pH of Water for Cannabis: How to Make Your Crops Thrive

The pH of Water for Cannabis

What Should the pH of Water for Cannabis Be?

Growing cannabis requires a lot more effort than simply putting seeds into the ground and coming back a few weeks later. Everything needs to be done just right in order to get the yield you’re looking for, as well as the potency of the individual plants.

One thing you may not realize is an important component of this is the water. The pH of water is a crucial measurement concerning tap water quality. That is what we are going to focus on in this article.

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Importance of pH when Watering Cannabis Plants

Your cannabis plants don’t just need water, they need the right kind of water. City water, pond water, well water or river water, every source is different. You will know whether or not the water is right for your plants by looking at the pH levels. Before we go into why it is important to measure the pH, let’s break down exactly what this measurement is telling us.

What is pH?

pH testing

The United States Government’s science website tells us that pH is a measure of how acidic or alkaline (base) water is. The pH scale goes from 0 to 14, with a pH of 7.0 being neutral. pHs of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base. pH is a measure of the relative amount of free hydrogen and hydroxyl ions in the water.

The pH of water determines the solubility, the amount that can be dissolved in the water, and biological availability, the amount that can be utilized by aquatic life of chemical constituents. This includes nutrient solutions like phosphorus, nitrogen, carbon, calcium, and magnesium, as well as heavy metals like lead, copper, and cadmium. Both excessively high and low pHs can show pH problems and impact your ability to use the water.

For cannabis plants, water within the right pH range is important because it affects the form of the nutrients in the substrate. If pH is low, the solubility of some micronutrients like iron and manganese increases. This makes them more available to plants and causes toxicity.

What’s the Ideal pH of Water for Cannabis?

Ideal pH of Water for Cannabis

All plants require nutrients. Healthy plants require the macronutrients phosphorus, nitrogen and potassium. They also need micronutrients and minerals including copper, iron, magnesium, calcium, and much more. If the pH is not right, the plants may not be able to take in these nutrients, even if the nutrients are present in the substrate. This can cause nutrient deficiencies by nutrient lockout. 

Balancing pH is a critical component to ensuring nutrient solubility and uptake for cannabis. Cannabis tolerates a wide pH range (5.0-7.0) without the yellowing of top leaves. Any pH levels outside of the optimal range (5.8 – 6.2) will limit growth, though. This means using a pH tester is needed.

While the pH for cannabis needs to be just right, pH fluctuations are normal. In order to maintain optimal pH levels, experts recommend that you undergo pH testing every two days, and adjust the pH as needed. Don’t worry, though, digital pH meters, and pH testing kits will tell you everything you need to know.

Measuring pH:

Maintaining and monitoring your plants’ pH can result in healthier plants and higher yields. This means keeping a vigilant eye on the pH is very important. Checking the pH often, and adjusting when needed, will ensure your plants are within an optimal range.

You can check your pH with a digital pH pen for checking the pH in soil, or a digital pH meter for measuring the pH in the water. You can also use a manual pH kit. These kits come with strips or drops. When adding the water to them they will change to a specific color. This color will indicate the level of your pH. 

Substrate pH levels that drop below 5.0 result in increased micronutrient availability. This can lead to iron toxicity, manganese toxicity, or both. This toxicity can stunt your plant’s growth. Yikes. Substrate pH levels that become too high make micronutrients, such as iron, unavailable to the plant, even when there are adequate levels present in the substrate. 

Cultivators using soil as their medium should adjust their pH to a range of 6.0 to 7.0. For a grow that is using hydroponics or soilless media, pH is much more of an important issue. Without soil, there is no buffer, therefore pH fluctuations can occur quickly. The pH for these methods should be between 5.5 to 6.5.

Correcting PH

When corrections need to be done, they should be done slowly. Large swings in pH can stress your plants. Adjusting your pH may sound scary, but it can be a very simple process. Using proprietary pH Up and pH Down solutions can give you reliable results each time.  

Increasing: To increase the pH, you will need to add something alkaline to balance it out. For soil, you can use pH up with water and flush with it. Limestone, wood ash, bonemeal, and baking soda can also help increase your pH. With hydroponics, use pH Up with potassium hydroxide or potassium carbonate in it.

Decreasing: To decrease the pH, you will need to add something acidic to balance it out. pH Down, sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid, and low pH salts will do the trick. More organic ways to decrease pH are vinegar, citric acids, sawdust, or woodchips. 

Always be cautious when using pH correctors, and be sure to always refer to the material safety data sheet (MSDS) before handling each. Click the names above to be directed accordingly. Since the formulas for pH Up and pH down can vary with different suppliers, follow the MSDS on the supplier’s website. We used Advanced Nutrients above for reference.

Advice for Growing Cannabis

Whether you need more information on understanding a pH meter, pH of water for cannabis, selecting the right watering products, making better use of your space by ditching batch tanks, or anything else- we’re here for you!

Eden Water Technologies has mastered all levels of water treatment. The Paragon is setting the bar HIGHer and so is our team! Be sure to check back for more informative guides on cannabis and water treatment.


  • • Checking your pH often should be a part of your plant care. Every 2 days is recommended. 
  • • There are many solutions when it comes to adjusting your pH. But take it slow!
  • • The pH at the root zone of your cannabis plant determines how well the plant will take in the nutrients and minerals. 
  • • There are several methods for measuring pH. Find your preferred method.
  • • pH needs to be adjusted differently depending on your substrate.
  • • Maintaining proper pH can lead to healthier plants and high yields.


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