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Dry Bag Buying Checklist

Start with the exposure, not the bag

The most common buying mistake is choosing a volume first and hoping it is waterproof enough. Reverse it. Write down the worst water event the bag will meet in a normal season: a jet of spray at the bow of a kayak, an hour of motorway rain on a rack, a short immersion when a canoe tips, or nothing more than a wet grass verge at a festival. That single sentence sets the rating you need and eliminates half the market immediately.

Two caveats keep this honest. First, rate the worst realistic event, not the worst imaginable one: specifying for a two-hour submersion when the bag will meet spray costs mass and money for protection you never use. Second, remember that a bag can be downgraded by misuse. A welded IPX7 bag closed with one fold performs like an IPX4 bag, so the rating you buy is the rating you get only if the closure is used properly every time.

Closure: the part that fails first

Look at three things: the height of the mouth band, the number of fold lines marked into it, and the buckle. A reinforced band of roughly 45 mm gives the fold something to press against and stops the roll walking; below 35 mm the closure tends to unroll under load. Three fold lines marked into the film tell the user how far to roll without guessing, which matters more than any instruction card.

The buckle should be a centre-release rated to at least 250 N, not a ladderlock or a clip that needs two hands and good light. Side-release buckles on the ends of the roll are the standard for a reason: they can be worked with cold, wet fingers and they cannot be cross-threaded. If a bag uses a hook-and-loop strip as its only closure, treat it as splash-proof regardless of what the listing says; hook and loop loses grip when it is packed with sand.

Seams: welded, taped or stitched

This is the line that separates a waterproof bag from a water-resistant one. A welded seam fuses film to film so there is no path for water at all; a taped seam covers needle holes with an adhesive strip that degrades with heat, flex and age; a stitched seam with a coating relies on the coating, and needle holes are exactly what a pressure gradient pushes water through when the bag is squeezed under water.

You can identify a welded seam by feel in a shop and by zooming in on a listing photograph. Welded joins are flat, have a slight gloss change along the band, and often show a fine parallel line where the electrode pressed. Taped seams sit proud of the surface and usually have a visible edge that can be lifted with a fingernail after a season. The seam detail photograph on this comparison shows both side by side.

Fabric and film: the two numbers that matter

Every dry bag is a laminate: a face fabric for abrasion and a film for waterproofing. Both numbers matter and they do different jobs. The denier of the face fabric describes the yarn thickness, so 420D resists abrasion and 500D resists more, at a mass penalty of about 40 g per square metre. The film thickness, usually 0.3 mm to 0.6 mm, decides puncture resistance and how the bag behaves when folded in the cold.

Choose the film for the cold, not just for the abrasion. TPU stays flexible well below freezing, while PVC stiffens noticeably around 0 °C and creases permanently if it is folded hard when cold. If the bag will live on a boat or a bike through a winter, the film choice is a bigger decision than the denier. Material behaviour in cold conditions is covered in more depth in our cold crack note.

Capacity: the number on the label versus the number you get

Stated volume is measured with the bag open and full to the brim, which is not how anyone uses it. Rolling the top three times consumes 12 to 20% of that figure: a 20L roll-top realistically holds 16 to 17 litres, and a 10L holds about 8.5 litres. Buy on usable volume, and if you have a load of 14 litres to protect, the 20L is the correct size, not the 15L.

The second correction is packing efficiency. Soft items compress, rigid items do not, and a bag containing a camera body, a lunch box and a fuel bottle will not close at its theoretical limit. Work on 85% of the usable figure for mixed loads and 95% for clothing only. The capacity measurement note sets out how the figure is derived and why two brands can quote different numbers for the same physical bag.

Hardware: buckles, rings and strap anchors

Hardware fails more often than film, and it fails at the attachment rather than in the component. The check is the footprint: a welded webbing tail spreads load over several square centimetres of film, while a small plastic loop concentrates it into a few millimetres and tears out under a shock load. Pull on every anchor in the shop. If the film whitens around the weld, the footprint is too small for the load the bag will actually see.

Decide whether you need a valve at all. A purge valve lets you compress a soft load after closing, which is useful in a kayak hatch and pointless in a bag you carry on your back. Every valve is one more seal to leak and one more cap to lose, so the default answer for most buyers is no, with the exception of expedition use where compressing a sleeping bag matters. The trade-off is set out in our valve comparison.

Ratings: demand the standard, not the adjective

A listing that says waterproof, ultradry or stormproof has told you nothing. What you want is a code, a test and a duration: IPX6 against powerful jets, IPX7 for 30 minutes at one metre, IPX8 at a depth the brand states and tests to. These grades are defined in IEC 60529, published by the IEC, and the fabric and coating test methods behind a hydrostatic head figure are published by ASTM.

