Reverse Osmosis Filters: Exaggerated Claims For & Against Reverse Osmosis Filters

Reverse osmosis filters are one of the most popular home water filtration systems, yet they are also one of the most widely opposed. Their manufacturers claim that reverse osmosis filters are able to stop any and all contaminants. Those who oppose RO filters accuse them of being completely useless, asserting that they are only a nest for bacteria, actually making water more dangerous rather than safer. What is the truth?

As always, the truth is somewhere between those two opinions. RO filters are good, but neither perfect nor universally suitable.

How do reverse osmosis filters work?

In short, the reverse osmosis process relies on pushing water through a membrane that traps the contaminants on one side and forces clean water through to the other. The commonly used membranes have no pores and the water is able to cross it only because of the diffusion process. This treatment is 100% effective against the inorganic contaminants and theoretically should be able to get rid of bacteria as well. However, in practice reverse osmosis filters are known to let some bacteria to pass through, usually through the micro-leaks around the membrane, but also through the membrane itself.

Why some people praise reverse osmosis while others curse it?

Most honest people who praise home water filtration systems that rely solely on RO water filters either simply repeat what the advertisements claim or they are really doing so because reverse osmosis filters are the most cost-effective solution, especially in places where the bacteria aren't the real problem. If you add to that the fact that they are aggressively marketed and the marketing languages don't have such words as “mostly” or “for the most part”, you see why some people say that reverse osmosis is really cool.

On the other hand, those who hate reverse osmosis filters and claim that everyone should avoid home water filtration systems that use only RO filters, are also partially right.

First, the reverse osmosis filtration systems require a lot of careful maintenance in order to keep them working. The membranes have to be checked and replaced on a regular basis or you risk them becoming infested with all kind of bacteria. Keep in mind that RO doesn't kill bacteria, it simply contains them on one side of the membrane.

Also, reverse osmosis filters are known to work at peak performance when the contamination level is relatively low. The more the water is contaminated, the worse performance RO filters have, especially when dealing with bacteria.

The bottom line on RO filters ...

Use reverse osmosis filters whenever you need a reasonable quality for a low price or when a multi-stage home water filtration system is out of question (for example, while travelling). Just make sure the system gets its share of maintenance and remember you can't completely trust a home water filter that rely solely on a reverse osmosis. If you can afford it, buy a multi-stage filter, preferably one that will incorporate both a reverse osmosis filter and some strong UV lamps to kill the bacteria.