Reverse Osmosis Water Filter System Parts & Components Explained
Written by: Gene Fitzgerald // Last Updated: Aug 15, 2023
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A reverse osmosis system consists of many parts and components.
If you’ve ever wondered what these parts do, this article is for you.
Here, we talk about all the different reverse osmosis water filter components and their functions. Keep reading to learn all about them!
Contents
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Key Takeaways
The key parts of a reverse osmosis system are:
- Feed water valve
- Pre-filters
- Reverse osmosis membrane
- Water storage tank
- Carbon post-filter
- ASO valve
- Check valve
- Flow restrictor
- Drain saddle
- RO faucet
- Tubing
Optional components for a reverse osmosis system include:
- Water pressure pump
- Permeate pump
- Remineralization post-filter
- UV post-filter
- TDS monitor
- Pressure regulator
Reverse Osmosis Water Filter System Parts and Components
There are two types of reverse osmosis system components; the standard/essential parts and the optional components. The standard parts are required in all RO systems, while the optional components offer additional but not strictly necessary features.
Note: This article explains the parts and components that apply to under sink RO systems.
Standard Reverse Osmosis Parts Explained
Below are the standard components and parts of the classic under sink reverse osmosis system:
Feed Water Valve
The feed water valve is the part of the RO system that connects it to the sink’s cold water supply. The water supplied to the system flows through the feed water valve before it proceeds to the first filtration stage.
Pre-Filters
The RO system passes water through two or more pre-filter stages before pushing it through the semipermeable membrane. The pre-filters remove suspended sediments, chlorine, and other chemicals that are harmful to said RO membrane.
Sediment Pre-Filters
Sediment pre-filters remove silt, dust, sand, rust, and other dirt from the water before it reaches the semipermeable membrane. This means the membrane is exposed to fewer contaminant particles and protected from harm.
Sediment pre-filters are also used to protect water softeners and UV disinfectants.
Carbon Pre-Filters
Like sediment pre-filters, carbon pre-filters are designed to eliminate as many contaminants as possible before the water reaches the reverse osmosis membrane. Activated carbon protects the RO membrane from harmful chlorine and provides thorough filtration results.
Reverse Osmosis Membrane
This is the main component in any reverse osmosis system and removes the most contaminants from water.
The RO membrane contains really small pores (0.0001 microns in size). These super tiny pores reject contaminants, allowing only pure water molecules to pass through them. The filtered or rejected contaminants are flushed out of the membrane as waste water.
Water Storage Tank
After purifying water, the RO system stores it in a pressurized water storage tank. Reverse osmosis is a slow process, so a storage tank ensures water is available whenever you need it.
RO systems continuously filter water until the storage tank is full — that way, there’s always water available, and you don’t have to wait hours for a glass of water.
Carbon Post-Filter
In a standard RO system, water is filtered through a carbon post-filter after it has been stored in the tank.
The carbon post-filter is usually the last stage of water purification, and it helps to further improve the quality of water. It removes residual chlorine and other contaminants from water, giving it that finishing touch it needs to be completely contaminant free. It also improves water taste.
ASO (Automatic Shut-Off) Valve
The automatic shut-off valve (ASO valve) stops the RO system from endlessly filtering water when the storage tank is full. The valve is automatically activated when the tank is full, preventing the system from sending more water to the RO membrane and down the drain.
When you open your faucet and use water from the storage tank, the pressure drops, deactivating the ASO valve and allowing water to resume its flow.
Check Valve
The check valve is designed to prevent water flow from the storage tank back to the RO membrane. The ASO and check valves only work when they’re used together.
Flow Restrictor
The function of the flow restrictor is to restrict the flow of waste water in the RO system. It keeps the pressure at a level that allows the system to work efficiently, preventing excessive waste water production.
Drain Saddle
The drain saddle connects the system’s waste line to the under sink drain pipe. It’s important for sending waste water out of the system.
RO Faucet
The sole function of the RO faucet is to dispense filtered water. RO faucets are typically made of high-quality plastic and/or non-corrosive metal. They feature a small lever or button that is pulled to dispense water.
Filter Housings and Brackets
The filter housings hold the filter elements in a reverse osmosis system. They allow you to replace the filter cartridges conveniently.
Brackets are helpful because they provide a stable and secure positioning for the RO system. Using a bracket ensures the system is secure and less likely to get damaged and manhandled. Having the RO system on a bracket also allows you to access the system’s components easily during maintenance.
Fittings
RO quick-connect fittings are used to attach tubing quickly and securely. The fittings are usually color-coded to tell you how the tubes should be connected.
Tubing
The tubings are what link all the parts of the RO system together.
Mounting Clips
RO mounting clips are small clips designed to secure RO filters membranes. They fit tightly around the filter or membrane housing and hold them in place.
Mounting clips come in different shapes, sizes, and styles, depending on the type of RO model.
Optional RO System Components
These optional RO components provide extra features like boosting system efficiency.
Water Pressure Pump
A water pressure pump or booster pump is recommended for RO systems that don’t have enough feed water pressure. RO systems work best with pressure at around 60 psi. You must install a booster pump if your feed water pressure falls below 40 psi.
Permeate Pump
Permeate pumps are installed into RO systems to improve efficiency and reduce waste water production. Permeate pumps work by storing the waste water in a chamber and then using it as energy to push purified water into the storage tank.
This process stops the pressure in the tank from pushing against the RO membrane, making the system more efficient.
Further Reading:
Remineralization Post-Filter
Reverse osmosis filters strip water of any foreign bodies. Unfortunately, this means beneficial minerals are also removed from the water. To solve this problem, remineralization post-filters add trace amounts of minerals like calcium, zinc, sodium, and magnesium into the filtered water, greatly improving its taste and nutritional benefits.
UV Post-Filter
An RO membrane is not designed to remove microbes from water. This is because the microorganisms can multiply and accumulate on the membrane eventually slipping through.
UV post-filters are placed after the other filter stages to remove bacteria etc. from the water. They kill microbes by attacking their DNA with UV light, effectively stopping them from functioning.
TDS Monitor
A TDS monitor is a less common optional feature in RO under sink systems. They are installed on a smart faucet and provide a reading of the TDS level in purified RO water. TDS monitors tell you if your system is getting rid of TDS just fine or if you need to change the reverse osmosis membrane.
Pressure Regulator
RO systems work under high pressure, but too much pressure can damage the filter cartridges and their housings. A pressure regulator protects the system from sudden rises in pressure.
Under Sink Reverse Osmosis System Diagram
Under sink reverse osmosis systems save countless people from drinking contaminated water. Below is a diagram of such a system showing the different parts and components and how they work.
If you have any questions about reverse osmosis water filter components please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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