I'll be going on a 7-month trip through Eastern Europe (Belarus, Ukraine, Russia), Mongolia and China. This will be mostly hosteling with some day trips here and there. The various guidebooks all gave stern warnings against drinking local tap water.
Normally, I would just buy bottled water as I go… but for 7 months, I am thinking of bringing along a water bottle purifier — something inconspicuous, easy to use and effective against all three types of baddies (viruses, bacteria and protozoa) – something like this:

What do you guys think? Great idea? More trouble than it's worth?
If I carry one — which one would be the least bulkiest? Mind you, since I will be traveling through cities, towns and villages, I will have good access to water so I won't need a huge bottle.
Thanks in advance.

