Remineralizing Reverse Osmosis Systems
If you're been researching the purchase of a reverse osmosis system for your home, you've likely encountered the terms Remineralized Water & Alkaline Water. Speaking from a strict chemistry perspective, these terms are often misused and misunderstood and the confusion they create can be frustrating for homeowners who just want to figure out which RO system to buy.
Remineralized Water is water that has had some mineral content added back to it. The reverse osmosis process is non-selective - it removes the 'good' stuff like calcium, and magnesium, along with the 'bad' stuff like pesticides, heavy metals, and pharmaceuticals. The process of remineralizing the water adds back some of the good stuff. This is usually done with a post-filter that contains some form of calcium or magnesium. The most common substances used are Calcite (calcium carbonate) and Corosex (a magnesium compound). Some filters use a combination of both. The reverse osmosis treated water is passed through one of these filters where it dissolves some of the filtration media immediately before being dispensed. Calcite remineralizers will bring the pH to neutral (about 7.0) while Corosex will bring the pH above 7. Any liquid with a pH greater than 7 is referred to as a 'base' although the term alkaline has replaced this word in popular discussions.
Alkaline Water is a term that needs some explanation as it is often interchanged in popular media with the term basic. In the strict scientific definition, any solution that has a pH greater than 7 is basic. Alkalinity is the acid-nuetralizing capability of a solution. A solution with a basic pH and low alkalinity can have the pH altered with only a small amount of acid added. A solution with basic pH and high alkalinity can absorb a higher amount of acidic material before the pH of the solution will drift downwards.
The health effects of drinking basic pH water and/or alkaline water are not firmly established in the scientific community. What has been established is that some people find reverse osmosis water that has been remineralized to be tastier. If you want to know how remineralized vs. non-remineralized RO water tastes, have a sip of Dasani water and then have a sip of Aquafina. Both are produced through the RO process. Dasani has some mineral content added back in and Aquafina does not. If you'd like to remineralize your own RO water, here's a breakdown of how to do it:
If you don't yet have an RO system, you'll want to find one that has easy access to the carbon post filter like these ones do:
Then, you have a choice of a bunch of different filter cartridges that can be swapped out for the standard inline carbon filter. Here are a few options:
Calcite + Carbon:
Calcite + Corosex:
When you're selecting a filter cartridge, make sure that you choose one that has the correct ends. Some cartridges have threaded female connectors while others have push-to-connect fittings that will receive a plastic tube.