Reverse Osmosis and How it works

What does a Reverse Osmosis Filter System (ROFS) do?

A ROFS produces drinking water from your tap, Reverse Osmosis is a simple and straightforward water filtration process. It is the most common system used for water bottling plants, and has been used for years to desalinate water (convert sea water to drinking water). With the many options in the water filtration market place, it can be confusing to understand the different methods. The goal here is that as you read on you can gain a better understanding of RO.

The important points to consider:

  • All RO systems work under the same principles.
  • The only difference is the quality of filters and membranes used in designing the system.

How does a Reverse Osmosis Membrane work?

The Reverse Osmosis membrane has a tight pore structure (less than 0.0001 micron or 500,000 times less than the diameter of a human hair) that removes all the contaminants of concern to the consumer including bacteria, viruses, parasites, heavy metals, inorganic chemicals, pesticides and algae from drinking water. Additional Carbon filters used in Reverse Osmosis also help to remove unwanted odors, colors and tastes from water.

Factors that affect performance:

  • Incoming water pressure.
  • Water temperature.
  • Type and number of total dissolved solids (TDS) in the tap water.
  • The quality of the filters and membranes used in the RO system.

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What are the advantages of RO?

  • Improves taste, odor and appearance (coffees and teas).
  • Removes the pollutants listed below and more!
  • Does not consume energy.
  • Does not collect pollutants but flushes them down the drain.
  • Easy to keep clean.
  • Low production cost – bottled water quality for pennies from your tap.

What does it Remove

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Basic components common to all Reverse Osmosis Systems:

  1. COLD WATER LINE VALVE: valve that fits onto the cold water supply line. The valve has a tube that attaches to the inlet side of the RO pre-filter. This is the water source for the RO system.
  2. PRE-FILTER SEDIMENT FILTER: water from the cold water supply line enters the Reverse Osmosis pre-filter first. The most commonly used pre-filters are sediment filters. These are used to remove sand silt, dirt and other sediment.
  3. PRE-FILTER CARBON FILTER: used to remove chlorine, and other unwanted taste and smells from the water.
  4. REVERSE OSMOSIS MEMBRANE: the water is then filtered through the RO membrane.
  5. POST-FILTER CARBON: to polish the water before drinking, a carbon filter is added. This will help ensure great quality water.
  6. AUTOMATIC SHUT OFF VALVE (SOV): the automatic shut-off valve will help to conserve water. When the storage tank is full this valve will prevent any additional water from entering preventing any more water from being filtered. By shutting off the flow this valve also stops water from flowing to the drain. Once water is drawn from the RO drinking water faucet, the pressure in the tank drops and the shut off valves opens, allowing water to flow to the membrane and waste-water (water containing contaminants) to flow down the drain.
  7. FLOW RESTRICTOR: to regulate flow through the RO membrane there is a flow control. Based upon the gallon capacity of the membrane, this device will maintain the flow rate to give you the highest quality drinking water. Without this device it would reduce production capacity as water would take the path of least resistance and flow through the drain line.
  8. STORAGE TANK: the standard RO storage tank holds up to 13 gallons of water. Inside the tank there is a bladder that keeps the system pressurized.
  9. FAUCET: the RO unit utilizes its own faucet next to the sink.
  10. DRAIN LINE: this line runs from the outlet end of the RO membrane housing to the drain. This line is used to dispose of the impurities and contaminants found in the incoming water source (tap water).

Are all Reverse Osmosis Systems and filters the same?

RO systems can appear similar in terms of design and components. However, the quality of those components can be very different. The difference in quality can effect the product water from the system.

Ned Van Allan is the Director of Business Development at Juturna Water and is 1 of 10 Certified Water Professionals in the State of Georgia by the Water Quatlity Association. He is the only Certified Water Specialist in Central Georgia that is still active with the day to day operations. He can be reached at or @ 706-453-1800 to further discuss water, water testing, or how to read a water test. You can visit the website at