I carry my water in a 1L platy with a Sawyer in-line filter on the drinking tube. I keep the platy inside my pack, on top of everything else, with the tube snaked out through the port down my shoulder straps.
Where I hike, 1L is almost always more than enough water, so I rarely fill the thing completely, unless I know there won't be water for awhile, or I am unsure.
As for the thing leaking, all of the gear in my pack I don't want to get wet goes in a drybag. Everything else I expect to get at least somewhat wet if I get rained on, so if the platy leaks, I really don't care, provided the leak is not catastrophic enough to render the bladder useless. I do generally carry a second 1/2L platy as a backup and also to drink from during meals.
No desert experience here though, if you're in doubt about water availability, carry a lot. If you're walking along a reliable creek though, I wouldn't carry more than a liter (probably much less).