Nope. when my dog is in the field he drinks what he drinks.. Given that he's a dog and licks other
dogs butts as a greeting, and rolls in horse dung for fun, I figure he can deal with whatever's in the water.

Given that I don't even usually purify above the treeline, if I were in the habit rolling in horse poop, and greeting other hikers as my dog greets other dogs, I probably wouldn't worry about the water either.

Mind you I'd probably get arrested.. or there'd be this massive RCMP manhunt in the rockies and a "mad hiker" movie starring Lee Marvin...