Waterproofing & Rain Protection: Complete Guide

Hiking backpacks are water-resistant, not waterproof: the face fabric sheds light rain thanks to a DWR coating and sometimes a PU or silicone backing, but the stitched seams, zipper coils, and back-panel mesh are not sealed and let water in once rain is sustained or heavy. Only fully taped, roll-top dry bags are genuinely waterproof.

Most hiking packs use ripstop nylon or polyester with a polyurethane (PU) or silicone coating on the inside face and a DWR (durable water repellent) finish on the outside face. That combination beads water off the surface and blocks it from soaking through the weave for a while. It does nothing for the holes a sewing needle leaves at every seam, and it does nothing for a zipper's coil teeth, which pass water even when closed. Packs built from Dyneema Composite Fabric (DCF, formerly Cuben Fiber) are the exception at the fabric level — the laminate itself doesn't wet out — but DCF packs still rely on sewn or taped seams and a roll-top closure instead of a zippered lid to keep water out, so the pack as a whole is only as waterproof as its weakest seam.

A rain cover stretches over the outside of the pack to keep the shell fabric and any gear lashed to the exterior from soaking through; a pack liner lines the inside of the main compartment so the gear inside stays dry no matter what happens to the shell. Most experienced hikers carry both.

A rain cover is an elasticized nylon shell, usually sold separately by size, that pulls over the loaded pack like a shower cap. It blocks direct rain from soaking the face fabric and keeps items strapped to the outside — a sleeping pad, wet-weather layer, or trekking poles in a side pocket — from getting drenched. Its weak point is the back panel: a rain cover can't wrap the side that rides against a hiker's back, so wind-driven rain and water wicking up from a wet trail or a pack set down on damp ground can still reach the pack there. A pack liner, by contrast, is a heavy-duty bag — a trash compactor bag, a contractor bag, or a purpose-built roll-top liner — placed inside the main compartment before packing. It doesn't care what the shell does; if the liner is sealed and the top is rolled or twisted shut, the contents stay dry even if the pack's fabric and seams are soaked through.

• Rain cover: protects the shell and exterior-lashed gear; leaves the back panel exposed; can shift or fill with water in wind
• Pack liner: protects everything inside the main compartment; unaffected by seam or zipper leaks; doesn't protect gear strapped outside
• Combined system: liner guarantees dry gear inside; cover keeps the shell lighter by absorbing less water and shields exterior straps and pockets

Reproof a pack's DWR by washing the pack clean first, since dirt and body oils block a new coating from bonding, then applying a wash-in or spray-on DWR product such as Nikwax TX.Direct or a comparable treatment, and finishing with gentle heat from a low dryer cycle or an iron on a synthetic-safe setting if the product label allows it.

DWR wears off gradually through abrasion against brush and rock, sun exposure, and accumulated dirt, so a pack used for weekly trips may need reproofing once or twice a season, while occasional use can stretch that to once a year or less.

Keep electronics dry by packing them inside a dedicated waterproof pouch or a zip-top freezer bag and placing that bag inside the pack liner with the rest of the gear, not in an exterior pocket, since exterior pockets and even "water-resistant" zippered compartments are the least protected part of any hiking backpack.

Phones, cameras, GPS units, and battery packs are the gear most worth double-protecting, since water damage to electronics is usually permanent and often trip-ending. A phone-specific waterproof pouch with a roll-top or clip seal works well for a device used often during the day, since it can stay accessible in a hip-belt pocket while still keeping rain and splashes out. For gear used less often, a simple zip-top freezer bag inside the main pack liner is enough, and the redundancy matters: if the pack liner's seal fails at one corner, the inner bag is still a second barrier. Avoid relying on an exterior pocket alone, even a zippered one, since that's the part of the pack most exposed to rain and least likely to be sealed.