Though water is considered vegan, Jains boil it first, because -
http://www.jainworld.com/jainbooks/guideline/26.htm
Jains, while performing Biyasan and any higher austerity have to drink only boiled water. First, water should be filtered and boiled and then cooled, Then they can drink it; that too, only before the sunset; not after that. They should not drink water in the nights. Of course, when water is heated once, all the countless beings in it, die. But according to the Jain doctrines, in boiled water beings will not be born and so will not die for a certain period according to the season. In unboiled water every moment countless creatures are born and they die. So if once the water is boiled further violence is avoided. The sin of killing creatures is committed only once if the water is heated; and this avoids the committing of that sin again and again. Thoughtful people incur a small loss if by that small loss they can get a large profit. Of course, we should not cause violence to creatures; but we cannot live without water; so minimizing sins, we should use water. If the use of hot water is necessary, it has to be used. Meaningless use is improper. Now-a-days, even great physicians and doctors prescribe the drinking of hot water. Boiled water is good for health. In china, today, in large hotels drinkimg-water is first boiled and then cooled.
If you want to know all about Perth's water supply a good webpage is
http://www.viacorp.com/perth_water.htm
and up to date news at
http://www.water.wa.gov.au/ 
