Dry Bag
A dry bag is a waterproof container with a roll-top closure that traps air and seals when folded and clipped.
It is the reliable way to keep electronics and a change of clothes dry when your outer bag is not waterproof, which most rucksacks and panniers are not despite what the marketing implies.
Why the roll-top matters
The seal comes from rolling the opening down at least three times before clipping. Fewer rolls and it leaks. This is the most common user error, and it is why a dry bag that failed usually was not closed properly rather than being faulty.
Where it beats a rain cover
A rain cover sits on the outside of a rucksack and does nothing about water running down your back and in through the opening, which is the main route water takes. A dry bag inside the pack protects the specific things that matter regardless of what the pack does.
Sizes worth carrying
A small one, around 3 to 5 litres, for phone, documents and a battery. A larger one, 10 to 20 litres, for a change of clothes if you commute by bike. Anything bigger is usually a pack liner rather than a bag.
Related terms
- Cycling to work in the rain: where a dry bag beats a rain cover
- How to dry clothes while travelling: what to do when something does get wet
- Glossary: all terms