Do I need a water filter?
The pristine nature of the west coast trail may look innocent but the shear amount of people and wildlife that frequent the fresh bodies of water makes the likelihood of parasites very probable. There are a number of methods to getting clean water but the three mentioned here are probably the most trail friendly to execute.
BOIL : FILTER : PURIFY
Every morning when cooking your breakfast (or whatever) boil a few litres for 5 to 10 mins to assist in killing off the bugs, and except for a few places, there always seemed to be places to access the myriad of creeks and rivers along the way. We were quite confident with the filter but did at times (especially in areas where the was the potential for people bathing was great) add a purifying tablet to our camel backs.