Milton is the best, you can get water tablets but if its good enough for the army drinking dirty water with milton, then its good enough for us. Add some as directed to a couple of litres in your hog - then run the pump. If you have on-board tanks then the same applies to the on board tank. Hey presto! Clean pipes. Fill your hog again with fresh water, then rinse. Some people do it again. It's up to you - you cant be too clean.
Also - change your filter (inline, truma or at your whale submersible), not that a filter does anything but stop bits getting into your supply but because germs can grow in there. It's a good idea to remove the filter completely then run the milton as a new filter wont need it and its not recommended by the manufacturer. If you have no filter then invest in one - you can get in line one's good enough for a season for £20-£30 and its just a case of cutting your pipe and putting it in between. They dont kill germs but I felt when I had one it made the water taste a bit nicer.
I have bought some clean water tablets, every trip out my first hog fill has a couple dropped in for luck. They are tasteless and provide that piece of mind.
It may taste a little miltonny for a couple of fills but we have never got bugs and we have had babies in our vans (well not literally).
My wife wont drink water from the hog but I do and have never had any problems at all.
we always use Milton before we go out in the van, and we also draw the milton through the taps to make sure bthe pipes are clean, and we have never had any bugs.
------------- "PACESETTERS" German Shepherd dog display team, we are out and about raising money for guide dogs.
milton is fine, just make sure you rinse out the water heater well, if left in contact with the tank, it will corrode it, if its rinsed will it will be fine.