Almost every pack on the market is described as water resistant, and almost nobody selling one explains what that means. The gap between the marketing phrase and a genuinely dry bag is where people lose laptops.

Level one: coated fabric

A polyurethane coating on the inside face of the fabric stops water passing through the weave. This handles rain on a ten-minute walk and a bottle that leaks inside the bag.

What it does not handle is the seams and the zip. Water finds the needle holes along a sewn seam and runs straight under an exposed zip, both of which are wide open on most packs sold as water resistant.

Level two: covered zips and taped seams

A storm flap over the main zip and seam tape heat-bonded over the stitch line closes the two obvious routes. This is a genuinely water-resistant pack and it will keep contents dry through most of a rainy commute.

It will still eventually wet out in sustained rain, because the fabric face saturates and the coating is working from behind. Hours, not minutes — but not a day on a hillside.

Level three: welded seams and a rolltop

No stitching through the body, no zip into the main compartment. The seams are welded rather than sewn, and the top rolls three times and clips, which is a closure water has no path through.

This is what couriers and outdoor guides use, and it is the only construction we will describe as waterproof. It costs more, it is heavier, and it is the correct answer whenever the contents genuinely cannot get wet.

The decoration trap

Embroidering a welded waterproof pack puts several thousand needle holes through the thing you paid extra to seal. It happens constantly because the decorator and the pack supplier are usually different companies and neither raises it.

On welded fabric, use screen print or a welded patch. We will refuse to embroider a waterproof body and tell you why.

Choosing without overspending

Office and campus commuting: coated fabric with a covered zip. Field staff, tour guides and anyone outdoors for hours: taped seams at minimum. Couriers, water sports and anywhere kit must stay dry: welded rolltop, no exceptions.

Buying a rolltop for a conference giveaway is money spent on a feature nobody will use. Buying a coated daypack for a courier fleet is a replacement order in six months.

What to check on any quote

Three questions settle it: are the seams sewn, taped or welded; is the main compartment closed by a zip or a rolltop; and how is it being decorated. A supplier who cannot answer all three quickly is reselling a catalogue they have not read.