I don't trust bottled water from unknown sources, so we filter the water from the regularly tested campground supplies to top off our fresh tank as needed. Our primary filtering is for sediment and chlorine taste removal, with secondary point of use drinking water filtering for lead, microbiological cysts, pharmaceutical traces, etc. The primary filter is a whole house housing with a Culligan D-20a filter rated for 1,000 gallons or one year, and our secondary filter is a PUR - the same as Dutch mentioned - rated for 100 gallons.