Which Water is Best For Weed Plants? How Can You Test and Adjust Water Quality?


As we all know, water is an essential thing for every living thing to survive on this planet, and this is very much applicable to plants as well. Together with light and nutrients, water plays a vital role in keeping the plants healthy and thriving. Water also transports and brings all the nutrients that are required for healthy plant growth. Aside from carrying the nutrients, water is also a significant component when it comes to achieving the soil’s right pH balance.

Given the contributions that water has when it comes to growing plants, it is also reasonable that the quality of water that you will be using will directly affect the final result or the final plant produce. Therefore, to arrive with a bunch of high-quality buds and flowers, as a grower and cultivator, you have to make the most out of the nutrients you are giving your plants. To effectively do it, you have to be sure that the water you are using is the best one for your weed plants. This post will help you decide which water will be best for your plants and how to test for its qualities.

Why does water quality matter?

We all know that water is something that we can find everywhere; as a matter of fact, Earth is made up of 71% water. But, water is not all the same and is not created equal in terms of composition. Water is more than just simple hydrogen and oxygen; and it also contains tons of minerals and other microorganisms. Some of these elements are essential for plant growth, while some water has already been treated, with chlorine, for example, to cancel out all the bacteria and elements found in water.

When growing cannabis, you must be sure that the water you will be using will be beneficial to your plants and help them grow to become healthy cannabis plants.

Hard water and soft water

There are two kinds of water in general, hard water and soft water – hard and soft water differ in the number of minerals they contain. Hard water contains higher levels of concentration when it comes to tracing minerals such as calcium and magnesium. Trace minerals are incorporated into the water as the water flows over rocks and soil. Since the mineral deposits are relatively high, the pH of hard water can become slightly alkaline. Because of its high pH, hard water is not very ideal for cannabis growth.

On the other hand, soft water has lower concentration levels of minerals, therefore making the pH neutral to acidic in most cases. Soft water also has higher salt content but not that high that it can be dangerous to humans and plants.

Hard water can be treated to become soft water; however, this is done through chemical methods. That is why treated soft water is not recommended for garden-use since the chemicals used can cause damage and might be detrimental to plant health.

Water options for your weed plants

We will be giving you more specific water types that you can use for growing your cannabis plants. This will help you identify which water will work best for you according to your living conditions, location, and water accessibility.

Tap water

This type of water is considered the most common and most frequently used because of its accessibility. Using tap water might need you to check on a few things before you start watering your cannabis plants. You may have to consider the place where you live and know the water supply of your area, and you should be able to check this with your local waterworks office or your town officials.

Tap water can be hard or soft and may contain certain compounds to keep that water flowing clear. It may also contain chlorine and fluoride in some cases, which will not be healthy for your cannabis plants. If you have no other choice but to use tap water, you may have to collect water and let it sit in your tank for 24 hours so that minerals and other compounds can settle to the bottom of your tank. You can also use an osmosis filter to clean your water to make it potable.

Distilled water

Distilled water is commonly sold in drug stores and grocery stores. This type of water does not contain any microorganisms; that is why it is commonly used for human consumption. Distilled water can certainly be used for plants; however, it is not recommended for permanent and continuous plant consumption since it has no minerals at all as well. Also, before using it for your plants, you might need to add calcium and magnesium.

Reverse osmosis water

Reverse osmosis water is comparable to distilled water; however, it is not as pure; therefore, not every mineral is eliminated. Water that is being filtered through reverse osmosis has less than 0.4 EC and a pH of around 7.0. With its purity and minimal mineral content, you can surely use reverse osmosis water without the need to modify it at all. This type of water is believed to be the best type for your cannabis plants.

Air conditioner water

As the name implies, air conditioner water is the water you get from your air conditioning system. Some people may consider air conditioner water as waste, but let me tell you, you can use this to water your cannabis plants, but we recommend that you use an EC meter depending on how old your air conditioning unit is or the specs of your unit.


