Dry Bag Manufacturer in China

Sealock is a dry bag manufacturer in China supplying OEM, ODM, and wholesale buyers worldwide. The dry bag is the oldest and simplest product in waterproof gear — a single welded chamber closed by rolling the top — and it remains the benchmark by which a waterproof factory is judged. There is nowhere to hide: no lining to disguise a bad seam, no zipper to blame. Either the welds hold and the closure seals, or the customer's sleeping bag comes out wet. This overview covers how a dry bag is built properly, what actually causes the failures buyers hear about, and the sourcing terms.

The Uncomfortable Truth About Dry Bag "Leaks"

Any brand selling dry bags will field complaints that a bag leaked. The evidence from testing is consistent and worth understanding before you spec a product: most leaks are not manufacturing defects — they are closure and loading errors. In side-by-side submersion tests a properly sealed bag stays dry while an improperly sealed one from the same batch leaks immediately.

Two user behaviours cause the majority of it:

• Not enough folds. A roll-top only seals when the opening is folded over itself at least three times before clipping — the pressed layers are the seal. Rolled once or twice "to save time", a perfectly good bag leaks every time.
• Overfilling. Stuff a dry bag to capacity and there's no slack left to fold. Forcing the buckle shut on a full bag doesn't create a seal at all. The working rule is to fill to about 80% and size up rather than squeeze.

The commercial implication for a brand is direct: printing the closure instructions on the product and packaging prevents more negative reviews than any specification upgrade. A bag that says "roll down 3–4 times, then clip" on the closure strip converts a support problem into a solved one.

That said, genuine build failures do exist — and they're the ones a buyer controls at the factory: stitched-and-taped seams whose tape lifts with age, pinhole leaks in seam construction, buckles breaking under normal tension, and coatings wearing through at abrasion points.

How a Dry Bag Is Built Properly

• High-frequency welded seams — panels fused at 27.12 MHz with no needle holes. This is the dividing line in the category: stitched-and-taped bags rely on adhesive tape that ages and lifts, while a welded seam is effectively part of the fabric. It's why a welded bag survives repeated submersion and a taped one degrades.
• A roll-top with a back-up seal — a fold-seal system, with a Velcro backing strip on some builds for extra security before the buckle closes.
• Material matched to the hazard — 500D PVC tarpaulin for abrasion and rock contact; TPU-coated fabric where light weight and cold flexibility matter. For kayaking and rafting, where contact with rock is likely, the heavier PVC is the safer specification.
• Buoyancy — rolled and buckled with air inside, the bag floats, so gear dropped overboard stays findable at the surface.
• Carry that scales with size — small sizes take a single adjustable cross-body strap; larger sizes need backpack-style double straps, and the biggest benefit from a chest strap for stability.
• Proof on the finished bag — a real water-submersion test, rather than a fabric figure. The construction distinction is set out in our guide to waterproof vs water-resistant laptop bag construction.

The Failure Points Worth Speccing Against

The Factory: Capacity and Certifications

• Dongguan: 12,000 m², 400+ staff, nine HF welding lines, output around 100,000 units per month; over twenty years in welded waterproof bags.
• Two Ho Chi Minh City, Vietnam plants for diversified origin and US-tariff mitigation.
• Exports to 40-plus countries; 20-plus waterproofing patents; OEM production for brands including SIMMS, PENN, West Marine, attwood and CHUMS.
• Certifications: SMETA P4, HIGG, SCAN, GRS, BSCI, ISO9001, with an IP-protection process for private-label programmes.

Dry Bag Range

These welded bags, from Sealock's dry bag line, cover the main formats and serve as equal starting points for an OEM order — none is ranked above another; pick whichever suits the use case and customize from there.

