On all the courses I have ever attended (including 3 Ray Mears courses) the advice was to never drink water without preparing it first. At the very least, you should use a fabric filter like a Millbank bag and then keep the water at a rolling boil for 5 minutes. You might get lucky once, you might get lucky a hundred times but there are some serious bugs found in water and it's not worth the risk.
For the record, I use one of http://www.raymears.com/shop_item_desc.cfm?id=87&itemType=Water&desc=Pre-Mac_MWP_Water_Purifier_Pump
Hi, are those Ray Mears courses good? Are the people friendly? I was thinking about doing the Ardeche course, but none of my friends want to join me so I would have to go by myself.