How to use a dry bag: the correct technique

A dry bag is only as waterproof as your technique: even a bomber welded-seam bag leaks if you fold it twice and clip it loosely. Here is how to do it right.

The roll-top closure: do it in four steps

The roll-top is the only moving part on a dry bag, and getting it right takes about ten seconds.

The most common mistake is treating the buckle clip as the waterproofing. The clip just holds the roll in place. The seal is the roll.

Air: purge it or keep it?

For most situations, purge as much air as you can before rolling. Less air means the bag compresses tighter against your gear, the top roll holds more firmly, and the bag fits better inside a pack.

The exception is flotation: if your dry bag is serving as a float for a packraft, a canoe thwart bag, or a swimmer's kit, leave a full air cushion. A bag with trapped air becomes a buoy. For those uses, seal with minimal purging and the air acts as insurance if the bag goes overboard.

For backpacking and kayaking day use where you are stuffing the bag into a pack, always purge.

The roll is the seal; the buckle just keeps it honest.

What belongs inside a dry bag

Prioritize by consequence of getting wet:

• Sleep system. A wet sleeping bag on a cold night is a genuine safety problem. A 5-liter dry bag around a compressible down bag is standard practice on any river trip or wet-weather thru-hike.
• Electronics and documents. Phone, GPS unit, emergency beacon, permits, and cash go in first, ideally in their own small inner bag.
• Insulating layers. A wet puffy jacket loses nearly all its insulating value. Pack it before you need it.
• Dry clothes to sleep in. Even on dry trips, a bag of clean sleep clothes you have never worn during the day is a comfort and safety margin.

Leave things that do not mind getting wet outside the bag: water bottles, trowels, tent stakes, sandals.

Using a dry bag as a pack liner

A pack liner turns your entire pack into a dry bag, which is more reliable than relying on a pack's built-in water resistance (most packs are shower-resistant at best).

For a 50-liter pack, a liner in the 30-liter range, like the Sea to Summit Lightweight Dry Bag 35L, fits inside the main compartment with enough extra material to fold down at the top once you load it. The side pockets and hip-belt pockets stay outside the liner, so keep anything in those pockets expendable.

When using a liner, pack the bag first, purge air, roll and seal it, then tuck the roll down into the pack and close the pack lid over it. The liner should sit sealed inside a closed pack, not with the roll exposed at the top.

Splash resistance vs submersion: know the difference

Most roll-top dry bags are rated for brief immersion (typically to 1 meter for 30 minutes under IPX7-style testing) when sealed correctly with four folds. That covers a bag tipping out of a canoe and being retrieved quickly.

Sustained submersion at depth, like a bag sitting on the bottom of a river for several minutes, will eventually push water past the roll. Welded-seam construction (no stitch holes, as on the SealLine Baja 20L) helps, but no roll-top bag is a scuba-rated pressure vessel.

Splash alone, meaning rain, wave spray, or a wet tent floor, is well within what a properly rolled bag handles. Two folds is enough for splash. Go to four folds any time submersion is possible.

Double-bagging is the right answer for truly irreplaceable items. Put the phone in a small waterproof phone case or a zip-lock-style inner bag, then put that inside the dry bag. The inner layer catches anything the outer layer misses, and the outer layer keeps abrasion away from the inner.

Frequently asked questions

For specific picks, see our guide to the best dry bags. Browse all hike guides or read how we research and rate gear.