You'll see it mentioned in other threads about water filters, the King of water filters is the General Ecology, which claims to filter out to virus level. I have one, and haven't carried bottled water aboard since I installed it...
Not compared with the price of bottled water... our filter is about £50 to replace. The original kit included a nice quality separate tap for about £180 as I recall. You don't have to have the Seagull IV filter. Filters last for a volume of water, ours easily does two years for weekend and holiday use
