There are two caravan filters we do, a single and a twin. The advantage of the twin over the single is that it has a dedicated 1 micron sediment filter in the first stage to remove many of the physical contaminants present in rural water supplies. This can greatly increase the usable life of the carbon filter which would otherwise become blocked with sediments before it had achieved its maximum life.
Our systems use industry standard cartridges so you are always able to source a replacement cartridge of some description in an emergency. We are only ever a phone call away anyway, but just another advantage.
The carbon filter I would recommend is our Multipure Premium filter which is classed as a water purifier rather than just a filter due to its 0.45 micron rating that ensures removal of Giardia and Cryptosporidium cysts. It also has high heavy metal and other contaminant removal properties that may be useful in certain water supply areas. It is also able to be used in areas that use Chloramine disinfection (e.g. Kalgoorlie, Broome, Eastern States) as opposed to the normal chlorine used in Perth water supply. Most other standard carbon filter cartridges are not able to remove chloramine.
Other caravan filter cartridges I have seen at the caravan & camping shows use silver as a disinfectant in the cartridge but most of these are above 1 micron, which means they don’t guard against bacterial cysts and don’t have the heavy metal capability. The levels of residual available silver in the water are dependent on many chemical factors in the supply water and are notoriously short lived as opposed to the projected life of the cartridge. I personally feel it is better to remove the problem in the first place than to try and deal with it in the storage tank. The greater the level of organic and mineral sediments getting to your tank, the greater the nutrient levels available for algal and bacterial growth.