The Parts of a Reverse Osmosis System (with Pictures)

Parts of a Reverse Osmosis System 2

The reverse osmosis system, like many other revolutionary inventions, has been designed through careful study of one of nature’s incredible purifying systems. Saltwater is turned into freshwater simply by passing through a natural membrane-like wall in the earth.

The reverse osmosis system uses this principle to turn polluted and toxic water into fresh, clean drinking water without any bad tastes or smells. But what parts are involved in this simple yet effective process? There is more required than what’s found in the earth to purify water, but it uses the same process and takes seconds to produce pure water. These are the parts.

The Parts of an RO System:

1. Inlet Valve

First, an inlet valve is positioned between the main water supply and the reverse osmosis system to let liquid into the system via the supply lines. It’s where the first phase of the reverse osmosis process takes place in supplying the dirty water. It’s a simple but crucial element of the system. The valve is linked to the main water tank and lets in water only when water transfers out of the tank.

2. Backflow Prevention Valve

The delicate inlet valve is designed specifically with a focus on letting the water in at the right time. Because the system is pressurized, if it was the only valve before the water entering the system, it could be damaged by the backflow, which could break the valve and reduce the system pressure.

Therefore, it has a separate valve that solely lets water out to prevent backflow from the pressurized system. This is called the check valve, and it ensures water can flow freely into the system, but not backward from the system.

3. Pre-Filter

Once the water travels through the first two valves, or sometimes between the valves, it passes through the first initial filter in the reverse osmosis system.

This pre-filter stage of the system comes in a range of different styles, but its main purpose is to eliminate large contaminants like sand and grit from the liquid before continuing through the filter sequence. This ensures the water has no large particles in it before it reaches the main membrane filter.

4. Reverse Osmosis Membrane

Once the water has had the obvious contaminants like sand and dirt removed, it continues on into the main filter called the reverse osmosis membrane. This membrane does the primary work of eliminating everything that makes water unsafe to drink.

The pre-filter will make the water look clean to the naked eye, but it requires a more in-depth filtering system to remove any microscopic contaminants, along with liquid pollutants.

There are different reverse osmosis membranes used for different systems. Some remove all the harmful substances, including chlorine, and others keep the chlorine in the water and remove everything else. Both systems clean the water thoroughly so it’s safe to drink.

5. Drain

All the impurities picked up through this membrane are then flushed out of a drain line connected to a waste pipe. It’s an open line that cleans water that would ordinarily escape without a preventative.

6. Flow Restrictor and Pump

There is a flow restrictor at the drain line immediately after the membrane, so excess water doesn’t get wasted due to a lack of resistance forcing the pressurized system to discharge water.

Depending on the inlet pressure from the water supply, the system also requires a flow restrictor or a flow pump to keep the pressure at the correct level and ensure it runs smoothly. Minimal water pressure means there won’t be much pressure in the tank, and subsequently, water won’t come out of the faucet. Too much water pressure can affect the purity of the water.

7. Storage Tank

The water is now clean and is sent into a tank that holds it pressurized until the faucet is opened. The tank has two bladders inside it that pressurize the water, enabling it to enter and exit when needed. There is always pressure in the tank, and water fills it only until it’s about two-thirds of the water inlet pressure.

At the bottom of the tank, there is a bladder filled with pressurized air, and at the top, there is a butyl water bladder, a thick material similar to the inside lining of a steel food can. When the faucet is opened, the air pressure forces the water out, giving you a steady stream. At the same time, the inlet valve opens to let more water in, which keeps a continuous amount of pressure forcing the water out.

8. Final Filter

At this stage, the water is safe to drink and could immediately continue out of the tank into your cup, but sometimes the liquid is left with an unpleasant taste or smell. You could drink it safely, but the experience may not be so good. So the water passes through one last filter, which gives the liquid a final purifying, so it comes out like fresh water from a stream.

This is a carbon filter that extracts any remaining taste and odor residue that’s left over in the water, and it ensures the natural taste and smell of the water is restored.

9. Faucet

At the end of the line is the faucet, where you or a machine has direct control over the water feed. Turning a single tap handle activates the entire system and brings fresh, clean water out of the tap from any supply of water, no matter how dirty it is.


While there are a few different parts involved to make reverse osmosis systems work, for how effective they are, it’s surprising how little is required. The range of these systems varies between domestic, commercial, and industrial versions, with more or fewer filters and valves depending on their extent. However, they all include the same basic parts to achieve the required process.

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