Is the compression sack that comes with my sleeping bag waterproof? Can I use it outside of a pack or bag?

All Sea to Summit sleeping bags come with a nylon Compression Sack (older models came with an Ultra-Sil Compression Sack).

The fabric of these compression sacks may provide some water resistance. However, the seams are not sealed and the pull-cord closure will allow water inside.

If either of these compression sacks are used inside a backpack, the degree of water resistance is adequate for backpacking in rainy weather – but not enough for soaking wet conditions (as you might encounter in Alaska, New Zealand or Norway, for instance). Because neither of these compression sacks are waterproof, they are not designed to be used outside of a backpack / bike bag / duffle bag.

If you would like to upgrade to waterproof storage for your sleeping bag, here are two recommendations:

• Evac Compression Dry Bag: This bag is waterproof / rugged enough to be suitable for use outside of a backpack or bike bag. It is made of a tough 70D nylon, and has a waterproofness rating of 10,000mm (hydrostatic head). Ideal use includes being mounted on handlebars in a bikepacking rig, or stowed in the hatch of a kayak.
• Evac Ultralight Compression Dry Bag: This bag is designed for use inside a backpack or bike bag. It is made of featherweight 30D Ultra-Sil nylon, and has a waterproofness rating of 2000+mm (hydrostatic head).
  
  

Both of these compression dry bags are seam taped and have a roll-top closure to keep your sleeping bag or insulated jacket dry.

If you need an extremely rugged storage option (for external use such as a motorcycle touring, snowmobiling, or rafting), we would recommend the Evac Heavy Duty Compression Dry Bag. This bag is waterproof and tough enough for use in anything but the most extreme conditions. It is made of a 420D ripstop nylon with a TPU laminate, and has a waterproofness rating of 10,000mm+ hydrostatic head.

Regardless of which compression dry bag you choose, always be sure to avoid submersion since water can seep through the roll-top closure of any dry bag.