5-Stage Reverse Osmosis System Diagram

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Ever wondered how a 5-stage reverse osmosis system works in detail?

In that case, this article is for you.

Our 5-stage RO system diagram explains it all!

5-Stage Reverse Osmosis System Diagram

Here is our 5-stage reverse osmosis system diagram. It shows an under sink reverse osmosis water filtration system with 3 pre-filter stages, the RO membrane, a carbon polishing filter, a storage tank, and the RO water faucet.

5-stage reverse osmosis system diagram

Filters Used in a 5-Stage Reverse Osmosis System

There are many filter configurations that can be used in a 5-stage reverse osmosis system.

  • You could use 3 pre-filters (2x sediment + 1x carbon), the RO membrane, and a carbon post-filter.
  • Or 3 pre-filters (1x sediment + 2x carbon), RO membrane, carbon post-filter.
  • Or 2 pre-filters (1x sediment + 1x carbon), RO membrane, carbon post-filter, remineralization filter
  • Or 2 pre-filters (1x sediment + 1x carbon), RO membrane, carbon post-filter, UV lamp


Pre-filters are necessary to remove various contaminants from water before they reach the reverse osmosis membrane. Without these filters, the RO membrane would likely get clogged very fast and might not even operate properly. Typical configurations include two sediment filters and one carbon filter, or one sediment filter and two carbon filters.

Ideally, the appropriate combination is determined by analyzing the water quality and the amounts of different contaminants.

Reverse Osmosis Membrane

The reverse osmosis membrane is the main component of the system and it’s what does most of the work. This filter can remove most types of contaminants very effectively, but it’s also affected by the presence of solids and chlorine in the water, requiring that they are removed beforehand.

Carbon Post-Filter

Finally, a carbon post-filter takes care of the finishing touches, like improving the smell and taste of the purified water after being stored in the tank.

Optional: Remineralization/UV Filter

One major downside to reverse osmosis is that it strips water of all minerals that it naturally contains. This could be a problem for people who are used to obtaining their minerals from their daily water intake. One way to address that problem is by adding a remineralization filter which reintroduces those minerals to the water.

A UV light stage can be used to eliminate microorganisms.

Reverse Osmosis System Components

Here is a brief rundown of all the components found in the typical reverse osmosis system.

Main Module

The whole system is packed into one main module, which contains all components, along with connections and threads for hooking up the system.


Pre-filters remove various contaminants before water makes its way to the reverse osmosis membrane, ensuring that the RO system can operate optimally and without any obstructions.

Reverse Osmosis Membrane

The main component of a reverse osmosis system, the membrane, is lined with very fine pores which only allow water molecules to pass through. This is where most of the purification happens.


Post-filters finish the job by eliminating leftover contaminants or enriching the purified water with minerals.

Storage Tank

Since reverse osmosis works so slowly, a storage tank is often used as a buffer to ensure that you always have access to fresh drinking water without having to wait.


Many reverse osmosis systems hook up to their own dedicated faucet for dispensing purified water at a specific point of access.

Drain Line

This line is used to get rid of the wastewater produced in the process.

Feed Water Valve

The feed water valve connects the reverse osmosis system to your water supply.

Automatic Shutoff Valve

With the help of an automatic shutoff valve (ASO), your system never has to work excessively when there’s already enough purified water available.

Check Valve

A check valve ensures that water can never flow back into the reverse osmosis membrane after having passed through it once.

Flow Restrictor

You need a flow restrictor to ensure that the system maintains a sufficiently high level of pressure by preventing wastewater from running through the drain line too fast.

Tubing & Fittings

Finally, you have various tubing sections and fittings that are used to hook everything up together.

Under Sink Reverse Osmosis System

How Does a Reverse Osmosis System Work?

The basic principle of operation of a reverse osmosis system is very simple. The membrane, which we described above, is at the core of the system’s operation. This membrane is lined with very fine pores, which are so small that only water molecules can pass through them. When water is pushed through that membrane at a high pressure, all contaminants get left behind. This is a very effective method for purifying water, which leaves you with almost perfectly pure, clean drinking water.

If you have any questions about our 5-stage RO system diagram please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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