Talk of water filters reminded me of our setup on back of Jeep: Mount a spigot like you find at any bottled water store for use in their ceramic containers for inverted water bottles. These come with nuts and rubber washers; just make sure what you buy is threaded all the way down, as a plastic 5-gallon jug is a lot thinner than the typical ceramic bottle holders they usually go into. Make sure you mount it high enough that it doesn't get damaged when the jug is on the ground for filling or a table for picnic use. The standard 5-gallon light blue water container we use (Why are graywater containers also blue?) is the same shape as a so-called NATO gas can, so fits in appropriate brackets on the external gas can / spare tire rack of the Jeep. This saves drips, spigot-breakage (it's protected by the rack), space, and repeated heavy lifting if otherwise inside. Road dust is an issue, so sometimes a baggie and rubber band are used. And, I wouldn't trust it if in a campground with juvenile delinquents, but we've had no trouble so far. Like your RV water tanks, just follow the usual bleach to water ratios for cleaning and for storage. World Health Organization (WHO) has some good, trustworthy info, as does the Center for Disease Control (CDC); here's one link that goes into the type and different amounts of bleach to use based on its concentration:
https://www.cdc.gov/healthywater/emergency/drinking/making-water-safe.htmlAnd, if I can do it on this android tablet or my new iPhone SE, I'll add a photo of the water container on the Jeep rack to this posting later if the link doesn't work.
https://goo.gl/photos/Zkjpf4PqPBMApbR29