The Basic Component of a Reverse Osmosis System


While the RO process may seem complex, it is actually made up of a few simple components that work together to purify water.

This article will explore the basic components of a RO system in detail and explain the role of each component in the overall system. By understanding the basic components of a reverse osmosis system, you can make the most informed decision when selecting a filtration solution.

What is the Reverse Osmosis System?

Figure 1 reverse osmosis drinking water systems

A reverse osmosis system is a filtration technique that uses a thin but finely woven semipermeable membrane to remove contaminants from water. It is a popular choice for industries, marine ships, pharmacies, and homes to improve the quality of their drinking water. However, choosing a system that is right for your needs is essential. Fortunately, there are several reverse osmosis systems on the market, so you can compare features and prices before purchasing.

Basic Parts of an RO System

Reverse osmosis (RO) removes our come by forcing raw water through a semi-permeable membrane by pressure. Most RO systems are made up of a number of basic components, including:

1. Feed Water Inlet Valve

The feed water inlet valve is a component that controls the flow of water into the RO system. It is typically located at the beginning of the RO process before the water passes through the RO membrane. The feed water inlet valve is an important component because it helps to regulate the flow of water into the system and ensure that the RO process is operating at optimal efficiency. There are several types of feed water inlet valves that can be used in an RO system, including ball valves, gate valves, and globe valves. The type of valve used will depend on the specific requirements of the RO system, such as the pressure and flow rate of the feed water.

Figure 2 RO system with a pretreatment unit.

2. Pretreatment Unit

A pretreatment unit is a component of a reverse osmosis (RO) system that prepares the feed water for RO filtration. The role of the pretreatment unit in the entire process is to reduce damage to the reverse osmosis membrane by removing contaminants in the raw water that could foul or damage the membrane in advance.

The specific design of the pretreatment unit will depend on the nature of the feed water and the intended use of the purified water. In general, however, a pretreatment unit will typically include one or more of the following components:

  • Coarse filters

These are typically used to remove large particles such as sand, gravel, and other sediments. Coarse filters may be made of materials such as polypropylene or stainless steel, and they may be used in conjunction with a backwash system to clean the filter media.

  • Fine Filters

These filters are used to remove smaller particles such as algae, protozoa, and other microorganisms. Fine filters may be made of materials such as polypropylene, cellulose, or ceramic, and they may be used in conjunction with a cartridge or bag filter to capture smaller particles.

  • Disinfection Unit

This unit is used to kill or inactivate any microorganisms that may be present in the feed water. Disinfection may be accomplished using chemicals such as chlorine or ozone, or by using UV light.

This component is used to remove hardness ions such as calcium and magnesium from the feed water. Softening may be accomplished using a variety of methods, including the use of ion exchange resins.

water Softener

3. High-Pressure Pump

A high-pressure pump is a key component of any (RO) system. It provides the pressure required to force water through the semi-permeable membrane of the RO system. The high-pressure pump is typically driven by an electric motor and is designed to operate at high pressure, typically between 40-80 bar (600-1200 psi).

The pump works by drawing in water from the feed water source and then using its impeller to accelerate the flow of water and increase the pressure. This high-pressure water is then sent through the RO membrane, where impurities are removed as the water is forced through the small pores of the membrane.

4. Reverse Osmosis Membrane

The RO (Reverse Osmosis) membrane is the decisive component in the overall reverse osmosis system. It is typically made of a thin layer of polyamide, a synthetic polymer, which is sandwiched between two layers of the thin film. The polyamide layer is the active layer that does the actual filtration, and the thin film layers provide structural support. The RO membrane works by allowing water molecules to pass through it while blocking larger contaminants such as bacteria, viruses, and dissolved minerals.

The pore size of the RO membrane is typically around 0.0001 microns, which is small enough to remove most contaminants from water. The RO membrane is usually housed in a cartridge or module, which can be easily replaced when necessary. It is important to maintain and replace the RO membrane regularly to ensure that it is functioning properly and producing high-quality purified water.

RO Membrane

5. Storage Tank

The water storage tank, as the name implies, is used to store the pure water produced by the RO membrane. It is a pressurized container in a reverse osmosis (RO) system. The storage tank usually supports various volumes of water and is made of materials that are safe for drinking water, such as stainless steel or high-grade plastic.

In some RO systems, the storage tank is equipped with a float valve, which helps to maintain the water level in the tank. When the water level in the tank falls below a certain point, the float valve opens to allow more water to enter the tank. This helps to ensure that the storage tank is always full and ready to dispense water when needed.

Storage Tank

6. Post Treatment Unit

A post-treatment unit is a component of a reverse osmosis (RO) system that is used to further treat the RO-purified water before it is made available for use. The purpose of the post-treatment unit is to ensure that the purified water meets all the necessary quality standards and is safe for drinking, cooking, and other household uses. There are several different types of post-treatment units that can be used in an RO system, depending on the specific needs and requirements of the system. Some common post-treatment units include:

1) Carbon Filters

The carbon filter removes any remaining impurities or contaminants missed by the RO membrane. The strong adsorption characteristics of activated carbon are used to adsorb impurities and remove various contaminants such as chlorine, chemicals, and bad odors.

2) UV Sterilizer

This type of post-treatment unit uses ultraviolet (UV) light to kill any remaining bacteria or viruses that may be present in the purified water. UV light disinfection is a very effective way to ensure that the purified water is safe for consumption.

