Do you want to know whether or not your backpack is really waterproof without having to go to the trouble of putting it in the bath or under the shower?

 

Backpacks have to meet a few basic requirements to be considered waterproof:

- The zips must be waterproof.

- The seams must be sealed or bonded, or sewn and then taped.

- The overall design should prevent water penetration.

 

Most manufacturers classify their zips as merely water-repellent. This means that, when testing whether they are waterproof or not, most backpacks fail at the first hurdle.

Up to now, genuinely waterproof zips were nothing short of unwieldy monsters – usually incredibly heavy and difficult to use.

But water-repellent zips also have their share of problems. Depending on how tightly the bag is packed, models with sealing lips have a tendency to straighten up, forming a gap that allows moisture to penetrate. Then there is the problem of closing the zip. If the zip is not completely closed, water can get into the interior through the opening.

The next challenge is treating the seams. A brief inspection of the inside of the bag or backpack will tell you if the seams have been treated properly. Is the seam taped? Sealed? Or bonded? Conventional, non-taped seams allow water into the bag, albeit slowly, through the tiny perforations made by the needle and thread.

Then there is the actual construction of the bag. Backpacks are generally carried on the back and are therefore designed to prevent water penetration from above (rain). So, even if they remain waterproof under the shower, submerging them in a bath of water will soon put an end to that.