If you are concerned about giardia, cryptosporidium, coliforms, and other biological pathogens in your water, you have several methods of protecting yourself. One of these is to render the microbes harmless with a UV system, one of the most effective choices for preventing water-borne illnesses.

Why UV?
Ultraviolet light can be dangerous to humans, and it is positively lethal to microorganisms. When exposed to UV light, many of them  will die, but virtually all of them will be rendered sterile and unable to reproduce. Without reproducing inside your body, they can't make you sick. UV is particularly effective with viruses, as they are very difficult to remove from your water by filtration. Some viruses have even passed through reverse osmosis systems, although it is rare. So, to protect yourself from viral infection from your water, your best choices are boiling, distilling, ozonating, or UV. Of these, UV is by far the safest and cheapest method, especially for RVers.

How Does A UV System Work?
A UV system consists of a UV light source and a device to enable the water to be exposed to the light. Most systems include a tube that the water passes through that has a long, thin UV fluorescent tube as its core. As with many things, the longer the water is exposed to the light source, the better job of sterilizing is achieved. For this reason, UV sterilizers are designed to get the maximum residence time of the water within the unit.

How Expensive Is UV To Operate?
The operational cost of UV systems is very low, as the only expense is the electricity to run the fluorescent light.  The only other cost involved is in replacing the UV tube. They are rated for 9000 hours, which is one year of continuous use, but even if you aren't a full-time RV'er, you should still replace the tube once a year, as they do deteriorate.