What is a Reverse Osmosis System and How Does it Work?

Widely regarded as one of the most effective methods of water filtration, reverse osmosis (RO) produces clean, great-tasting water. RO systems are used in a variety of applications including electronics, pharmaceuticals, hotels, government sewage works, restaurants, and desalination. No matter what kind of water you start with, there may be an RO system that fits your needs. Below you will find what reverse osmosis systems are, their benefits and uses. You can also find a list of the best reverse osmosis systems on the market.
 

What is reverse osmosis?

Reverse osmosis removes contaminants from unfiltered water, or feed water, when pressure forces it through a semipermeable membrane. Water flows from the more concentrated side (more contaminants) of the RO membrane to the less concentrated side (fewer contaminants) to provide clean drinking water. The fresh water produced is called the permeate. The concentrated water left over is called the waste or brine.

A semipermeable membrane has small pores that block contaminants but allow water molecules to flow through. In osmosis, water becomes more concentrated as it passes through the membrane to obtain equilibrium on both sides. Reverse osmosis, however, blocks contaminants from entering the less concentrated side of the membrane. For example, when pressure is applied to a volume of saltwater during reverse osmosis, the salt is left behind and only clean water flows through. 


How does a reverse osmosis system work?

Reverse osmosis equipment is to pass the raw water through fine filter, granular activated carbon filter, compressed activated carbon filter, etc., and then pressurize it through pump, with an aperture of 1 / 10000 μ M (equivalent to 1 / 6000 of the size of E. coli and 1 / 300 of the size of virus), the reverse osmosis membrane (RO membrane) changes the water with higher concentration into the water with lower concentration. At the same time, it isolates all the impurities mixed into the water such as industrial pollutants, heavy metals, bacteria and viruses, so as to meet the physical and chemical indexes and health standards specified for drinking and produce clear to pure water. It is the best choice for human body to supplement high-quality water in time Because the purity of water produced by RO reverse osmosis technology is the highest among all water production technologies mastered by mankind at present, and the cleanliness is almost 100%, people call this kind of water production machine reverse osmosis purified water machine.
Reverse osmosis equipment applies membrane separation technology, which can effectively remove charged ions, inorganic substances, colloidal particles, bacteria and organic substances in water. It is the best equipment in the process of high-purity water preparation, brackish water desalination and wastewater treatment. It is widely used in electronics, medicine, food, textile, chemical industry, power generation and other fields.


Composition of reverse osmosis equipment system:
Generally, it includes pretreatment system, reverse osmosis device, post-treatment system, cleaning system and electrical control system.
The pretreatment system generally includes raw water pump, dosing device, quartz sand filter, activated carbon filter, precision filter, etc. Its main function is to reduce the pollution index of raw water and other impurities such as residual chlorine, so as to meet the influent requirements of reverse osmosis. The equipment configuration of the pretreatment system shall be determined according to the specific conditions of raw water.
The reverse osmosis device mainly consists of multi-stage high-pressure pump, reverse osmosis membrane element, membrane shell (pressure vessel), support, etc. Its main function is to remove impurities in the water and make the effluent meet the use requirements.
The post-treatment system is added when the reverse osmosis cannot meet the effluent requirements. It mainly includes one or more equipment such as anion bed, cation bed, mixed bed, sterilization, ultrafiltration, EDI, etc. The post-treatment system can better improve the effluent quality of reverse osmosis and make it meet the use requirements.
The cleaning system is mainly composed of cleaning water tank, cleaning water pump and precision filter. When the reverse osmosis system is polluted and the effluent index cannot meet the requirements, it is necessary to clean the reverse osmosis system to restore its efficacy.
The electrical control system is used to control the normal operation of the whole reverse osmosis system. Including instrument panel, control panel, various electrical protection, electrical control cabinet, etc

What does a reverse osmosis system remove?
A reverse osmosis system removes dissolved solids like arsenic and fluoride through the RO membrane. An RO system also includes sediment and carbon filtration for a broad spectrum of reduction. The carbon filters in an RO system remove chlorine and bad taste and odors, and the sediment filter removes dirt and debris

Does a reverse osmosis system remove…

Fluoride? Yes.
Salt? Yes.
Sediment? Yes.
Chlorine? Yes.
Arsenic? Yes.
VOCs? Yes.
Herbicides and pesticides? Yes.
Many other contaminants? Yes. The contaminants listed are some of the most popular ones treated with an RO system, but the system also removes a slew of other contaminants.
Bacteria and Viruses? No. If your water comes from a city treatment plant, then it should already be microbiologically safe. Reverse osmosis may remove some bacteria, but bacteria could grow on the membrane and potentially enter your water supply. To remove living organisms and viruses, we recommend UV disinfection.
Learn how to remove bacteria from your drinking water. 

Reverse osmosis system benefits
A reverse osmosis system is one of the most extensive methods of filtration. It removes 98% of dissolved solids, which makes it healthier to drink. A water distiller is the only other drinking water system that also reduces TDS, but it's less efficient than an RO system. 

