What is Reverse Osmosis?
Source: WikipediaReverse osmosis (RO) is a membrane-technology filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side.
How Does Reverse Osmosis Work?
In the normal osmosis process, the solvent naturally moves from an area of low solute concentration (High Water Potential), through a membrane, to an area of high solute concentration (Low Water Potential). The movement of a pure solvent to equalize solute concentrations on each side of a membrane generates osmotic pressure. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis. The process is similar to other membrane technology applications. However, there are key differences between reverse osmosis and filtration. The predominant removal mechanism in membrane filtration is straining, or size exclusion, so the process can theoretically achieve perfect exclusion of particles regardless of operational parameters such as influent pressure and concentration.
Reverse osmosis, however, involves a diffusive mechanism so that separation efficiency is dependent on solute concentration, pressure, and water flux rate. Reverse osmosis is most commonly known for its use in drinking water purification from seawater, removing the salt and other substances from the water molecules.
The efficiency of a reverse osmosis water filter is affected by the water pressure coming into the system and the temperature of that water. Membranes are tested at 65 psi of pressure and temperature of 77 degrees. For each incremental change in either variable, membrane performance changes accordingly. Higher pressures increase production and vice versa. The optimal pressure is 65 PSI and temperature is 77°, as seen here on our reverse osmosis pressure/temperature chart.
Stages in a Reverse Osmosis System
Below is a simplified and exploded diagram of a typical 4-stage reverse osmosis system. The stages have been numbered and the arrows show the directional flow of the water as it moves through the system. A larger diagram of the membrane is featured at the bottom to show its many layers, the component of the system that makes it a ‘reverse osmosis’ system.
1. Sediment Pre-Filter
Melt Blown Polypropylene removes dirt, rust and sediment particles down to 5 microns. There are several different types of sediment cartridges.
Pleated filters feature increased surface area and longer life. These cartridges are washable and reusable.
Melt blown polypropylene filters are designed for the removal of dirt, rust and sediment from water. 5 and 20 micron are the most popular sizes for drinking water applications.
String wound filters are an inexpensive solution to your filtration needs. These cartridges come in a variety of media types and have a wide range of applications.
2. Carbon Pre-Filter
Coconut Shell Carbon Block Cartridge(s), 10 Micron removes chlorine, taste, odor and chemical contaminants.
Activated carbon block filters typically have a 0.5 to 10 micron filtration capability, making it also helpful for particulate filtration, removing taste and odor from chlorine, insoluble lead reduction, and demonstrating, in some cases, removal of Giardia and Cryptosporidium. A 5-stage reverse osmosis system has an third housing to hold an additional carbon block cartridge.
3. Reverse Osmosis Membrane
Thin Film Composite (TFC) rejects (removes) 95% of Total Dissolved Solids (TDS) down to .0001 Microns.
Thin film composite membranes (TFC or TFM) are semi permeable membranes manufactured principally for use in water purification or water desalination systems. They also have use in chemical applications such as batteries and fuel cells.
4. Post Carbon Filter
Coconut Shell Activated Carbon is the final polishing filter after storage tank, just before you use the water.
Inline post filters typically clip onto the top of a reverse osmosis system’s membrane housing. The post filter removes any chlorine or contaminants missed by the other cartridges or membrane.
What Can Be Removed From Drinking Water?
The reverse osmosis process can remove a myriad of organic and inorganic contaminants from your tap water.
These systems specialize in removing chlorine taste and odor, rust, sediment and also alleviate common worries about public water by reducing or completely removing arsenic, asbestos, chromium, fluoride, lead, mercury, VOCs, THMs, giardia and cryptosporidium. For a more expansive list, view our contaminants removed by reverse osmosis list or our thin-film membrane particle size removal chart above.
What Makes Up a Reverse Osmosis System?
The following components make up your reverse osmosis system:
Reverse Osmosis Module
The RO module is the main component and holds the pre-filters and membrane, and post filter. A bracket is provided so they can be mounted under the sink or in a basement.Feed Water Valve (Angle Stop Adaptor)
Feed water valve connects to the cold water line to supply water to the RO system. This valve comes in several different types. An angle stop valve screws onto the cold waater line directly above the cold water shut-off valve. A faucet adaptor connects to the cold water line just below an existing faucet. A self-piercing valve clamps onto the cold water line and makes a small puncture in the pipe.Pre-filter #1
Melt Blown Polypropylene filter removes larger particles such as dirt, rust & sediment.Pre-filter #2 (And #3 If Applicable)
10 Micron Carbon Block removes chlorine and chemical contaminants in the feed water and protects the RO membrane.Automatic Shut-Off Valve
Automatic shut-off valve closes when the storage tank is full and shuts off the water supply to conserve water. The valve activates when the tank pressure is 2/3 of the feed pressure.Membrane
Reverse Osmosis Membrane Thin Film Composite Membranes reduces dissolved minerals, metals, and salts. In this process, harmful compounds are separated by the membrane from the water, and the contaminants are flushed to the drain.Drain Valve
Wastewater saddle valve connects to the drain to remove reject water from the RO system.Post Filter
A coconut shell activated carbon post filter is provided for a final “polish” and to remove tastes, odors and to provide great tasting water.Bladder Storage Tank
Bladder tank holds RO purified water, ready to use.Drinking Water Faucet
The RO Faucet is used to dispense purified water when you want it.Tubing
Tubing connects all RO components.Quick-Connect Fittings
Quick-Connect fittings are used for necessary tubing connections. See: Instructions for Quick-Connect Fittings.
