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I was out camping recently, and found that the bottom foot or so of my sleeping bag had gotten wet ( in part due to one of the stakes for my rain fly coming loose, but that's another story). As no one likes sleeping with feet in a wet sleeping bag, I was forced to curl myself up, which is an uncomfortable way to sleep as well.

That got me thinking; is it possible to waterproof a sleeping bag? I have some waterproofing spray that I used on my boots and part of a tent, and it says that it is usable on nylon, suede, leather, and Gore-Tex. I was wondering how effective it would be, and whether it would damage my sleeping bag in some way. I was considering only spraying the waterproofing on the bottom foot or so of the bag, since I had seen things mentioning that waterproofing can remove the breathability of the bag.

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    I'd try out putting the end of my sleeping bag in a large plastic garbage bag first.
    – ab2
    Apr 9, 2018 at 3:44
  • @ab2 That's such a simple solution, I didn't even consider it. I'll definitely try that, and it would solve the question of whether the water is from an external or internal source. I suppose that if the bottom stays dry, I could consider a less breathable but more significantly waterproof solution in the future.
    – fyrepenguin
    Apr 9, 2018 at 4:00

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TL;Dr

DWR on sleeping bags is to keep them dry for short periods when they get put on wet grass for a few minutes. Adding DWR to your sleeping bag won't make it waterproof.

Waterproofing spray (DWR). Aids water running off it won't make something that fundamentally isn't waterproof suddenly waterproof (despite what the manufacturer says). A lot of sleeping bags have some degree of DWR pre applied but it tends to wear off.

is it possible to waterproof a sleeping bag?

This depends on your definition of waterproof. Is it possible to make a sleeping bag totally waterproof? No.

Would this be a good idea even if you could? Well again no. You need moisture to escape your sleeping bag or else you'll wake up drenched in sweat in the morning.

Can you aid it's water repellency with sprays? A little.

Will this top your feet getting wet if your tent breaks? Probably not

would damage my sleeping bag in some way

This depends on your sleeping bag a little. Don't apply anything the manufacturer says you shouldn't.

That said it should be fine to add DWR to a sleeping bag.

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  • Do you think that it would be water repellent enough to stop it from getting soaked if the bottom of the tent manages to get wet? (assuming that the circumstances that led to that weren't in your control)
    – fyrepenguin
    Apr 26, 2017 at 13:37
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    In a word, no. If your really concerned by this you'll need a bivvy bag. though for me, the solution is fix your tent not waterproof your bag
    – user2766
    Apr 26, 2017 at 15:27
  • There are industrial sprays that claim to be able to waterproof a slice of bread, and are marketed for use on boots so might not be too toxic for a sleeping bag.
    – user8348
    Apr 26, 2017 at 16:53
  • @Liam I plan on addressing the tent as well, but in part, I'm pretty sure that someone accidentally knocked out the stake at the foot end of my tent, and that exposed the ground cloth. I'm also planning on re-waterproofing my tent, mind you, but I was curious whether the spray would help or not. A bivvy bag is probably excessive for my purposes.
    – fyrepenguin
    Apr 26, 2017 at 19:54
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    @Liam I hadn't seen the term DWR before, so that was a good thing to look up. REI had a good article on it, and that explains a fair amount to me about what you mean.
    – fyrepenguin
    Apr 26, 2017 at 19:57
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The DWR will probably not alter its breathability, especially considering that sleeping is quite static.

Depending on how the bag got wet, it won't help that much as it can wet out after some time anyway and can wet out through the seam.

That being said: I don't see any negative effects of applying a DWR, only a slightly positive one.

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  • There was a ton of rain, and some soaked through my tent, but only the bottom of my sleeping bag actually got wet. Preventing something like that, as a last-ditch effort if all the rest of the rain protection fails, is what I was going for.
    – fyrepenguin
    Apr 26, 2017 at 13:34
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I would strongly caution against anything which might affect the ability of the sleeping bag to breathe.

You sweat while you sleep, and I don't think most of us realize how much. Sleeping bags are designed to be porous, and anything which might alter this could be dangerous.

I had a friend who decided to use a mylar emergency blanket on top of his sleeping bag one night (it was colder than he was prepared for). When he woke up in the morning, his sleeping bag was soaked. Other than being disgusting, he also found that he was more than a bit wet himself. And did I mention it was cold outside? ;)

This is the same reason that wisdom suggests sleeping with as few clothes as possible. If you sleep in your clothing, they will be damp in the morning when you climb out of your sleeping bag.

The thought of waking up damp on a cold morning is not an enticing one.

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  • Would that be a problem even if I waterproof the bottom foot or so of the bag, rather than the whole thing?
    – fyrepenguin
    Apr 26, 2017 at 13:31
  • DWR wouldn't affect the breathability of the bag. It's simply a hydrophobic coating, aiding liquid water to run off. It won't make anything waterproof and it won't stop water vapour from escaping. This is the fundamental mechanism behind things like GoreTex, etc.
    – user2766
    Apr 26, 2017 at 15:24
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    A mylar emergency blanket is not DWR. It's a physical barrier, totally different thing
    – user2766
    Apr 26, 2017 at 15:25
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Best I could advise is a plastic bag over the end of the bag. It it only gets wet at the bottom do to tent flap.

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There's one piece of equipment I've carried with me on every trip, even on day trips and that's a lightweight and durable rescue blanket. Not only can it help you to stay warm (shiny side in) but it can help you to protect yourself from heat (shiny side out). Being wind and water proof it makes a versatile friend you don't want to part from. I've used it to stay warm in snow storms by wrapping it around my sleeping bag but it also can be used to stay dry by doing just that. And it makes a great cooking shelter when combined with adjustable trekking poles and a couple of tent stakes.

Used as a cooking shelter

Used as a cooking shelter

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  • I actually use one inside my tent, below my sleeping pad. It helped a lot on the occasion that I was referring to, but enough standing water in the bottom of my tent ended up soaking the bottom of my sleeping bag. I've never tried wrapping it around me while I sleep, though.
    – fyrepenguin
    May 3, 2017 at 16:03
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Water proof spray would only help with the outside of the bag. Waterproofing is available that the bag is washed in which coats all the down with hydrophobic water repellant.

Or ready made ones are also available. https://www.youtube.com/watch?v=tn4BiDsVqyk

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I use Barbour wax on the bottom half of my sleeping bag, bivvi bag and fabsil gold on my tent outer and both on most clothing, Depending on what you want to water proof always test first.i always roll sleeping bag up in tent never out side is a pain but keeps it dry. perhaps getting a tent with a built in ground sheet would solve this problem.

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