Is Reverse Osmosis The Best Water Filter For Your Home?

November 01, 2013 by Andrew Moorey

Typical RO Water Filtration System For The HomeIn my opinion, the answer is generally no. While reverse osmosis, commonly referred to as “RO” is a very powerful technology, it is not the best water filter for most homes or offices. Reverse osmosis is best suited to address the two issues for which it was originally designed:

  1. Desalinating brackish water or sea water and/or
  2. Reducing very specific chemical contaminants.

You might need RO if you are facing challenges with flouride, sodium, total dissolved solids (TDS) or chemicals like arsenic, radium, nitrates and nitrites, etc. If that's the case I recommend taking a look at the Everpure ROM II or ROM III RO systems which you can learn more about here. 

What then is the best water filter for your home or office?

In our opinion, the best technology for home or office applications served by municipal water utilities is a combination of high quality carbon and sub-micron filtration. One of the best examples of this technology that we've found is the Everpure H-300 under-the-sink water filtration system which offers:

  • Simple installation,
  • Dedicated faucet, (take back your fridge!)
  • Minimal maintenance
  • Visual filter change indicator and
  • Reduction of harmful contaminants to NSF/ANSI permissible limits, without removing healthy minerals.

Why reverse osmosis may not be the best water filter for you.

Reverse osmosis has a reputation as being the ultimate in water purification technology. This often stems from its use in military theatre. Military users may be deployed anywhere in the world and need to be prepared to treat a wide variety of challenging water sources including sea water and/or water contaminated with chemical, biological, radiological, and/or even nuclear contaminants. It is important to note however that while these military grade, mobile reverse osmosis water purification units (ROWPU) do include reverse osmosis membranes, they also include a wide variety of other treatment technologies such as ultraviolet light, activated carbon, pre-filters, post filters and very specialized filter media to fill in the gaps that RO itself does not address.

And while reverse osmosis water filters will reduce a pretty wide spectrum of contaminants such as dissolved salts, Lead, Mercury, Calcium, Iron, Asbestos and Cysts, it will not remove some pesticides, solvents and volatile organic chemicals (VOCs) including:

  • Ions and metals such as Chlorine and Radon
  • Organic chemicals such as Benzene, Carbon tetrachloride, Dichlorobenzene, Toluene and Trihalomethanes (THMs)*
  • Pesticides such as 1,2,4-trichlorobenzene, 2,4-D and Atrazine.

*Trihalomethanes are formed as a by-product predominantly when chlorine is used to disinfect water for drinking. They represent one group of chemicals generally referred to as disinfection by-products. They result from the reaction of chlorine or bromine with organic matter present in the water being treated. The THMs produced have been associated through epidemiological studies with some adverse health effects. Many governments set limits on the amount permissible in drinking water. However, trihalomethanes are only one group of many hundreds of possible disinfection by-products—the vast majority of which are not monitored—and it has not yet been clearly demonstrated which of these are the most plausible candidate for causation of these health effects. In the United States, the EPA limits the total concentration of the four chief constituents (chloroform, bromoform, bromodichloromethane, anddibromochloromethane), referred to as total trihalomethanes (TTHM), to 80 parts per billion in treated water. Source: Wikipedia

While reverse osmosis technically provides a mechanical barrier that is more than suitable for the reduction of biological contaminants such as protozoan cysts, bacteria and viruses, it is important to realize that many reverse osmosis membrane manufacturers have not performed testing and/or received certification for these contaminants and generally issue statements such as the following:

Notice: The use of this product in and of itself does not necessarily guarantee the removal of cysts and pathogens from water. Effective cyst and pathogen reduction is dependent on the complete system design and on the operation and maintenance of the system.

For the ultimate in confusion, try and search the web for a definitive listing of what contaminants reverse osmosis can remove or try to compare different residential systems from different manufacturers side by side. So much depends on the system design, maintenance and raw water source that it can be a real challenge to determine the expected performance and protection that a residential reverse osmosis system can offer to you and your family or coworkers.  While reverse osmosis as a technology may be known to have the ability to remove certain contaminants under laboratory settings; a commercial system, especially a residential system, may not have similar capacity. When looking at a residential RO system, read the fine print, product specifications and contaminant reduction claims carefully. When in doubt, look for a system that meets NSF/ANSI Standard 58.

Reverse Osmosis is not the simplest or most cost effective technology.

Most reverse osmosis systems require a constant flow of water to clean and flush their membranes. This water is disposed of as waste water. Between 50-80% of the water entering the water treatment system can be disposed of as waste water, something referred to as concentrate (because the contaminants are concentrated in this stream of water). The amount of water produced by the system for drinking is called the recovery rate (the amount of good water recovered from the original water source). If you receive a water bill each month or quarter like most of us do, you would be paying for all of the water your RO system sends down the drain. Using the GE Model #GXRM10RBL as an example, it has a recovery rate of 18.77% which means that for every gallon of water produced for drinking, approximately 5.5 gallons would go down the drain.

All of the waste water produced by an RO system requires a drain of course, something that often times complicates the installation process of reverse osmosis water filtration systems.

Thorough attention must be paid to maintaining reverse osmosis water filtration systems. RO membranes are subject to degradation and/or deterioration by sediment, chlorine and even bacteriological growth (we all know what happens to an old kitchen sponge). Should you forget to change your carbon pre-filter on schedule, it will no longer have capacity to remove the chlorine from your municipal water supply resulting in a damaged or destroyed RO membrane. And how do you know if your RO membranes have been compromised? With most residential systems, you simply won’t know unless you are able to test the total dissolved solids TDS of your raw and treated water on a regular basis.

Want to see what a typical RO installation looks like along with some of the maintenance requirements? Check out this YouTube video . Fast forward to 13:35 to see if RO operation and troubleshooting is a good fit for you and your family or office. Note the requirement to flush and maintain the RO storage tank where water can go stale if not used regularly, especially if there is no additional disinfection or treatment post tank.

Is demineralized water produced by reverse osmosis or even distillation good for you?

No, it’s actually not. According to the World Health Organization, low (TDS) water produced by reverse osmosis or distillation is not suitable for long term human consumption and in fact, can create negative health affects to those consuming it. This lack of minerals also contributes to the awful taste that reverse osmosis water is known for. Stay tuned for our next blog post which will focus on the negative health effects of demineralized water produced by reverse osmosis and distillation.

What does this all mean?

  1. Reverse osmosis was originally invented as a means of desalinating brackish or seawater sources and should be used as the tool for which it was intended.
  2. Contrary to its reputation, reverse osmosis does not remove 100% of all contaminants and both reduction rates and certifications vary widely depending on the contaminant in question
  3. RO membranes can be damaged and destroyed by the chlorine found in most municipal water supplies and thus require carbon pre-filtration
  4. Reverse osmosis water treatment systems are one of the most complicated types of systems on the market today and require pre-filters, storage tanks, pumps, drain connections and diligent attention to maintenance and testing.
  5. According to the World Health Organization, low TDS or demineralized water produced by reverse osmosis or distillation is not suitable for long term human consumption and in fact, can create negative health affects to those consuming it. Stay tuned – we’ll discuss further in our next blog post "Is Demineralized Water Bad For Your Health?".

Do you have an reverse osmosis systems in your home or office? Have you had one in the past? We'd love to hear about your experience!

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