Rain Covers FAQ's
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™.
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
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.
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.
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™..
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.