Dryhold buyer insight
Welded Waterproof Bag Seam Guide
Understand RF and HF welded waterproof bag seams, stress points, closures, reinforcement and practical sample review.
Map water exposure and load separately
A seam may be exposed to water without carrying much load, or carry a high load in a relatively dry area. Identify both conditions. Handles, shoulder straps and attachment points often need a different reinforcement strategy from the main waterproof panels.
Leave enough welding area
Panel shape, coating, thickness and tooling all influence a stable weld. Decorative details placed too close to a seam can reduce usable welding area or make production control more difficult.
Treat closures as part of the system
Roll tops, protected zippers and airtight zipper structures provide different access and protection. The closure must suit how frequently the user opens the bag and how carefully it can be closed in real use.
Review the sample under realistic handling
Load the bag, carry it, open and close it repeatedly, and inspect the high-stress transitions. Testing should match the agreed product claim; avoid using one generic test for every waterproof product type.