is more than enough; just make sure it is pH-calibrated before every use. 

Cannabis plants like a pH range between 5.5 to 6.5 in hydro and 6 to 7 when growing in a soil medium. It’s your responsibility to ensure the water you feed your plant has a pH level that falls between this. However, the ideal pH reading can differ based on your local climate, the nutrients you use, and the growing method at use. 

Generally, if you are growing cannabis in soil, you should stick to a pH of around 6 during the vegetative stage and increase it to 7 when your plant enters the flowering stage. For coco coir or hydroponic systems, the pH should be around 5.5 during the start of the vegetative stage and 5.8 as your plant grows bigger. You can then change the pH to 5.9 as your plant reaches bloom and 6.3 during the final weeks of flowering. 

Changing the pH of the Water

If the water you are using is not in the right pH range. Don’t sweat it. It happens more commonly than you’d think, and most times, it may not even be your fault. So, how do you change the pH? 

Start by calibrating the pH pen to remove one level of redundancy from the formula. Many growers forget this step and end up changing the pH from the right range to the wrong one without even realizing it. 

In most cases, you can calibrate the pH by testing RO water with a neutral pH, but follow the pH pen’s manufacturer’s recommendations for the best method. 

Speaking of pH meters, you should also learn to take care of it. It’s a delicate device that can give wrong readings if it’s not maintained well or is dirty. So, use maintenance liquid or pH calibration liquid in the sensor cover, store the pen upright, and be gentle while using it. 

Coming to changing the pH of the water, you need to take a few steps here. First, measure the pH of the water. If the pH is not right, you can either decrease or increase it using various methods. 

For most growers, the best method to use is pH up/down solutions. These are solutions that you add to the water to either increase or decrease the pH without affecting the nutrients present within. 

These pH up/down solutions are relatively cheap and readily available, and they are easy to use. Again, always follow the manufacturer’s recommendations to ensure you don’t overcorrect and throw the pH in the other direction. 

If you are preparing nutrient solutions, you can even use pH-perfect fertilizers. These fertilizers automatically tune the pH of the solution to the ideal levels that are required for your cannabis plant. 

As an added measure, you should also measure the pH of the runoff water that drains out of your plant’s container. Sometimes, the quality of water can be affected by the growing medium if there is a buildup of salts within. 

The runoff water should have a similar reading as the water; slight variations are okay, though. If the runoff water shows drastically different pH levels, you need to flush the growing medium with pH-neutral water to remove all the excess salt buildup. 

• Check the TDS of the Water 

Next, you need to check the TDS of the water. While you can get TDS meters for this task, you can also use simple EC meters that test the electric conductivity of the water. You can then use the formula mentioned above to convert EC readings to TDS readings. 

This meter will test the concentration of salts and minerals in the water. So, if the EC/TDS is too high, your water is concentrated with minerals and salts, which may not be safe for your cannabis plants. 

If the EC/TDS is too low, the water does not contain enough salts and minerals. Without supplemental nutrients, the water may not contain sufficient nutrients to sustain your cannabis plant. 

For most cannabis plants, you need water that has a TDS of under 640 PPM. Remember, if the TDS is over 200 PPM, your plant may show higher sensitivity to pH fluctuations, so the two tests go hand in hand. 

Changing TDS of the Water 

Like the wrong pH, sometimes, your water can even have wrong TDS levels. In most cases, you’ll need to reduce or remove the TDS in the water, which can be done by filtering the water. 

As an added benefit, filtering the water will also remove parasites, viruses, and bacteria from it, making the water safer for your cannabis plant to consume. 

One way of removing TDS from the water includes reverse osmosis, which uses forced pressure and a series of membranes to remove contaminants from water. This will ensure the water is clean and free of most contaminants, but you will have to add fertilizers to the water after this stage to make it beneficial for your cannabis plant. 

You can also use a carbon filter to reduce organic compounds in water like chlorine and other contaminants that may produce odor or bad taste. You can also use a sediment filter that removes rust, dust, and dirt from water. This is good for dirty water. 

Lastly, if you are sure you are going to add nutrients to the water to make a nutrient solution, you can even use distillation. This process completely eliminates any contaminants and minerals from water, leading to pure water. 

If nothing helps, you can always switch the water source. In many regions, regular tap water or well water is too rich in dissolved solids and may not be suitable for growing cannabis. In such a case, consider using rainwater or bottled water. 

• Check Water Hardness

As an added safety measure, you can also check the hardness or softness of the water. Contrary to popular belief, softened water isn’t clean water. Here’s how. 

Hard water contains elements like hard metals that can coat the roots and repel water, leading to nutrient build-up within the soil and nutrient deficiency in the plant. Sometimes, hard water can also cause nutrient burns in the plant due to excess hard metals. 

On the other hand, softened water also contains impurities but it contains soft metals like sodium or salt. Soft water can make your cannabis absorb more water but instead of getting hydrated, your plant may experience dehydration or nutrient deficiency since the water lacks hard metals. 

