Reverse osmosis (RO) is a water filtration method commonly used to treat drinking water. RO has become popular due to its effectiveness in removing a wide variety of contaminants from water. This filtration type is also very economical as most RO water filtration systems cost about $350.
Although the term "reverse osmosis" sounds complex, the methodology is quite simple. In this article, we'll explain how the reverse osmosis process works, and what components are used in a typical under-sink RO drinking water system.
The real "heart" of a reverse osmosis system is the RO membrane. The membrane works by utilizing household water pressure to force tap water through a semi-permeable membrane.
As the water is pushed through the membrane, the clean water is sent to a holding tank through one tube, and the contaminants are separated out flushed away down another tube.
The real "heart" of a reverse osmosis system is the RO membrane. The membrane works by utilizing household water pressure to force tap water through a semi-permeable membrane.
As the water is pushed through the membrane, the clean water is sent to a holding tank through one tube, and the contaminants are separated out flushed away down another tube.
What are the Stages of a Reverse Osmosis System?
At first glance, an RO system might look complex with all of it's tubes, housings, fittings, tank, etc. But the system is actually quite simpe. A reverse osmosis filtration system generally has 3, 4 or 5 stages.
All reverse osmosis systems will include an RO membrane, but the number of pre/post filters can vary between systems. Below we define the stages of a typical RO unit.
SEDIMENT FILTER Sediment, silt, and dirt are filtered out in this RO prefilter. This is especially important because sediment can damage the delicate reverse osmosis membranes.
CARBON FILTER Next, water enters the carbon filter. This filter has the ability to remove various contaminants that affect the performance and life of the RO membrane
REVERSE OSMOSIS MEMBRANE The RO membrane is the "heart" of the RO system. This is where water is pushed through a semi-permeable membrane allowing purified water through to a storage tank, but holding back contaminants that are flushed away.
POLISHING FILTER In a four-stage RO System, a final carbon filter (or post filter) will “polish” off the water to improve the water's taste and odor.
Because the reverse osmosis method filters water through these stages slowly, water is sent to a holding tank. This way, you have plenty to use when you need it.
What to Consider Before Purchasing an RO System?
As you select an RO drinking water unit, you'll find that systems and models vary in three basic ways:
Amount of water the system can filter each day. For example, a "50 GPD" system means it should be able to produce 50 gallons of filtered water per day
Number of filtration stages
Quality of components
Also, before purchasing a system, you may want to consider the cost of replacement filters. Some makes/models have very expensive replacement filters.
To help customers save money, we bundle high-quality replacement filters together in one simple kit. While these filters are not "brand name" filters, they're top-of-the-line filters gauranteed to produce the same high-quality drinking water you'd expect from OEM filters.
With some models, only expensive OEM filters can be used. In this case, many of our customers have converted their existing RO system with a new "manifold unit" to hold the filters, but kept their same tank and faucet.
Why Choose Reverse Osmosis?
If you're searching for a water filtration system that will give you outstanding water. Here area few reasons to consider RO:
Improves Taste RO filtration improves taste, odor and appearance of water by removing contaminants that cause taste and odor problems.
Saves Money With an RO system, you can cancel your water delivery service and stop purchasing cases of bottled water. Reverse Osmosis filtration provides “better-than-bottled water” quality water for just pennies per gallon.
Simple Maintenance RO systems have very few moving or replaceable parts make RO systems easy to clean and service.
Removes Impurities Reverse osmosis systems can remove common pollutants from water including nitrates, leadpesticides, sulfates, fluoride, bacteria, pharmaceuticals, arsenic and much more. An Reverse Osmosis systems’ carbon filter will also remove chlorine and chloramines.
Find Out Why Milions OF Households Have Reverse Osmosis Drinking Water Systems
Top-Selling Reverse Osmosis Drinking Water Systems
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Advanced Filtration, Quick-Change Filters, & Conserves Water
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Reverse Osmosis Frequently Asked Questions
What does a reverse osmosis system actually remove from tap water?
A reverse osmosis system removes a wide range of contaminants from drinking water, including lead, fluoride, pesticides, nitrates, Arsenic 5, sulfates, pharmaceuticals, and dozens of others. The RO membrane filters fine particles, while the pre- and post-carbon filters also eliminate chlorine, chloramines, and the contaminants that cause bad taste and odor — delivering filtered, better-tasting water than most bottled water brands.
How does the reverse osmosis membrane work?
The RO membrane is the core of any reverse osmosis filtration system. It works by using your home's existing water pressure to push tap water through a semi-permeable membrane. Clean, purified water passes through to a storage tank, while dissolved contaminants and impurities are separated out and flushed down the drain. No electricity or chemicals are needed — just standard household water pressure.
What's the difference between a 3-stage, 4-stage, and 5-stage RO system?
All reverse osmosis systems include a sediment filter, a carbon filter, and an RO membrane as the core stages. A 4-stage system adds a post-carbon "polishing" filter that improves the final taste and odor of your drinking water. A 5-stage system may add an additional carbon block or specialty filter. More stages generally means more thorough filtration and better-tasting water.
Is reverse osmosis water safe to drink every day?
Yes — reverse osmosis water is safe and healthy for daily drinking. RO filtration produces exceptionally pure water by removing harmful contaminants like lead, Arsenic V, and nitrates. RO water is widely used in households, restaurants, and commercial facilities as a trusted source of high-quality drinking water.
How much does it cost to run a reverse osmosis system at home?
A residential RO drinking water system typically costs around $350 upfront, and produces filtered water for just pennies per gallon — far less than bottled water. The main ongoing expense is replacing filters, which should be done every 6–12 months depending on your water quality and usage. Choosing a system with affordable, widely available replacement filters (rather than expensive OEM-only filters) significantly reduces long-term costs.
How long does it take a reverse osmosis system to filter water?
A reverse osmosis system filters water slowly — typically producing 25 to 75 gallons per day depending on the system's GPD (gallons per day) rating. Because the filtration process takes time, RO systems store purified water in a holding tank (usually 3–4 gallons) so that clean water is immediately available when you turn on the faucet. A 50 GPD system is sufficient for most households.
How often do reverse osmosis filters and membranes need to be replaced?
Pre-filters (sediment and carbon) should be replaced every 6–12 months to protect the RO membrane and maintain water quality. The RO membrane itself typically lasts 2 years, depending on your water quality and usage. A post-carbon polishing filter should also be replaced annually. Staying on a regular filter replacement schedule ensures your RO system continues to deliver safe, great-tasting drinking water. ESP Water makes replacements easy, with subscription opportunities and reminder emails.
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