I don't use a hydration bladder anymore, but I do fill up a bladder for in-camp use. Where I camp, it can drop below freezing pretty much any night, so I had the idea of stuffing the bladder into my pillow sack, both to keep the water from freezing and to give my pillow some weight so it's less likely to slip away. I might put the water filter in there also if I can keep it positioned to one end so it doesn't jab me in the face.

I know it's a risk, having water close to the precious down quilt, but the pillow sack is effectively a dry bag, so that risk seems minimal. What I'm really trying to mitigate is leaking inside the pillow because I usually have extra clothes and stuff sacks in the pillow to bulk it up because I am a side-sleeper.

Has anyone tried this? Am I asking for trouble? Or is there a simple way to mitigate leakage so I can sleep without worry?