I don't think there's any problem drinking from the tap on your boat especially as its well used.
We have a stainless steel tank and use sterilizing tablets at each fill, but for added protection I fitted one of these http://www.purewateronline.co.uk/700008-X-1B-Seagull-R-IV-Basic.html.
Richard Parry drank canal water after it was filtered through it at one of the shows.
A bit expensive - got a discount on it a few years ago at the Crick show, but if there's 12 owners chipping in on your shared boat it might be worthwhile.