Roll-Top Tube Dry Bags

The classic single-chamber sack, offered across the full capacity ladder from a 2L pouch to a 100L expedition sack:

Note the range of options within one format: a transparent window where contents need to be visible, a fold-seal with a back-up Velcro strip for redundancy, a gas valve where controlled inflation matters, 70D nylon-coated PVC where weight is critical, and an IPX7-rated build with dry-wet separation.

Dry Backpacks

The same welded construction with a carry system, for when the load has to be walked or paddled any distance:

The two kayak models are worth noting for specification ideas: both carry a front window pocket for a phone, a multi-function lock for securing a paddle board, an inflation and deflation valve that lets the bag be filled with air for temporary flotation support, and a one-piece EVA back panel to cut weight and heat on the walk in.

Capacity, material, colourway, closure, pockets, carry system and branding are all specifiable per order. Capacity selection and the roll-down volume loss are covered in our custom waterproof camping bag buying guide, and the closure trade-offs in our guide to roll top vs waterproof zipper camping bags for oem projects.

Applications

• Paddlesports — kayaking, canoeing, rafting and SUP, where submersion is a matter of when, not if.
• Fishing and boating — wet decks, spray, and tackle abrasion.
• Camping and hiking — sleeping bags, clothing, and electronics kept dry through rain and damp ground.
• Beach and travel — sand, saltwater, and wet swimwear.
• Promotional and private label — bright, branded sacks at volume, one of the strongest promotional formats in outdoor.

OEM / ODM and Custom Development

Quality Control and the Customer Inspection Procedure

Quality is gated in three tiers — IQC (incoming tarpaulin, buckles and webbing against the signed colour card, with colour difference and fastness), IPQC (cutting tolerance, weld integrity and strap-anchor assembly on the line, with test welds before each run), and OQC (AQL sampling, a real water-submersion batch test, and gold-sample comparison, with SGS or QIMA inspection available). Sealock also strictly executes the complete customer inspection procedure on finished goods: unboxing, vacuum extraction, a 24-hour static rest, and air-leak determination — on a single-chamber welded bag this is the most revealing test there is, because a pinhole that passes a brief dunk still bleeds vacuum over a full day. The lab additionally runs weld bond and peel strength, a 1,500+ cycle load test with jerk-loading on strap anchors and buckles, abrasion, tear, tensile, salt spray, UV, colour fastness and colour difference.

FAQ: Sourcing Dry Bags

Q: Why do customers say their dry bag leaked?
A: Usually because the top wasn't folded over enough times, or the bag was overfilled so no slack was left to roll. In controlled tests, a correctly sealed bag stays dry while an incorrectly sealed one from the same batch leaks immediately. Genuine build failures are the minority — and they come from stitched-and-taped seams, not welded ones.

Q: How full should a dry bag be?
A: About 80%. The roll-top needs slack to make three or four folds; forcing a buckle shut on a stuffed bag doesn't seal it. Advise customers to size up rather than squeeze — and print the instruction on the product.

Q: PVC or TPU for a dry bag?
A: 500D PVC tarpaulin for abrasion resistance and rock contact — the safer choice for kayaking and rafting. TPU where lighter weight and cold flexibility matter, at the cost of some puncture resistance.

Q: Will a dry bag survive full submersion?
A: A welded roll-top bag, properly closed, handles immersion — that's what it's built for. It is not diving equipment, though: prolonged deep submersion is outside the design intent, and that limit should be stated rather than glossed over.

Q: How can we test bags on arrival?
A: Seal a bag with air trapped inside and hold it underwater; escaping bubbles mark exactly where water could get in, usually a seam or the closure. It takes a minute and is worth doing on every new sample.

Q: What are the MOQ and lead times?
A: Typically 300–500 pieces per model, samples in 7–15 days, and production around 30–45 days after approval.

Talk to the Factory

For quotations, samples, and OEM/ODM proposals on dry bags, contact Sealock at info@sealock.com.hk or +86-769-82009361. Over twenty years of high-frequency welding, nine welding lines, dual China–Vietnam production, and a full customer inspection procedure on every shipment.