UV Sterilizer

3) pH Adjustment Unit

Some RO systems may include a pH adjustment unit to adjust the pH of the purified water to a more neutral level. This is important because water with a high or low pH can have a negative impact on the taste and quality of the water.

7. Dispensing Valve

In a reverse osmosis (RO) system, the dispensing valve is a component that controls the flow of water from the RO system to the point of use (e.g., a sink, or drinking water faucet). It is typically located after the storage tank in the RO system’s water distribution line. The purpose of the dispensing valve is to regulate the flow of water and ensure that it is delivered at a consistent rate and pressure to the point of use.

8. The Control Board

The control board is a key component of a reverse osmosis (RO) system that helps to regulate and monitor the various functions of the system. It is essentially a central processing unit that controls and coordinates the various parts of the RO system. The control board typically has a number of inputs and outputs that allow it to receive information from sensors and other components within the system, as well as control various functions such as the operation of pumps and valves.

Figure 4 RO system control board.

It may also have a display or user interface that allows the operator to monitor the system and make any necessary adjustments. In addition to controlling the basic functions of the RO system, the control board may also be programmed to perform more advanced tasks such as monitoring water quality, adjusting the flow rate, and performing self-diagnostic checks. Some control boards may also be able to communicate with external devices such as computers or smartphones, allowing for remote monitoring and control of the RO system.

9. Membrane Cleaning Skid

A purge skid is usually a separate unit connected to the reverse osmosis system that contains the necessary equipment and chemicals to clean the membranes. It may include tanks for storing cleaning chemicals, pumps for delivering the chemicals to the membrane, and control systems for regulating the cleaning process.

How Does a Basic Reverse Osmosis System Work?

To understand the reverse osmosis system, you must understand osmosis. Osmosis, in simple scientific terms, is the natural diffusion of solvent molecules (usually water or other solvents) through a semipermeable membrane. In this case, the water molecules move from a higher to a lower concentration through the semipermeable membrane.

So, reverse osmosis, as the name suggests, is the opposite of osmosis. In the reverse osmosis system, a pressure force directs water in the opposite direction through a semipermeable membrane. Therefore, water moves from a higher to a more diluted concentration. The reverse osmosis system effectively uses pressure to remove impurities and contaminants from water.

Now, here is how the basic reverse osmosis system works:

Reverse Osmosis Systems work flow


1. Pre-filtration

Before water enters the reverse osmosis membrane, it goes through the pre-filters. These filters separate larger sediments and particles, chlorine, chemical components, and other substances that can damage the semipermeable membrane.

2. Pressurization

Remember that the reverse osmosis system uses pressure. So, it pressurizes water using a pump. This pressure is necessary to override the natural osmosis force so that water passes through the semipermeable membrane.

3. Semipermeable Membrane

This membrane is a tightly woven mesh sheet that forms a semipermeable barrier. The pores on the mesh allow water molecules to pass through but block larger molecules, including contaminants and ions. As water goes through the semipermeable membrane, contaminants cannot pass through.

4. Disposal

The contaminants that do not make it through the semipermeable membrane form a concentrated brine solution. Brine, or rejected water, is flushed out of the system, thus preventing its re-entry into the purified water system.

5. Collection

The now-purified water is collected and stored in a storage tank. At this level, the water is ready for use. Sometimes, purified water can undergo further treatments, including disinfection and remineralization, to improve taste and quality.

Benefits of the Reverse Osmosis System

Figure 1 Reverse osmosis systems

● Reduced Contaminants

Unlike other water filtration systems, the reverse osmosis system is considered residential-grade. Reverse osmosis filters can extract about 99% of lead, radioactive agents, industrial chemicals, heavy metals, and 80 other contaminants. Consequently, the reverse osmosis filters are microscopic, so they can successfully remove large and dissolvable contaminants.

● Eco-friendliness

If you are an environmental enthusiast, reverse osmosis is a more environmentally friendly option when compared to other water filtration techniques. The system is safer as it prevents the accumulation of plastic.

● Improved Taste

Water purified through the reverse osmosis system may be more beneficial for household use. The US water systems explain that the reverse osmosis systems contain fewer minerals. As a result, aquatic pet owners with pets that require fewer minerals may want to consider using water that has undergone reverse osmosis filtration.

Cons of the Reverse Osmosis System

● Expensive Installation and Repair

While the reverse osmosis system is highly beneficial and practical, it may be costly on a large scale. Similarly, the cost of repair and maintenance can be expensive too. Also, even though you can consider installing the system yourself, it can be a complex process.

● Strips Water of Essential Minerals

The system can also strip purified water of essential and healthy minerals, thereby reducing the pH value of the water. A reduction in water’s pH value makes it more acidic and corrosive.


Although several users agree that the reverse osmosis system is effective, it is also wasteful. For example, the reverse osmosis system wastes 4 gallons of water for every purified gallon.


In the above post, we have provided a thorough overview of the key components that make up a reverse osmosis system. These components include the pre-filter, reverse osmosis membrane, storage tank, and post-filter. Each of these components plays a critical role in the overall effectiveness and efficiency of the reverse osmosis system, and it is important to understand how they work together to produce clean, purified water.

If you are stranded on where to procure any part from, worry no more because NEWater has you covered. We manufacture and supply A-List RO components with warranty covers and our prices are unbeatable.

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