by Steve Marshall

Created on: July 21, 2008   Last Updated: July 22, 2008

One of the best water filtering systems around, is a reverse osmosis water filter system. It is simple, easy to run, and doesn't have the added heating costs associated with boiling water, as in the distillation process. It is quiet, except for the pleasant sound of running water.

Purification of the water is nearly as good as that achieved by distillation, because of the way the water is filtered. In a reverse osmosis water system, water is forced under pressure through a semi permeable membrane. The membrane is a very fine filtering device, so fine, and microscopic, that it allows essentially, only water molecules to pass through its surface. Larger particles, and contaminants cannot go through the membrane, being too large to fit through its tiny pores.

When water is forced through the membrane, it allows the small molecules of water to pass through, producing purified water. Impurities are left on the other side of the membrane.

The quality of this water filter, depends on the membrane's quality. It must be maintained, and periodically cleaned, as the membrane clogs up with usage. Some systems have inbuilt flushing devices to achieve this cleaning. The membrane should be inspected regularly. If it starts to deteriorate, and develops a crack, or a small hole in it, water quality will be compromised, and deteriorate rapidly. If the membrane freezes, cracks can easily develop in it.

Some membranes carry an electrical charge to further repel certain chemicals, at the surface of the membrane. The reverse osmosis method creates some waste water, that can be flushed down the sink, or captured, and used on garden beds. The waste water contains contaminants, but they are not concentrated enough to damage plants.

Different materials such as cellulose acetates, or other types of polyamide resins, are usually selected for the membrane.

Reverse osmosis drinking water systems for the home can be conveniently plumbed into your normal water supply system, and hidden neatly under your sink. Stand alone units, placed on top of the sink, connecting directly to your tap, through a hose like connection, are also available.

Reverse osmosis water filter systems have been utilised for many years by ships, and aircraft carriers, to create pure water from seawater, and are an improvement over older methods of carrying fresh water.

Reverse osmosis, produces high quality drinking water, and effectively removes contaminants. Heavy metals, cadmium, mercury and lead, and inorganic salts, such as lime and nitrates, bacteria, and microorganisms, including cysts cannot pass through the membrane.

In nature, osmosis is the process plants use to absorb water from the soil. The outer structure of the plant wall, acts as a membrane, during which a type of internal pressure is created, known as osmotic pressure. This process is reversed when pressure from a water tap, forces water through a reverse osmosis membrane. This process is called reverse osmosis.

An activated carbon filter is usually added, to further treat the water, and to remove organic chemicals from the water, such as chlorine. This improves the water's taste. Carbon filters are important, because chlorine passing through your osmosis membrane will shorten its life.

Better systems have pre, and post carbon filters, and a larger particle type pre filter. This filter removes dirt, sand, rust, and other sediment type particles. These clog up a reverse osmosis membrane, if not prevented from entering the system, and damaging the sensitive reverse osmosis membrane.

Reverse osmosis systems, are one of the better systems of creating pure drinking water. For me, I still prefer steam distillation methods, and which remain the mother of all water purification systems.

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