Harmful dissolved contaminants reduced
Sodium reduced 
Bad tastes and odors reduced
More environmentally friendly than bottled water
Easy to install and maintain
Browse Reverse Osmosis Systems
 

Where to use a reverse osmosis system

Under the sink? Yes.

Reverse osmosis is most commonly installed at the point of use (POU), like under a kitchen or bathroom sink. A point-of-use RO system could also be mounted in a cabinet or remotely in the garage or basement. 

For a refrigerator? Yes.

Connecting an under-sink reverse osmosis system to your refrigerator is simple and worthwhile. Reverse osmosis removes minerals from water, making your ice clear and beverages more refreshing. 

For the whole house? Rarely.

Reverse osmosis can be used to treat water for the whole house. However, unless your water has a specific contaminant that requires reverse osmosis, using an RO system may be over-kill. An RO system solves specific problems like saltwater intrusion in a well or high levels of silica in the water.

An RO system will not provide the flow rate needed to pressurize an entire house. In the rare case where a whole house requires RO water, a large booster pump, like a Grundfos or Davey, provides adequate water pressure. In addition to a large water pump and storage tank, a UV system is needed to disinfect the water once it leaves the tank.

Homeowners have a lot to consider when purchasing an RO system for the whole house. If your water quality is dire enough to warrant whole house reverse osmosis, you likely have other water quality issues that will need to be addressed prior to the water reaching the RO membrane. High levels of water hardness will cause scale build-up on the membrane, reducing its performance and causing it to fail prematurely. Contaminants like iron can also foul the membrane and will need to be eliminated from the water before being treated by the reverse osmosis system.

If you believe your water quality may require whole house reverse osmosis to treat, check out our in-depth guide on reverse osmosis systems. 

For showers? No.

If you don’t want to purchase a storage tank larger than your basement, reverse osmosis is not the best option for your shower. The solution is usually much simpler and more focused than reverse osmosis. Shower water with high levels of chloramines can cause nose and eye irritation and aggravate skin conditions. Chloramines are best removed by a whole house catalytic carbon filter. 

Hard water can also lead to unsatisfying showers. Soap does not lather well in water with elevated mineral content, and hard water can leave hair feeling lifeless and dull. An ion exchange water softener will eliminate these contaminants. 

For pools? No. 

The only time you may need an RO system for a pool is if the water contains some contaminant that no other filtration system can remove. If you try to fill a 20,000-gallon pool with RO water, even with the most efficient system, you will send 10,000 gallons down the drain. Good news: the amount of dissolved solids in a pool doesn’t really matter, so other systems do a better job providing clean pool water.

For agriculture? Sometimes.

Reverse osmosis works well for hydroponic farming, but not all plants survive or thrive with RO water. RO is best suited for greenhouses where plants are misted or in small gardens, depending on the types of plants. Since hydroponic farming eliminates soil, and instead nurtures fruits and flowers with only nutrient-rich water, high-quality water is paramount to hydroponic success. Even small amounts of sediments, salts, and dissolved organics can upset the delicate balance of the plant life. RO water allows for total control over your plants nutrient intake.

Explore how to use reverse osmosis water for hydroponics. | Learn more about how hydroponic systems work.

For wells? Yes.

If you get your drinking water from a private well, then an RO system is an excellent way to ensure that the water flowing to your tap is safe. A reverse osmosis system is a perfect way to remove difficult contaminants often found in well water, like nitrates.

In apartments? No.

One point-of-entry unit usually supplies water to an apartment building or condominium, and installing an under-sink system is often not allowed. A countertop filter system is the best option in an apartment. 

| If you're looking to invest in a countertop filter, explore our countertop filter buyer's guide. |

At businesses? Yes.

Commercial or industrial reverse osmosis systems are common because commercial units allow drain water to be sent back into the feed supply. Reverse osmosis removes paints, dyes, and other industrial contaminants well. 

For an aquarium? Yes.

If you’re a saltwater fish enthusiast, then an RO system is perfect for you. Reverse osmosis allows you to strip all minerals from the water and add exactly the amount of salt you need back in with a remineralizing filter. Most aquarists rely on a combination of reverse osmosis and deionization (known as RO/DI water) to ensure their fish are immersed in highly pure water, modified to match the fish's natural environment.

| Learn more about why you should use reverse osmosis water in your aquarium. | 

In RVs? Yes.

RO systems require proper draining. Storage tanks are difficult to attach to RVs because drain hookups aren’t located at campsites, but it is possible. A reverse osmosis system can be very helpful for those whose RV adventures take them into more remote, wilderness locations. A combination of RO and ultraviolet disinfection can make sure the water you are drinking is free from harmful bacteria and particulate matter. 

| Explore our RV water filters buyer's guide. |

 

How long do reverse osmosis systems last?

Reverse osmosis systems usually last between 10 and 15 years. While the systems themselves have a long lifespan, the RO membrane and filters need replacing periodically. The prefilters and post filters should be changed every 6 months to 1 year. Depending on your water conditions, the RO membrane should be replaced every 2-4 years.

Here are a few tips to help you maintain your reverse osmosis system.