Three Types of Activated Carbon Water Filter

Activated Carbon Water Filters
Then we come to the three types of carbon filters:  carbon-wrapped/impregnated, granulated carbon and carbon block.  All three will improve taste and remove chlorine, but they do have important differences in how well they do it and what else they do.

These are generally used in drinking water systems and sometimes as part of a watermaker fresh water flush system (to remove chlorine if you use bleach in your water tanks).

Carbon wrapped filter
Carbon wrapped or impregnated. These are generally the cheapest of the carbon filters.  They are also the type of carbon filter that is easiest to find.  If you are simply seeking to improve the taste of your water, most will work fine.

However, it’s important to note that they REDUCE the chlorine in the water, they do not totally eliminate it.  Do not use these in any application — such as the freshwater flush system of a watermaker — where total removal of chlorine is needed.  Any amount of chlorine will damage a watermaker membrane.

Generally, these are polyspun or, less often, pleated filters that have a covering of carbon.  Most often, they are offer filtration levels of 2 to 20 microns.  I’ve never seen one that is fine enough to remove bacteria or other microorganisms.  If you just want something that will remove most dirt and chlorine from your drinking water, these will work.  They typically cost just under $10.

Granulated charcoal filter
Granulated Charcoal. The big thing to know about granulated charcoal filters is that they do little to filter sediment from the water.  Further, they do not come in fine enough filtering to remove giardia.  They are easy to identify as they have a solid plastic outer casing.

Granulated charcoal filters are reasonably good at removing chlorine, volatile organic compunds, pesticides and many other man-made substances. They typically come in 2 to 20 micron filtration levels.

The best use for granulated charcoal filters is simply to remove bad taste from drinking water.  Like the charcoal wrapped filters, they do not sufficiently remove chlorine to use on a freshwater flush system with a watermaker if you use bleach in your tanks (or if you alternate watermaker water with city water that could contain chlorine).
Carbon block filter
Carbon block filters. The most all-encompassing filters are carbon block filters, but that doesn’t mean that just any carbon block filter will do.

Only the finest 0.5 micron carbon block filters will remove giardia and cryptosporidium, both of which can cause severe diarrhea.  The 0.5 micron carbon block filter is also virtually 100% effective in removing chlorine, and is what most watermaker manufacturers recommend on their freshwater flush systems to ensure that no chlorine reaches the membrane.
A carbon block filter’s effectiveness at removing sediment is dependent upon the micron rating of the filter, although water with visible dirt and sediment will quickly foul the highest quality carbon block filters.  Carbon block filters can remove small quantities of heavy metals, but they can’t cope with high concentrations and shouldn’t be relied upon for that.

Carbon block filters can be made from any of several materials; coconut shell carbon is the best, but also costs a little more.