How Does Reverse Osmosis Work?

Reverse osmosis systems purify water by forcing pressurized water through a very fine, plastic membrane. If the raw water being treated comes from a well or another private source, disinfection and pre-filters (to remove chlorine and/or particulates/sediment) may be needed in advance of the R/O unit to remove contaminants that can foul or damage the membrane.

Stages of reverse osmosis:

1. During the initial filtration stage, tap water or well water (pressurized by a booster pump) is passed through a particle filter (a pre-filter) that removes silt, sediment, sand, and clay particles that might clog the R/O membrane.
2. The water is then forced through an activated carbon filter that traps minerals and contaminants such as chromium, mercury, copper, chloramine and pesticides. It also removes chlorine, which is important, as chlorine will shorten the life of the membrane.
3. Water is transferred under pressure into the R/O module, allowing only clean water to pass through the small pores in the membrane. Impurities unable to pass through the membrane are left behind and flushed down the drain.
4. Treated water is then sent to a storage-tank.
5. Treated water is passed through an activated carbon filter before use to further improve the water's taste and smell.

Water that contains manganese, hydrogen sulphide or iron should be pre-treated to extend the life of the membrane. A dealer can recommend the pre-treatment needed.

Note: Reverse Osmosis units produce no noise other than the sound of water discharging into the drain (usually a sink or a floor drain).

How Do I Know What Size Unit to Buy?

R/O units are rated according to the amount of treated water produced per day. For example, one type of unit produces 50 litres of treated water per day under its design conditions. Such a unit is generally rated with 60 psi water line pressure, a water temperature of 25° C (77° F), normal dissolved solids and 2 atmospheres of pressure. In reality, conditions frequently vary. Line pressure is often lower, water will frequently be colder than 25° C and backpressure in the storage tank will likely reduce the performance of the unit. Consequently, you should examine water conditions and buy a larger rated unit than needed if any of the above problems are noted.

What Are the Benefits of Reverse Osmosis?

Reverse osmosis can remove dissolved solids, salts, minerals that cause hardness, organic chemicals and other impurities. It can improve the taste of water for people who do not like the taste of dissolved mineral solids.

Treated water will not produce scale in kettles and coffee makers. Because sodium and potassium are removed, people on a medically prescribed sodium- or potassium-restricted diet may benefit. R/O units may also remove contaminants such as chromium, mercury and nitrates.