How It Works

What Is Reverse Osmosis?

Reverse osmosis water filtration is the best water purification method available aside from distillation. Most commonly used by premium bottled water companies, it is effective in eliminating or substantially reducing a wide range of contaminants.  Of all methods used to treat residential drinking water, reverse osmosis has the greatest range of contaminant removal as it will remove particles as small as individual ions. The pores in a reverse osmosis membrane are approximately 0.0005 micron in size.  When compared to the size of bacteria at 0.2 to 1 micron & viruses at 0.02 to 0.4 microns, you can see the reverse osmosis is highly effective at purifying both municipal and well water.

There are two types of RO membranes commonly used in home water filtration systems: Thin Film Composite (TFC) and Cellulose Triacetate (CTA). TFC membranes will filter out more contaminate so are said to have a considerably higher than a CTA membrane. However, they are more susceptible to degradation by chlorine. This is one of the reasons why it is imperative that you reverse osmosis system includes a set of pre-filters with an activated carbon stage, especially if you have municipal water.

How Does Reverse Osmosis Water Filtration Work?

The reverse osmosis membrane is semi-permeable which allows pure water to pass through while capturing the contaminants too large to fit through the membrane’s pores. The best reverse osmosis systems utilize cross-flow which allows for continuous cleaning of the membrane to prevent premature fouling.  What this means is that some water passes through the membrane, the rejected water (brine) continues downstream, clearing the contaminants past the membrane and down the drain. The reverse osmosis process requires a decent amount of pressure to push the water through the membrane , a minimum of 40psi, which is standard for a residential water system.

Will A Reverse Osmosis System Work For Me?

Reverse osmosis is the best choice for nearly all home water purification needs. It is a highly recommended solution for homes utilizing pre-treated municipal water.

While reverse osmosis is very effective at removing bacteria and viruses, it cannot be the only level of purification for water that is known to contain or may contain biological contaminants (untreated well or lake water, for instance). For those situations, the addition of an ultraviolet light stage to the system is deadly effective against bacteria and viruses.

RO membranes are subject to degradation by chlorine, iron, manganese, and hydrogen sulfide, and to bacterial attack, a sediment pre-filter and an activated carbon pre-filter and post-filter should used in your reverse osmosis system. Water softeners used in advance of an RO system can be necessary with excessively hard water to prevent pre-filter and membrane fouling. RO systems are also ideal for water contaminated with high nitrite levels, common in agricultural areas.

What Contaminates Does Reverse Osmosis Remove?

Nominal Rejection Characteristics of Thin Film Composite Reverse Osmosis Membranes

Pros and Cons of Reverse Osmosis Systems

Advantages:

• Very high rejection rate for a wide array of contaminants
• Very cost effective in the long term, costing as little as 5 cents per gallon of pure water once maintenance and water costs are factored in
• Eliminates water bottle waste

Disadvantages:

• Requires sediment and carbon pre-filtration (included as part of our systems) to prevent membrane fouling
• Produces 3-6 gallons of waste water for each gallon of pure water, however, waste water can be re-captured for use in toilets.  Waste water can be reduced by up to 80% with the use of a permeate pump (included on our systems)