How Does Reverse Osmosis Work? The Ultimate Guide
If you’ve ever taken a sip from a glass of water that came from the home of someone with a reverse osmosis system, you know how pure and refreshing it tastes.
Or, perhaps you have concerns about water quality and want to make sure your family is drinking healthy water that reduces contaminants as much as possible.
Reverse osmosis (R.O.) drinking water truly is the purest choice for any home. It’s water the way nature intended us to drink it.
But how exactly do these systems work, and what do they do to your home’s water?
What is Reverse Osmosis?
Most homeowners have likely heard of reverse osmosis before, but unless they already have a system in their home, they might not know exactly what it is or how reverse osmosis works. Reverse osmosis is one of the most refined methods of water filtration, and it can improve water quality and taste, even when the water is already treated.
To understand reverse osmosis, let’s start with defining osmosis. According to Brittanica, osmosis is the process of water or other solvents passing through a semipermeable membrane wherein particles are held back by the membrane. Normal osmosis naturally always travels from the highest concentration of water to the lowest concentration. When thinking about osmosis in action, consider how the roots of a plant draw water and nutrients from the soil — this process of the roots drawing the nutrients and water through the soil is osmosis.
At its base level, the reverse osmosis process is similar to osmosis, involving molecules moving through a semipermeable membrane to filter out water contaminants. However, the primary difference is that reverse osmosis requires an external pressure to force the water through the membrane because it is doing the opposite of what is found in nature. The unfiltered water has a lower concentration of pure H2O versus the higher concentration on the opposite side of the filtration membrane. So in order for the water to flow through the system, it needs to be pushed by external forces. The reverse osmosis membrane blocks contaminants large and small, leaving the fresh, uncontaminated water on one side of the membrane and the contaminants on the other side.
When thinking about reverse osmosis with regard to the water in your home, the reverse osmosis membrane in the reverse osmosis system acts like a type of filter as it has extremely tiny pores that help remove microscopic contaminants from the water you drink by straining them out. In the case of reverse osmosis drinking water systems, the semipermeable membrane only lets water molecules through while other contaminants are collected and flushed away. The result is high quality filtered water to drink that is free from contaminants, fresh, and delicious!
Now that we know the basic definition of osmosis and reverse osmosis, let’s dig in and learn about reverse osmosis water filtration systems for home use, when it’s needed, how it works, and if it’s right for your home.
Why Do I Need a Reverse Osmosis System?
Reverse osmosis is a great option for those who have water softeners or other filtration systems (such as a fixture-mounted carbon system) that aren’t quite meeting the homeowner’s needs. Some individuals may be perfectly happy with the result of hard water that is softened, whereas others seek out a more crisp, filtered, bottled water type of taste.
Additionally, some systems cannot filter out contaminants the way a reverse osmosis system can. Reverse osmosis, also known by the shortened “RO” systems, are able to capture contaminants that other systems miss. We have reverse osmosis drinking water systems that are tested and certified for reduction of:
- nitrates and nitrites
- chromium (hexavalent & trivalent)
- cyst (cryptosporidium)
- total dissolved solids (TDS)
Soft water is excellent for cleaning, showering, and laundry. However, some people would rather not drink it. Depending on how hard your water is to start with, it could still have high total dissolved solids (TDS), which can negatively affect the taste. The reason is that the hard minerals are replaced by sodium, and there may be other contaminants in your water that a softener will not remove.
A reverse osmosis system can remove the undesired sodium along with other contaminants and dissolved solids, which makes a water softener and a reverse osmosis system an ideal combination for most homes.
How Does a Reverse Osmosis Filtration Work?
Although we previously simplified the definition of reverse osmosis, there’s a bit more to the process when using a reverse osmosis system to purify drinking water.
Reverse osmosis systems have three cylindrical canisters on a manifold, where one is the reverse osmosis membrane and the other two are carbon filters. Let’s take a closer look at the purpose of each of the three filtration stages and how they function in a reverse osmosis system.
Step 1: Pre-filtration
The first step in purifying water with a reverse osmosis drinking water system is meant to protect the membrane. It removes larger sediment, including some dissolved solids, and helps reduce chlorine that may be in your water. This first cartridge is referred to as the sediment filter or carbon block filter. It helps conserve the membrane, which can get clogged by excess sediment or damaged by exposure to too much chlorine, which you’ll find in municipal water.
Step 2: The Reverse Osmosis Membrane
Following the initial filtration comes the real magic of a reverse osmosis system. Your water is forced through the semipermeable membrane under pressure. The reverse osmosis membrane is a synthetic plastic material that allows the passage of water molecules. However, sodium, chlorine, and calcium as well as larger molecules like glucose, urea, and cysts cannot pass.
Water-Right often uses thin film composite (TFC) membranes. which are resistant to bacteria breakdown and have a high rejection rate of 95 to 97 percent on average. TFC membranes are not chlorine-resistant, which is why a carbon prefilter is used.
Steps 3 & 4: Post Filtration and Final Polish
Before your home’s water is ready to drink, it goes through a second carbon filter (or post filter), which removes any remaining contaminants in the unlikely case they slipped past the first two steps in the system. Then the water fills up a storage tank where it waits until you’re ready to use it. Finally, there’s the in-line activated carbon filter, which gives your water one last polish as it comes out your faucet. This is used to remove any remaining odors or flavors that may come from the system hoses or the holding tank while your water is waiting to be used. The polish is a “just in case” step to make sure the water you drink tastes incredibly fresh!
How Much Space Do I Need For a Reverse Osmosis System?
Reverse Osmosis systems take up relatively little space in your home. Unlike larger systems like water softeners, reverse osmosis systems can take up very little space; however, it is dependent on the specific reverse osmosis system you choose. Reverse osmosis drinking water systems are commonly installed under kitchen sinks or can be mounted in basements underneath the sink you want it to connect to so you don’t have to sacrifice your cabinet space. Whole house reverse osmosis systems are a little larger and are typically installed near the point your water enters your home, like a water softener or water heater do. Whole house systems are commonly installed in a basement or utility room. Keep in mind that sacrificing a small amount of space will bring forth big rewards in the form of better tasting water, cost savings, and more!
What Maintenance is Required With a Reverse Osmosis System?
Just like with any water filtration system for home or for an appliance in your home, it is important to properly maintain it. Properly maintained reverse osmosis systems can last for as long as a decade or even longer!
When you have a reverse osmosis system installed in your home, the installer should review the proper maintenance and maintenance schedule of your equipment. The frequency of how often you will need to replace your carbon or membrane cartridges will depend on how many contaminants you are needing it to collect and how much water you will run through the system.
The pre-filter or sediment filter should typically be changed on a yearly basis as this filter protects your reverse osmosis membrane, but your local professional may recommend it be done every 6 months for high usage homes. Properly taking care of this filter means your membrane should last a two to three years before it will need to be replaced. The carbon filter should be replaced about once or twice a year depending on your water quality.
Is Reverse Osmosis Drinking Water Right for Your Home?
When you install a reverse osmosis system, you’ll enjoy better-tasting coffee and tea, clearer ice cubes, and pure, healthy water right from your kitchen sink. If you’re still using bottled water for drinking, you’ll be able to make the switch to drinking from your tap. A reverse osmosis system is a smart investment that saves you money in the long run and is better for the environment. If desired, Water-Right also offers whole home reverse osmosis systems. You can even wash your car with reverse osmosis water for a spot-free finish!
Get further details on reverse osmosis drinking water systems complete the form below to get connected with one of our local water experts in your area for your free in-home consultation!