Check when the water meter was actually read. Many utilities do not read the meters every month, but will just bill an average amount. When they do finally get a real reading there may be a significant discrepancy between what they've charge out for the last few months and what the actual reading is. The discrepancy can go either way, and depending on what they've been charging out it can be a significant "correction".
When I moved into my previous shop my first month's gas bill was about 5 times what it should have been, I phoned and found out it was just a number they plucked out of the air since it was a new shop. I went out and did a reading for them and reported the number and they changed the charge to what was really used.