Reverse Osmosis Water System

A simple description of how a reverse osmosis system works would be as follows. The process of osmosis is simply the passage of a solvent through a semi-permeable membrane from one side of the membrane that has a low concentration of a solution to the other side with a higher concentration of the solution. Reverse osmosis does as the name implies; it reverses the direction of flow during osmosis.

So, in a water system it will force the solvent (water) to pass from the higher concentration of the solution to the lower solution concentration side of the membrane; which is relatively simply achieved by applying an external pressure to the solution on the higher concentration side of the membrane.

Why is Reverse Osmosis Needed?

Unless you live in an a area that gives you a very pure and ‘soft’ water supply, either naturally or through a water utility company, your water will contain all manner of dissolved and even suspended particles, which are typically minerals and salts.

Some areas are renowned for having excessive amounts of these minerals and salts in their water, resulting in hard water that can taste unpleasant, leave a residue on washing and create lime-scale in water pipes - people living in these areas may well need a reverse osmosis water system to clean up their water.

What a Reverse Osmosis Water System Does

Whilst the main unit in a reverse osmosis water system moves the water from a high concentration of dissolved particles through a membrane to a lower concentration of the solution, thereby removing most of the dissolved particles, it also has a system of tanks and filters to remove solid and suspended particles.

Some of these particles can be removed by being allowed to settle out into sedimentation tanks, whilst others will be removed by passing through what are often carbon filters, before the water is passed through the membrane for its final cleaning. At the end of the process water that started out as being ‘hard’ or contaminated water will be around 98% purified, which without distilling it is probably as close to pure water as you can get.


Probably most significant advantage of having a domestic reverse osmosis water system to purify all of the water you use is that you will only require one unit to be fitted in your home, which is typically located as close to where the water supply enters your property as possible.

The alternative is to have reverse osmosis units fitted to every faucet or water outlet valve in your home, in other words, however many sinks, bathtubs, shower units, dishwashers, washtubs, ice makers etc that you have.

Also, if you only want to be able to obtain pure water for drinking from your kitchen faucet - then just fitting one faucet unit would make sense. But, if you want to not only have clean and pure water throughout your home, but also to protect your water pipes and heating units from lime-scale, then you really need a unit that will clean up the water to all of your water usage points.

Reverse osmosis water systems can be very low maintenance. Whilst the carbon filters will need replacing from time to time the sediment tanks and even the membrane itself can be self cleaning, sending the waste matter directly to your outdoor drain.

See Also: No Salt Water Softeners