OP Over the past 10 years I have spent a lot of time investigating water systems for my TC. I first started with the expensive top end Dupont filter, the biological filter $60, used nano tube technology but found out later it was not rated for non safe drinking water, what's the point of that? It also used two charcoal filters at $30 each. These need to be changed twice a year, so it would cost 240 a year to operate.
Fortunately second attempt I found the Rainfresh drinking water system 2, model: USCS2. Cost: $150 Can. It uses two filters, the Biological filter is a Ceramic silver impregnated .3UM filter that at max. needs to be changed once a year and costs $35 (I've gone 3 years with no ill effects). This filter can be used on rivers and lakes and untreated water. Cost a year to operate max. $50.
The second filter is a large charcoal filter good for 6 months and costs $8. It works much better than the Dupont filter for removing taste from the water.
Side note FYI you don't want to use a charcoal filter on water you are putting into your storage tank as the charcoal filter will remove the city chlorine and this will allow nasties to grow in your storage tank. Use the charcoal filter just before you need the water.
Here is a link to Rainfresh it is Canadian company, I have not seen any of their systems sold in stores in the US (I haven't looked very hard), it is by far the most popular system here in Canada. http://rainfresh.ca/drinking_water_system_2.php