Keeping hiking gear dry: pack liners, dry bags and ratings

Keep the things you need dry inside a properly closed liner or dry bag. A comfortable pack and a good rain jacket are useful, but your spare clothing and sleeping gear need their own protection.

What each item does

• Pack liner: a large waterproof bag that sits inside your backpack. It keeps the main load together. Match its shape and usable capacity to your pack.
• Dry bag: a separate bag for a group of items, such as warm clothes. Several small bags make it easier to find things and keep wet kit separate.
• Ordinary stuff sack: useful for organising gear, but do not assume its fabric, seams or closure are waterproof.

Look for the complete construction, not just a waterproof fabric claim. For example, Osprey’s Ultralight Pack Liner specifies coated fabric and seams plus a roll-top closure. Its small version is listed for 30–50 litre packs.

What the numbers mean

Litres (L) describe capacity, not protection from water. Leave enough space to close the top correctly; a tightly overfilled bag defeats the purpose.

Hydrostatic head, in millimetres (mm), measures the water pressure a fabric sample withstands before water penetrates. A higher number describes the tested fabric, not the whole bag’s closure or resistance to punctures.

Water-resistant is not the same as submersible. Sea to Summit warns that water can enter a roll-top closure and recommends separate protection for electronics. Check the exact product’s instructions for any immersion claim rather than treating all dry bags alike.

A simple way to organise the load

1. Inspect the liner for holes, worn coatings, damaged seams and a working closure.
2. Group dry spare clothes and sleeping gear inside. Follow the maker’s closure instructions.
3. Keep wet clothing and leaking containers separate from the dry compartment.
4. Protect your phone or camera separately, using a case suited to the conditions.
5. Make your rain layer easy to reach without unpacking everything in the rain.

I’d practise packing at home before a wet trip. Check the closure with the actual load inside, rather than finding out at the track entrance that the bag is too small.

If you are replacing the backpack itself, our tramping-pack guide explains fit, capacity and condition checks.

Sources and credits

Checked 27 September 2026: Sea to Summit’s dry-storage FAQs and Osprey’s Ultralight Pack Liner specifications.

Photo credit

Backpack photographed at the 2018 OutDoor trade show; not ReGear stock. Matti Blume, CC BY-SA 4.0.