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How Does a Reverse Osmosis System Work?

Hydroponics would likely be a lot more difficult on a commercial scale if reverse osmosis systems weren’t used to purify water before entering the growing environment.

You might not know much about these systems, but they ensure that the nutrient solution provided to plants doesn’t include contaminants or organic matter that might disrupt the internal operation of the hydroponic system.

In this blog, we’ll discuss how reverse osmosis systems work, why they’re important for hydroponics, and provide you with some important things to keep in mind when using one of these systems.

What is a Reverse Osmosis System?

A reverse osmosis (RO) system is a water purification technology that uses a semipermeable membrane to remove impurities from water. In this process, water is forced through the membrane, which allows only water molecules to pass through while blocking contaminants.

The result is purified water on one side of the membrane and concentrated impurities on the other. Reverse osmosis is commonly used for improving the quality of drinking water, desalination of seawater, and various other applications.

Reverse osmosis removes up to 99% of chlorine, up to 100% of heavy metals and salts, and removes sediment, inorganic salts, microorganisms and organic material from source water, making it ideal for use in hydroponic growing systems.

A reverse osmosis system inside a hydroponic shipping container farm.
Reverse osmosis systems have several filters, which work to reduce the amount of dissolved solids in the source water, providing hydroponic systems with a standardized water quality that’s ready for the addition of nutrients.

Why Is Reverse Osmosis So Important for Hydroponics?

Before water can be used in a hydroponic system, it requires the addition of plant-supporting nutrients. However, we can’t just add nutrient solution to the water that pours from the tap, because the quality of water changes depending on regional factors.

Think of an RO System’s purpose as preparing input water for the addition of nutrient solution. In an efficient, productive hydroponic system, you’ll target specific nutrient concentrations and pH levels. Start the process by ensuring that the water you provide for your plants is purified before combining it with nutrient solution.

Breaking Down the Layers of a Reverse Osmosis System

It can be difficult to understand a reverse osmosis filter without cracking into it and examining each of its parts. Let’s explain how one of these systems works by looking at each stage of the filtration process.

A Quick Note On The RO System We’ll Be Examining

For this specific breakdown, we’ll be looking at Hydrologic’s StealthRO 150 Customized Reverse Osmosis Filter. While you may be using a different system, it’s likely to be similar, with slight differences in number of filters and purified water to brine water ratio.

Our head grower prefers this system over others that we’ve tested because it produces significantly less brine than other systems, increasing the amount of purified water that can be used for hydroponics.

Stage One: Reducing Sediment, Silt, Rust & More

The first stage sends water through a pleated, cleanable sediment pre-filter. It can filter out particles as small as 5 microns, taking the largest impurities out of the water. This stage plays a key role in the Reverse osmosis process, as it removes the worst impurities that would otherwise degrade the filters of the following stages.

Regularly check this filter’s performance every six months. If you notice that the flow rate is reduced, you may need to clean and replace it. If issues persist, you may need to adjust your water pressure or examine the other filters for wear.

Stage Two: Removing Chlorine & Other Toxins

Next, the water will flow through the carbon filter, which is a carbon block made using coconut shell Greencarbon. It removes major contaminants like chlorine and carbon, and can make water look visibly clearer by removing turbidity.

These filters should be replaced for every 1,250 gallons of purified water produced.

Stage Three: Reduces PPM of Total Dissolved Solids

Finally, the flow enters the last stage of the reverse osmosis process. The membrane is a semipermeable barrier that selectively allows certain molecules, ions, and particles to pass through while blocking others.

The RO process results in two streams: purified water and brine (concentrate or reject water). For this system, the ratio of these two is 1:1, though ratios of 1:2 pure water/brine and 1:3 pure water/brine are common with other RO systems.

As water passes through the RO membrane, contaminants such as dissolved salts, minerals, bacteria, viruses, and other impurities are effectively blocked and separated from the water. These contaminants are typically larger in size than water molecules.

You must clean these filters regularly, and then change them out every 6 months or 12 months, depending on the intensity of use.

After this process, the water has been sufficiently purified, but along with the bad minerals, plenty of minerals that are useful for plant development have also been removed. Because of this, you must mix nutrient solution into the water, test the pH of the solution, and make any required changes to optimize it for your specific crop.

What is Brine? Can You Use It for Anything?

The brine generated from a reverse osmosis (RO) system, also known as wastewater or concentrate, contains the impurities and contaminants that were removed from the feed water.

While you can’t use this water in hydroponics because of its increased mineral content, you can use it for outdoor crops or for washing dishes and automobiles. Just add an equal amount of tap water to dilute the mixture’s mineral content before use.

The brine disposal pipe of a reverse osmosis system that's housed inside a hydroponic shipping container farm.
Brine is expelled from the system through a pipe, though this water can be used for other purposes, like washing a car or cleaning windows.


In conclusion, reverse osmosis (RO) systems are integral for the success of commercial hydroponics, ensuring that water is purified before entering the growing environment. These systems play a critical role in preventing contaminants and organic matter from disrupting hydroponic operations.

The RO process, through several stages of filters, effectively removes impurities like chlorine, heavy metals and sediment, making water suitable for hydroponic use.

While the resulting brine is unsuitable for hydroponics due to increased mineral content, you can find other uses for it after dilution.

Overall, RO systems are indispensable in providing purified water for optimal plant growth in hydroponic systems, highlighting their importance in the success of large-scale hydroponic operations.

Curious about getting started with hydroponics? Pure Greens manufactures and sells pre-designed and custom hydroponic shipping container farms, which enable growers to cultivate crops regardless of outside climate conditions. Contact us, and we can discuss how we can assist your hydroponic operation.

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