There are many different types of water filter systems on the market, appealing to different budgets and performance expectations. Also, the quality of the water coming to your home can vary greatly, with some systems offering very clean water, but others including rust, dirt, bacteria and other unsavory substances. At the top of the line in terms of cleanliness is the reverse osmosis water filter system.
Reverse osmosis, or RO, was originally quite an expensive process used mainly in military vessels back after World War II to desalinate seawater for drinking. Over the next couple of decades private manufacturers began to produce systems for home and commercial use, although they were rather expensive. In more recent years, the technology has been refined further, and costs have come down to more-affordable levels (although it is still noticeably more expensive than conventionally filtered water in most cases).
How does it work? The basic concept is not unlike using a filter, although there are some very important differences. The water passes through the membrane material, allowing the water molecules and a few other small molecules to pass, but leaving behind the vast majority of other substances. A filter has small holes in it of course; a Reverse Osmosis water filter membrane has vastly smaller holes-pores really that are thousands of times smaller than what is in a typical filter-and the water won't really go through it unless it is forced under pressure. So there is higher water pressure on one side of the membrane and lower pressure on the other side, thus pushing the water past. For this reason the much of the important stuff happens inside a pressurized container, so you don't want to be buying cheap materials.
It is not uncommon to include one or more cartridge filters upstream of the reverse osmosis water filter system to remove the larger contaminants; this helps the more-expensive membrane to last longer. Some RO systems have the ability to clean the membrane off, thus extending its life without maintenance effort. However, eventually the membrane and filter elements must be removed, so part of the research process should include understanding how long these will last; what is the capacity in terms of gallons or months?
You might spend 20 cents per gallon for water from a reverse osmosis water filter, so it does not make sense to use it for things other than drinking and cooking. However, RO will remove over 99% of most substances including dirt and rust of course, but also stuff like copper sulfate and the pesticide DDT. There are other substances like lead, mercury, chlorine, bacteria and viruses that are cleaned to a good 95% removal level or so.
As noted above, it would probably be a mistake to purchase a cheap system trying to save money. If it is less than around $200 to $250 it is likely of inferior quality, unless that price represents a big discount from the regular price. Over time cheaper
systems will experience leakage in the membrane and pressure container. It may be necessary to replace the filters and membrane more often as well.
The purchase of
affordable reverse osmosis systems is an important step, and worth some time on research. It is worthwhile to compare the features between the two or three most-likely candidates, and perhaps even a phone conversation with a representative to ensure you have what you need to know to make a wise choice.
