What Type Of Water Do You Use for Growing Cannabis?

Water. We all need it. It’s essential for all life on earth, and cannabis plants are obviously no exception.

Water is what your plant uses to transport energy through the stalk and your plant’s leaves will release water to help cool them down, much like human sweat. The quality and contents of your water will determine the overall success of your cannabis crop.

So how do you make sure you’re giving your plants quality water?

Consistency is important when it comes to growing cannabis, and due to its crucial, water is one of the things you will need to monitor and maintain.

What a lot of new growers don’t think about is the type of water they are feeding their plants. Water is more than just a couple of hydrogen atoms attached to oxygen. Water contains many numerous natural minerals and sometimes added chemicals like chlorine which is used for treatment purposes.

A grower should have a good idea of what exactly is in the water they are feeding their plants and what else their plants may need. From my experience, there are 4 popular sources for growing cannabis. I’m going to dive into each one and how it’s treated, as well as the pros and cons of each.

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Reverse Osmosis

Reverse osmosis (sometimes called RO for short) is a method of water filtration that involves forcing water through a partially permeable membrane that removes ions, minerals, and larger particles. These filters strip the water of pretty much everything, leaving nearly pure water behind. These are the type of filters typically used by hydroponic growers.

Hydroponic cannabis growers enjoy having this clean slate to work with. They start with stripped water and then add nutrients and adjust pH as needed to reach their ideal water composition.

Since the reverse osmosis process strips away any minerals and salts you might get some wacky results if you measure the pH right after filtering. pH meters need ions to measure and without minerals, they won’t work properly. So add your nutrients first then measure the pH.

Using a product like Reefertilizer Grow and Bloom in RO water for hydroponic or soil growing will help you maintain a proper balance of the essential nutrients for cannabis growth during veg and flower.
Reverse osmosis and other membrane filters are usually more expensive than other methods. They also require a little maintenance as well since the filters need to be cleaned and replaced every so often.

Tap Water

Good old tap water – it’s good enough for your house plants and, in most cases it’s good enough for your cannabis too! Tap water contains charged ions, minerals, and added chemicals like chlorine. Chlorine is an important part of tap water, making it safer by killing small organisms that can make us sick. Unfortunately, left-over chlorine can also hurt living organisms in soil, which has the potential to affect your cannabis growth.
But there’s good news! In most modern water systems the chlorine is dissipated by the time it comes out the tap. Chlorine is also volatile, meaning that it evaporates easily. 

If you’re a cannabis grower using soil, then you may want to allow any extra chlorine to evaporate before you water your plants. To do this simply leave that tap water out in an open container for 12 to 24 hours to let the chlorine escape. In most cases tap water doesn’t contain enough chlorine to hurt organic soil, so letting it evaporate is just precautionary, but it’s an easy way to avoid harming microbes in your soil.

Tap water isn’t the best choice for hydroponics because the grower has no control over what type of minerals exist in the water, or at what concentrations. Some areas might have heavy water that needs to be filtered before using on your weed plants.
But if you’re growing a few plants in soil at home, tap water is perfectly acceptable. Just be sure to monitor and adjust the pH for cannabis to avoid any nutrient problems.
Reefertilizer Grow and Bloom are easy to mix into tap water and make feeding your plants a breeze. Just measure the right amount of powder, shake it up, and feed your plants, simple as that.

Bottled Water

Bottled spring water is generally taken from a natural source and then filtered by any number of methods. Most bottled water is essentially the same as tap water, with the same potential for unknown minerals, ions, and chemicals. Using spring water to feed your plants is expensive and doesn’t offer many benefits over tap water, and I don’t really recommend it because of the overall cost, but wanted to mention it because I once had a friend who used it to feed his clones and seedlings.

The only significant benefit I can think of using bottled water would be its consistent PPM value and pH. Also, if you had a flood or your water disconnected then it could potential save your plants.
Distilled water is another expensive water source available as bottled water to give your plants. Similar to reverse osmosis, distilled water is stripped of ions, minerals, and contaminants, offering a clean slate like RO water but with a potentially steep price tag.

Carbon Filtered Water

Carbon filters are used to purify water by removing many impurities and contaminants through a process called adsorption. Carbon filters are made of activated carbon, which is a form of carbon that has been treated with oxygen to create a network of tiny pores and a high surface area. These pores are what make the carbon effective at adsorbing many impurities from water.
A carbon filter jug (like a Brita) is a good inbetween straight tap water and reverse osmosis.

A carbon filter is going to help remove some chlorine and minerals from your water making it a good choice for some growers depending on their water source. If you live in an area where your tap water is a little hard, a carbon filter might be all you need.

What is PPM, EC, and TDS (Total Dissolved Solids)?

When evaluating water to use for your cannabis plants, these measurements will give you a clue about the mineral content of your water. Water with minerals will conductive to electricity, and the more mineral and salts in your water the better it will conduct electricity. By using this information we can estimate the volume of minerals in water.
EC stands for electrical conductivity and can be measured with a specialized tool. These tools will sometimes use a formula to estimate the PPM (parts per million) and TDS (Total Dissolved Solids). What they won’t tell you is what minerals or other elements are in your water.

Learn how to measure PPM and grow better weed…

Natural Water Sources

You can potentially tap into natural water sources to feed cannabis plants. There are a few things you should know before giving lake or rain water to your cannabis plants. At first it might seem like the natural way to feed any plant, but let’s think first about quality of natural water sources. Mother nature provides water for plants through rain and groundwater.

Rain is a lot like distilled water. Water evaporates from waterbodies leaving behind many minerals and contaminants. It then rains down on the soil, and filters through dirt while on it’s way to feed hungry plant roots. Rain water can be slightly acidic, so if you plan to collect and use it keep an eye on the pH. You may need to use agricultural lime to raise pH.

Water in the soil usually comes from a lake, river, or swamp. The soil acts as a filter and removes many large particles and organisms while enriching the water with a number of nutrients and minerals.
Open water sources will likely contain many small organisms and potential pests to plant life. If you put it directly on your plants there’s a potential it might harm your plant or cause infection. You could first filter it and boil it to remove any harmful contaminants but that’s time consuming and costly.
The mineral content of naturally sourced water is also difficult to predict and will depend on the geology and location of the water source. A water report for you well source would be a helpful tool to determine what time of filtration is necessary.
A very easy and natural way to grow weed is to plant it directly in the soil next to a river bed. The soil will be natural nutrient rich and consistently moist, lowering the amount of hand watering you would have to do.

After filtering a natural water source you will want to add nutrients to feed your cannabis plant. Using Reefertilizer Bloom or Grow will help ensure your plants are getting the essential nutrients needed for a great harvest.

Some folks will make what’s called “compost tea” which is a lot like it sound like. What you do is steep a permeable bag filled with compost in a barrel of water (perhaps rain water). You would want to aerate the liquid as it steeps with an air pump or an airstone if you’re fancy. The air prevents it from becoming stagnant and prevents less desirable bacteria to grow.


I hope this article helps clarify the different types and source of water available to feed your cannabis plants. These sources range in cost and benefits. Regardless cannabis will need the right combination of water and nutrients to grow healthy and potent flowers. Reefertilizer nutrients contain all the essential nutrients for cannabis growth and can be used easily with each one of these water sources.
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Thanks for reading! If you have any questions or comments, send us an email or fill in the comment box below. Grow good weed!

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