Rainwater is basically water that you can collect from rain. You can quickly put up a rainwater collection tank, store it and use it later on. Because of today’s environmental conditions, rainwater is not generally potable anymore; however, it can water almost all types of plants. To obtain rainwater and maintain it to its high quality, you will have to keep your collection tank as clean as possible to avoid elements that could decrease the quality of your rainwater.

Reservoir or spring water

Before collecting water from a reservoir, wells, or springs, you have to be sure that the area is not contaminated so that the water composition is excellent. This is important since there are possibilities that the reservoir can be contaminated with chemical insecticides or mineral fertilizer. This type of water can also contain large amounts of pathogens such as bacteria, fungi, viruses, and parasites. You can make sure that your water source is good through studies that have been made in that area; if there are no studies yet, it is not ideal that you will be using that water source then.

Mineral water (bottled)

Bottled water is designed for people to drink and can be a good option for some cannabis growers if they have nothing else to use. You can be confident that mineral water contains zero harmful substances at all. To be able to use mineral water, you need to pick a brand with the lowest amounts of minerals and an appropriate pH.

Best Water for Weed Plants

After going through the types of water that you might be able to use for your weed plants, you may have already chosen one that can best fit you according to your lifestyle, resources, and location. Based on each water’s description and the pros and cons, the best ones for your weed plants are reverse osmosis water and distilled water. These two types of water are guaranteed to have no harmful substances or contaminants that can negatively affect your weed plants.

Adjusting and correcting water dilemmas

It is not a new condition that cannabis growers often experience problems with the quality of water they are using for their crops. The most common issues start because of the high concentration of minerals present in water; fortunately, there are convenient ways to fix them.

High sodium content

High sodium concentration can cause damage your cannabis plants, and extremely dry soil with too much sodium can be deadly. To resolve this issue, you can feed your plants with filtered water to dilute the high sodium concentration. For a long-term solution, you can improve the soil drainage and use well-balanced water instead.

Sulfur content

You can easily smell sulfur in your water, and sulfur can cause acidity, which can eventually weaken your cannabis plant. You can always use a pH meter to check, and if confirmed, you can add lime to your soil to make it less acidic.

Chlorinated water

Most tap waters have been treated with chlorine, and its high concentration can be detrimental to your cannabis plants. High chlorine content can also cause a nutrient burn. To fix this, you can make use of activated carbon filters to remove chlorine. Also, you can always let your water sit overnight. A long-term solution will be using reverse osmosis water.

Good water makes happy weed plants.

In conclusion, you have to make sure that the water you are using is of good quality and free from contaminants and unwanted substances. Good quality water is vital so that your cannabis plants can grow healthy and bloom with potent flowers and buds. We hope that this post has helped you decide which water to use on your cannabis plants and made you confident that you are giving them the best water they need.

Testing and Adjusting Water Quality

  1. pH Levels: Cannabis prefers a pH of 5.5-6.5 when grown hydroponically and 6-6.8 in soil. Testing can be done using digital meters or drop-based kits. Adjust pH levels using pH up or down solutions, or natural alternatives like vinegar and baking soda.
  2. Temperature: Ideal water temperature for cannabis is between 68°F and 73°F. Water that’s too warm or too cold can harm the plants.
  3. Mineral Content (PPM): The Parts Per Million (PPM) measures the mineral content of water. Ideal PPM levels vary throughout the plant’s lifecycle, generally ranging from 500-1100 PPM. Test PPM with TDS meters.
  4. Hard vs. Soft Water: Hard water, typically found in wells, contains more minerals than soft water. Adjusting the mineral balance may be necessary depending on the source.

Advanced Testing and Adjustments

  1. Water Quality Analysis: For a detailed understanding, submitting a water sample to a qualified water analysis laboratory is recommended. This can help identify any factors that may affect plant health.
  2. Filtering and Treatment: Depending on the water source and quality, different filtration and treatment methods like reverse osmosis, deionization, or acid injections can be employed to achieve the desired water quality.


Emphasize the importance of regular water testing and adjustments for healthy cannabis growth. Highlight how water quality can significantly impact nutrient availability, plant health, and yield.