What Is Reverse Osmosis (RO) & How Does It Work?

Mehdi Norouzy • February 5, 2026

Reverse Osmosis is a water purification process that uses pressure to force water through an ultra-fine membrane, removing dissolved contaminants that normal filters cannot remove.

๏ปฟ

๐Ÿ‘‰ Think of it as water squeezing through a microscopic sieve.


RO technology is widely used for drinking water purification in homes, offices, laboratories, and even medical facilities, making it one of the most trusted filtration methods available today.

Step-by-step: How an RO system works


1๏ธโƒฃ Tap water enters the system

Water from your main supply flows into the RO unit under normal pressure.


2๏ธโƒฃ Pre-filtration (protects the membrane)

Before reaching the RO membrane, water passes through prefilters:

โ—       Sediment filter → removes sand, rust, dirt

โ—       Carbon filter → removes chlorine & chemicals


๐Ÿ”‘ Purpose:

These filters shield the RO membrane from harm and blockages.

Pre-filtration is especially important in regions with desalinated or hard water, as it helps extend system life and maintain consistent performance.


3๏ธโƒฃ The RO membrane (the heart of the system)

This is where the magic happens.

โ—       Pore size ≈ 0.0001 micron

โ—       Removes:

โ—       Heavy metals (lead, mercury)

โ—       Salts & minerals (TDS)

โ—       Fluoride, arsenic

โ—       PFAS

โ—       Bacteria & viruses


Two streams come out:

โ—       โœ… Permeate → clean drinking water

โ—       โŒ Concentrate (brine) → dirty water flushed to drain

๏ปฟ

This membrane is capable of removing contaminants at a molecular level, delivering water that is significantly purer than standard filtration methods.

reverse osmosis under sink filter system

4๏ธโƒฃ Booster pump (in modern systems)

Modern or tankless RO systems typically come with a pump:

โ—       Increases pressure

โ—       Improves filtration efficiency

โ—       Reduces wastewater

โ—       Higher pressure = lower TDS + better flow.

Booster pumps are particularly beneficial in apartments or areas with low water pressure, ensuring consistent output and faster water production.


5๏ธโƒฃ Post-treatment (polishing the water)

After RO filtration:

โ—       Carbon polishing filter → improves taste

โ—       Mineral filter → adds calcium & magnesium back

โ—       pH balance → brings water to balanced pH level for your body

RO water is very pure – minerals get added to improve health & taste.


6๏ธโƒฃ Optional UV sterilisation

Some systems add UV-LED:

โ—       Kills any remaining bacteria/viruses

โ—       Final safety barrier

โ—       Especially useful in warm climates

UV treatment adds an extra layer of protection, making the water microbiologically safe right before consumption.


7๏ธโƒฃ Water goes to the faucet

Now you get:

โ—       Clean

โ—       Clear

โ—       Neutral-tasting

โ—       Low-TDS drinking water

Tankless systems produce water on demand.

Tank systems store it in a pressure tank.

Choosing between tank and tankless systems depends on space availability, daily water usage, and convenience preferences.


RO Water for Everyday Use


RO-purified water is suitable not only for drinking but also for cooking, making tea or coffee, washing fruits and vegetables, and preparing infant food. Using purified water daily helps reduce exposure to unwanted contaminants and improves overall taste consistency across all household uses.

This makes RO systems a practical long-term solution for households aiming to maintain consistent water quality throughout the year.


NADINE AQUA RO systems combine advanced filtration with a sleek, space-saving design for modern kitchens.

best RO water purifier in Dubai
By Mehdi Norouzy September 9, 2026
Yes, a standard reverse osmosis system removes most minerals along with the contaminants. But that doesn't mean your water ends up empty or unhealthy. At Nadine Aqua
water filtration systems in Dubai
By Mehdi Norouzy September 5, 2026
At Nadine Aqua, we go several steps further. Our British-designed water filters use 11-stage water filtration to strip out dirt, bacteria, heavy metals
best RO water purifier in Dubai
By Mehdi Norouzy September 1, 2026
You live in a clean, well-maintained building. Your unit looks spotless. So why does your water sometimes smell strange or taste different depending on the day