Our Reverse Osmosis Systems
A boil-water advisory or boil-water order is a public health advisory or directive given by government or health authorities to consumers when a community’s drinking water is, or could be, contaminated by pathogens.
Learn how to make an emergency water filter for disaster situations out of some common items.
This method does work and can keep you heathly if clean potable water or a manufactured water filter system are unobtainable.
The Hydrologic Cycle (also called the Water Cycle) is the continuous movement of water in the air, on the surface of and below the Earth.
This cycle is the exchange of energy which influences climate. When water condenses, it releases energy and warms the environment.
90% of the garbage floating in the Earth’s oceans is plastic and less than 5% of all plastic is recycled.
The patch mostly consists of pelagic plastics, formed from plastic bags, plastic water bottles, bottle caps and styrofoam.
Hydraulic fracturing (sometimes referred to as fracking or hydrofracking) is a relatively new form of natural gas extraction.
The fluids used in the fracking process flow back to the surface, often entering the water table or polluting the drilling area, and sometimes improper disposal of waste water from the wells.
As our technology advances, so do new forms of pollution and contaminants that effect our environment and our health.
Read more about drinking water contaminants and their health effects.
Chlorine has long been recognized as an oxidative agent, meaning that it not only kills the germs in the water supply; it will damage any living tissue with which it comes in contact. And your skin, like the rest of your organs, is living tissue. But that’s not the only problem.
Since the discovery of its health benefits in the mid-1940’s, fluoride is often added to the public water supplies of industrialized countries in order to reduce the populations tooth decay, which is especially effective in low income communities, where good dental hygiene may be too costly.
Chromium-6 was found in the drinking water supply of the southern California town of Hinkley and brought to national attention by Erin Brockovich.
The EPA is reviewing effects of Chromium-6 after a recent report brought to light dangerous levels in a number of major US cities.
Giardia is a flagellated protozoan parasite that colonizes and reproduces in the small intestines of humans and other animals, which can cause giardiasis.
Symptoms of Giardiasis usually show after 3 to 4 days, and include gastrointestinal and constitutional problems.
Cryptosporidiosis is a disease caused by the parasite Cryptosporidium parvum.
Since a outbreak in 1993 in Wisconson, new attention has been focused on determining and reducing the risk for Cryptosporidiosis from community and municipal water supplies.
What is reverse osmosis? What is a 4-Stage system? What are the components in a system? Visit our ‘How Reverse Osmosis Works‘ guide to find the answers.
Also see out list of contaminants RO removes and comparison chart for particle sizes to learn more about reverse osmosis.
What is ultraviolet light? Do I need to filter the water before the UV process? How exactly can light kill organisms?
Visit our ‘How Ultraviolet Purification Works‘ guide to find out how it works.
The typical water softener is a mechanical appliance that’s plumbed into your home’s water supply system. All water softeners use the same operating principle: They trade the minerals for something else, in most cases sodium. The process is called ion exchange. More…
Step by step instructions on installing replacement cartridges and sanitizing filter housings. It is highly recommended that you clean and sanitize your system once a year.
Need help installing your new RO system, how to perform maintenance, or how often to change your cartridges?
View our printable Reverse Osmosis Installation Guide to learn more.
Step by step instructions on making a connection with Quick-Connect fittings. Quick-connect fittings allow you to connect and disconnect tubing without the need of tools. For larger, plumbing size fittings read our using twist lock guide.
Step by step instructions on making a connection with Twist and Lock fittings. Twist-Lock fittings allow you to connect and disconnect tubing without the need of tools.
Step by step instructions on making a connection with SharkBite Push-To-Connect fittings. SharkBite fittings allow you to connect and disconnect pipes without the need of using PVC glue or welding copper.
Need to filter water but not sure about the differences between or applications of our systems?
Use our Water Filter Systems Guide to find out which system is best for your filtration needs.
Need to replace your system’s cartridges but not sure what type is best for your system?
View our Cartridge Replacement Guide or contact us to find out what you need.
View a chart comparing the specifications of all the reverse osmosis systems we sell on this site. All bladder tanks are NSF certified.
The size of your water softener depeneds on the total grain per day that need to be removed.
This is determined by the number of people in your household, grain per gallon (GPG) hardness and the amount of Iron present in the water.
A micron is a unit of measurement for how small of particles a filter will catch. The lower the micron size, the tinier the ‘holes’ in the filter cartridge are that allows water to pass through, ranging from 0.1 absolute to 150 microns.
Use our Pore Size Efficiency Guide to find out what micron size to use.
Pleated sediment cartridges remove dirt, rust and sediment from water while providing an increased surface area and longer life. Pleated filters down to 5 microns are washable and reusable.
Use our Pleated Sediment Cartridge Comparison to find the filter cartridge you need.
Aquariums need three types of filtration to maintain a healthy environment for freshwater, saltwater or amphibian aquariums (sediment filtration, carbon filtration, and removal of biological contaminants).
When traveling around the state or the country in a RV you might not always know where you will be getting the water from or what might be in it. Water that is stored in a RV holding tank will not stay potable for long and can become a breeding ground for algae and bacteria.
Chemicals added to public water supplies, like chlorine, can be harmful to the living cells of plants.
When brewing beer with tap or bottled water, chlorine and chloramine present in the water can combine with malt phenols in the wort to create a compound called chlorophenol, which can give the beer a medicinal taste.
View our Filtered Water for Home Beer Brewing guide.
Bottled water requires a lot of resources to manufacture and ship, and costs a lot more than reverse osmosis water.
Use our Bottled Water Cost Calculator to find out how much of an impact you have on the environment.