There are many ways to check the hardness or softness of water, but the best method is to use liquid detergent. Fill a bottle one-third way with water, add a few drops of dish soap, and shake the bottle. If the water turns cloudy with no fluffy bubbles, it is hard, and if it produces a lot of foam, it is soft.

• Get the Water Tested

If you are growing cannabis in large quantities, don’t mind spending some money, and are sure to use the same water source for a long duration, you should consider getting your water tested with a water test kit. 

You can purchase such a kit at your local gardening supply store, but they can be a bit pricy. This kit will give you a detailed analysis of the water and the kind of minerals and salts it contains. This is recommended for large cannabis farms or commercial setups. 

Water Sources for Cannabis Cultivation

• Rainwater 

Rainwater is generally considered the best water source for plants. First, it’s almost free and usually doesn’t contain any contaminants either. However, despite what popular opinion dictates, you must understand that it all depends from one region to another. If you live in locations that are polluted, then rainwater may not be that clean either. 

This is why it’s important to check the water quality, whether you’re using rain or tap water. Once you determine that the water is safe for plants, you can rest assured that you won’t have problems in the foreseeable future. 

Rainwater can be used to grow plants both in soil and hydroponics, as long as you test it. If the pH and TDS are within the acceptable ranges, you’re good to go. If not, make sure you adjust both parameters so your plants don’t suffer. 

• Spring water 

Spring water is another good option, but it can vary depending on the region it originates from. It comes from the ground and is good for humans as well, making it a great choice for plants. However, you need to make sure the pH is in the right range. Do not blindly use spring water as the pH can sometimes go above 6.5. You should also check the TDS as it could contain some minerals. While one brand could show a reading of 100ppm, another could be as high as 600! Thus, adjust the parameters and then feed it to your plants. 

You’ll also find some variations with added minerals, known as mineral water. Mineral water, as the name implies, is nothing but water with minerals. It could be carbonated too. Although you can grow cannabis with this, it’s simply impractical as it gets expensive. 

• Tap Water

Almost everyone around the globe can access tap water. Therefore, it’s the most inexpensive and practical way to grow any plant, including cannabis. Rather than spending money on bottled water, you just need to turn on your tap, collect it, and feed it to the plants. 

But wait…tap water is good, no doubt, but many municipalities treat tap water with chlorine or chloramine to protect your health by eliminating bacteria and pathogens.

Although these chemicals are necessary for human consumption, they can present challenges in cannabis cultivation. Specifically, chlorine and chloramine can potentially disrupt the balance of microorganisms in the soil, which can negatively impact the health and nutrient cycling process for plants.

While you can eliminate chlorine by simply letting the water sit for about 24 hours, chloramine will not evaporate easily. Another issue you’ll face is the unpredictability. While tap water from some regions can show a pH of about 7, others could be about 8, which is not good for cannabis. Your TDS numbers will be all over the place too. 

So, test the water and adjust as necessary. 

• Distilled Water

Distilled water is water that’s devoid of minerals, bacteria, and other contaminants. It has nothing, so it’s a good candidate to grow cannabis, but it’s not cheap like tap water. With an EC of 0, you can add the nutrients you want and tailor everything according to your plant’s requirements, but it’s not good for beginners who may not understand how to add nutrients from scratch. Most nutrient brands give you instructions to use tap water as it already contains some minerals, but you may get confused while working with distilled water as you have a blank page in front of you. 

If you decide to go with distilled water, make sure you check the pH and TDS after adding the nutrients. You should also wait for at least 30-45 minutes after mixing the nutrients to let them settle down so you get accurate readings. 

• RO Water

Reverse Osmosis water can also be used to grow cannabis. You just need to get an RO filter filter and install it in your home or purchase the water if you feel the filter is too expensive. Either way, if you plan to use RO water for a long time, it’s best to purchase the filter. 

RO water is as pure as it gets. Although it’s not the purest, like distilled water, you can still use it without issues to grow weed. Whether you’re growing in soil or hydro, you just need to adjust the pH as the pH is often around 7. 

• Well Water

Many people advocate for well water as it’s natural; however, it may not be the best source as it’s not as easily available as tap water. If you decide to use it, though, you’ll need to adjust the pH as required. 

As you may have guessed by now, the most important thing is to test the water, no matter the source. Feed the plants only when you determine that the water is suitable for your plants or you’ll have a lot of headaches in the long run. 

Summary: Why is Water Quality Important While Growing Cannabis?

We’ve already posted a ton of best practices that you can follow to improve your cannabis plant’s health and yield. But if you want to go a step further, you need to ensure the water you use is high quality. 

So, make sure the water you use has the right levels of TDS and pH, and if not, take the recommended measures to ensure it meets the ideal range requirements. The process is fairly easy but it adds another level of safety for your plant’s health. 

Do this right and you’ll even notice an improvement in your plant’s health and yield over time. But this isn’t the only thing you need to work on. Growing cannabis is art and there are several other methods you can use. Stay tuned for more.