Recent post on rv.net (web address below)and many other websites give lots of info on many filters and filter systems - as well as coconut carbon and why one is better than another for various reasons. I recently met a couple people using UV and learned they are not that expensive or difficult to install. We use several different filters for different levels of filtration to not only filter our "whole house" but our drinking water. Websites where more can be learned....
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27409656/srt/pa/pging/1/page/1.cfm
http://www.filtersfast.com/P-Hydronix-SMCB-2510-Water-Filter.asp
http://www.purewaterproducts.com/articles/carbon
There are many types of carbon. Most filter carbon is manufactured from coal, but other substances like wood and nut shells are also used. Coconut shell carbon is becoming popular not only because it is made from a renewable resource but also because it produces very good tasting water and is particularly good at trihalomethane removal. A new specialty carbon called catalytic carbon is now available that will remove hydrogen sulfide gas (which produces the "rotten egg" smell in some well water) and is very good at removing chloramines (the mixture of ammonia and chlorine used as a disinfectant by some water supplies).
http://www.ebay.com/bhp/10-carbon-water-filter
http://www.amazon.com/Hydronix-BLUE-Carbon-Block-Filter/dp/B008B7ZB1C
http://www.uswatersystems.com/residential/hydronix-carbon-block-filter-2-5-x-10-5-micron-cartridge.html
http://www.thewaterpage.com/active-carbon-block.htm
Activate carbon water filters are rated by the size of contaminants they remove. These range from around 50 microns down to .5 microns. The smaller the measurement the more effective the filter. A number of different substances are used to make the carbon for these filters, such as bituminous, wood and coconut shell. Of these, coconut shell is the most expensive, but has been found to also be the most effective. It has the ability to remove even the smallest particles of contaminant.
http://www.waterfilteruniversity.com
http://www.h2osplashwaterfilters.com