Mixed water treatment media in automatic filters is a common practice. Most mixed media beds can solve multiple water issues such as turbidity, sediment and iron removal. The Terminator series of iron removal systems we carry make use of a mixed media bed to filter out oxidized iron and can even balance low pH.
Water softener resin can also be mixed. The standard cation water softener resin beads are designed to remove hardness, but there are also anion resin beads that can remove tannins (rotted vegetation particles) from your water. The cation hardness media and the anion tannin media work together quite well. But mixing filter media with ion exchange media does not work out so well.
It is not as common of a practice lately, but not so long ago, there were water treatment dealers adding activated carbon to their ion exchange softener media. The reasons they would do this include removing chlorine for “city water” softeners, improving the taste of the water and also to claim that their “specialty media blend” justifies a higher asking price for the system as a whole. This mixed media truly does improve the water’s quality a great deal – at first.
The problem with mixing activated carbon with softener media is that it will quit working in a very short time. For example, softener media often lasts 10 years or more before it begins to lose efficiency, whereas activated carbon generally speaking, is good for about 2 years. A whole-house auto-backwashing carbon filter system which is sized properly for a family of four in a 1.5 cu/ft tank, treating 2.0ppm (Parts Per Million) of chlorine will be effective for around 2 years. If you were to put 1.5 cu/ft of carbon media into a water softener along with the water softener media, you would need a very large tank. Because the larger tanks require more flow rate to backwash properly, the softener media nor the carbon media will be properly backwashed. That is why most of these multi-media systems include a very small amount of activated carbon media. If 1.5 cu/ft of activated carbon would have lasted about 2 years for you, you can just imagine how long 20% of that would last. So the water treatment company ends up changing out the media every 6 to 12 months at great expense to the homeowner.
There are also some other problems with adding carbon to softeners. The softener media beads are very small and smooth. Hardness ions adhere to these beads and are released when regenerated with a brine solution (salt saturated water). Activated carbon media is coarse and hard. It will abrade the softener media beads over time, pitting them and making it very difficult for the brine solution to release the calcium from the beads.
Most of us have probably seen pictures of the softener systems out there with chambers inside the media tank which divide the carbon media from the softener media. This is a good idea and will allow for both the carbon and softener media to have a longer effective lifespan. But there is a problem with this method as well. While both media are physically separated, they are both subject to the same regeneration process. They are both exposed to the brine water during regeneration. The brine – while rinsed away at the end of the regeneration cycle – adheres quite well to the carbon media particles making them much less effective.
The best way to treat your water for hardness and chlorine is to use two different systems. While this is initially more expensive, it saves you money in the long run, not to mention that both the softener and carbon media will be much more effective and longer lasting.