Watering Cannabis Plants: The Complete Guide

Watering cannabis plants is the fuel for the plants, carrying energy through its stem. Just like humans sweat to cool down, your plant’s leaves release water for the same reason. How good your water is, and what’s in it, plays a big role in how well your cannabis plants will grow. So, it’s crucial to have good quality water for a successful crop.

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

Consistency is very important when it comes to growing cannabis. You will need to monitor and maintain your water quality all the time!

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 he use, and what else their plants may need. From our experience, there are 4 popular sources of water for growing cannabis. We are going to dive into each one and how it’s treated, as well as the pros and cons of each.

Popular Sources of Water for Grow Cannabis

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 water 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 BiG Plant Science nutrients 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

Tap water is usually fine for your cannabis plants, just like it is for your houseplants. It has minerals and ions that are good for plants. But there’s a catch – tap water often has chlorine, which can be harmful to soil and affect cannabis growth. The good news is that chlorine in tap water usually evaporates on its own or can be left in an open container for 12 to 24 hours before using it for soil-grown plants.

For hydroponics, tap water might not be the best choice because you can’t control the minerals in it. Filtering might be necessary. But if you’re growing a few plants in soil at home, tap water is okay. Just check and adjust the pH to avoid nutrient issues.

Using BiG Plant Science nutrients with tap water is simple – measure, shake, and feed your plants. It makes taking care of your plants easy!

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 is a good in-between 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.

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 its 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.

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.

What is EC, PPM, and TDS (Total Dissolved Solids) and why you should monitor them?

When preparing 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.

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. BiG Plant Science nutrients contain all the essential nutrients for cannabis growth and can be used easily with each one of these water sources.