Backpack Construction

Rain Covers FAQ's

Are backpack materials waterproof?

All backpack materials have a polyurethane (PU) coating and are waterproof to varying degrees. The only true fully waterproof packs are made of vinyl and have welded seams. Waterproof zips are available, but are very expensive and can more than double the price of the finished backpack. There are water resistant zips now available on the market often promoted as waterproof, however these have not been approved in the manufacturing of White Mountain Backpacks™.

Are the seams on backpacks Waterproof?

While not entirely waterproof, all interior seams on well made backpacks are bound with a polyurethane proofed nylon webbing that reduces water penetration to a bare minimum. If you think it necessary and wish to further waterproof the seams, you can seam seal all seams with a liquid silicon seam sealer, available from most outdoor stores.

Are backpack Internal Liners necessary?

Some backpackers avoid external rain covers completely and use internal liners instead. These less expensive internal liners are heavy gauge plastic bags similar to what you'd see as a garden waste or a survival bag. Others opt for Dry Bags, which are actually designed for canoe or kayaking trips. The dry bags are far more durable than plastic, but also weigh considerably more. The advantage of an internal liner? You still have ready access to the backpack. The disadvantage? The backpack is not protected on the outside.

What is the purpose of Bivvy Bags or Zip Lock Bags?

We recommend the use of water proof Bivvy Bags or Zip Lock Bags in all circumstances, especially with hiking backpacks. These will protect your gear from water and allow you to organise your backpack for ease of access. The use of different colored Bivvy Bags is recommended and will enable all your stored equipment to be color coded for ease of identification.

Are Rain Covers Necessary?

Most backpacks have a waterproof polyurethane (PU) coating, that means water won't penetrate the backpack, right? Well actually, NO! Polyurethane (PU) coatings prevent water entering through the fabric, but don't prevent water from getting into the backpack through the seams and through the zippers. Bear in mind that lower quality backpacks have less stitching over a given area, and use a inferior thread. Inferior threads are not tensioned enough to form a tight bond on the adjoining materials, and this can easily be demonstrated by gaps formed when gently pulling on these adjoining materials. When fully packed a lower quality backpack will expose these gaps and allow greater water penetration. A backpack with higher quality thread that is stitched and tensioned to prevent gaping will prevent excessive water entering the backpack, particularly if bound internally with a waterproof nylon tape stitched over the exposed seam, as in all White Mountain Backpacks™..

What is the correct Rain Cover Size Selection?

Care must be taken in selecting a Rain Cover size. If you strap gear on the outside of your backpack, you'll want to make sure that the Rain Cover will fit over all of the backpack, external attachments and all. A generic XL Rain Cover should be large enough to cover all the gear. A personal choice on size is one reason we do not sew Rain Covers to the backpack, another is that Rain Covers are generally only required in severe weather conditions.