Perhaps given the concerns about aging water infrastructure or reports about chemicals in public drinking water, you’re considering a reverse osmosis (RO) system. RO systems can certainly remove lead and many other water contaminants, but there are few things you need to consider to optimize efficiency and ensure water safety.
To begin with, how well an RO system will work is highly dependent on the quality of the
membrane itself. Check the manufacturer’s specifications and compare that with your water analysis to ensure the membrane can handle the contaminant load of your particular water supply. For instance, not all RO membranes are rated for lead reduction. Hardness minerals that occur naturally and are very common in waters across the US and Canada can be challenging for RO membranes. Hardness will cause the membrane to readily wear out, requiring more frequent replacements, which will could become expensive very quickly. If your water is hard, you may need to look at installing a water softener before installing an RO system.
Secondly, the integrity of your RO membrane is protected by placing a sediment filter before it. This pre-filtration is one of the “stages” typically built into RO systems. To get the optimum efficiency from your RO membrane, it will be necessary to regularly replace the filter cartridge. Then, following the RO membrane, there will usually be a carbon filter. This is necessary to remove things like chlorine (if you are on municipal water) and volatile organic compounds not removed by the RO membrane.
Now, what about bacteria?
Generally speaking, you should NOT rely on RO membranes to remove microbial contaminants, with the exception of protozoan cysts, like Cryptosporidium and Giardia. These are larger microbes and will be blocked by the RO membrane. That being said, there is still the risk of break-through contamination if there is bacterial growth on your membrane and the membrane gets damaged. Many RO systems will also include an ultraviolet (UV) disinfection system as the final stage of water treatment. UV addresses harmful bacteria and viruses not removed by the RO membrane which can be found in tap water, whether the water source is a private well or municipal water.
RO systems are typically point-of-use and installed at one tap only, and a well-maintained RO system can certainly remove many contaminants from your family’s drinking water. You will likely notice a “flat” taste to the water, though, because the RO also removes naturally-occurring minerals. This taste and the lack of minerals are objectionable to some.
You should also consider the impact your water contaminants could have at the other taps in your home. How much exposure might there be in water that is used for bathing and tooth-brushing, for example? RO systems are not practical for whole-home applications, so may not be the best choice if you’re looking for protection at every tap.
Another key consideration, especially as the stress on water sources increases around the world, is water wastage. While RO systems are getting better in this area, many systems still produce as much as 3-4 gallons of “reject” water for every gallon of potable water produced. That’s a lot of potential water waste, and needs to be taken into consideration, especially in areas experiencing drought.
Like all water treatment systems, there are pros and cons to reverse osmosis. Get to know your water quality and be specific about your concerns to determine an RO system is right for you.