If a hydrostatic head number is quoted instead, read it correctly. A head of 10,000 mm means a column of water 10 metres high before leakage under a static test, which is a material property and not a guarantee about the closure. A bag can be built from 10,000 mm fabric and still leak through a badly rolled top. Ask what was tested: the panel, the seam, or the whole bag closed. Only the last of those predicts what will happen to your sleeping bag.

Weight, packed size and the carry question

Compare mass at the same volume, because the spread is large and it tells you what you are buying. A 20L bag at 280 g is built from light film and will be a liner; the same volume at 620 g is an expedition build. Most buyers are best served in the middle, around 400 to 500 g for a 20L, which buys 0.4 to 0.5 mm film and a 420D or 500D face without punishing you on a long carry.

Then decide how you will carry it. A roll-top with a single shoulder strap is fine for 500 m from a car park to a beach. Above 4 kg, or above 800 m, you want a proper harness with 40 mm webbing and a sternum strap, and above 8 kg you want a duffel with backpack straps so the load sits close to your spine. Format choice is unpacked in our backpack versus duffel guide.

Colour, UV and heat behaviour

Colour is a functional choice on the water and an aesthetic one everywhere else. On a boat, a bright bag is easier to spot in the water and easier to find in a dark hatch, so orange, mint or blue have real value. On a bike rack or a dusty overland trip, dark matte film hides road film and looks presentable after a week without a wash. Pale colours show abrasion as grey scuffs long before the material has actually worn through.

UV is the slow killer, and dark colours absorb more of it. A black bag left on a deck all summer can reach 70 °C at the surface, which accelerates film ageing considerably; the same bag in mint or grey runs cooler. Neither will fail in a season, but if your bags live outdoors year-round, prefer a mid-tone and store them out of the sun. The mechanism and the numbers are in our UV prevention guide.

Care, repair and spare parts

Ask two questions before buying: can the closure be replaced, and can the bag be patched. A welded bag with a standard buckle can be re-buckled in two minutes with a part that costs very little; a bag with a proprietary closure becomes rubbish the day the buckle cracks. TPU patches with a heat press or a suitable adhesive repair most punctures permanently, while PVC needs a solvent weld and patched PVC rarely lasts.

Then check the care instructions. If a bag is described as machine washable, be sceptical: agitation abrades film and twists welded seams, and no serious welded bag benefits from it. Hand rinse at ambient temperature, dry in shade with the mouth open, store rolled loosely rather than folded flat. The full routine, including what to do about mildew, is in our cleaning guide.

Price bands and what changes at each step

Retail price tracks film thickness, seam method and hardware quality far more closely than it tracks brand. What follows is a realistic spread for a 20L welded bag bought in a single unit, not a trade price. The point of the table is not to tell you to spend more; it is to show which defects appear at each level, so you can decide which ones you are willing to accept for a bag that will be used twice a year.

The most useful thing to do with this table is to decide where your use sits and then refuse to pay for the band above it. A bag for two beach holidays a year does not need expedition film, and a bag for a rental fleet does. Buyers who overspend are rarely disappointed by the bag; buyers who underspend by two bands usually are, because they end up buying twice. Our price breakdown goes through the cost structure line by line.

Red flags in a listing

• Waterproof claim with no rating and no standard named anywhere on the page.
• Photographs that never show the inside of a seam or the closure in the rolled position.
• A stated volume with no dimensions, or dimensions that do not produce the stated volume.
• Stitched seams described as sealed, which usually means taped over needle holes.
• A hydrostatic head figure quoted with no test method or no date.
• Reviews mentioning wet contents after light rain, which points to the closure, not the film.
• No spare buckles or patch material offered for a bag sold as repairable.

One more signal is worth adding, and it is not on the listing at all: how the seller answers a technical question. Ask which standard the rating was tested to and what the film thickness is. A seller who answers both within a day is dealing in real specifications. A seller who replies with adjectives is selling a photograph. The same questions are set out for spec sheets in our spec sheet guide and in the red flags article.

The twelve-point checklist to run before you pay

1. Name the worst realistic water event and the rating it requires.
2. Confirm the seams are welded, not taped over stitching.
3. Check the mouth band is at least 45 mm with three marked fold lines.
4. Confirm the buckle is a centre-release rated to 250 N or more.
5. Read the film thickness: 0.4 mm for everyday, 0.5 mm for abrasion.
6. Read the face fabric: 420D minimum for regular use, 500D for heavy use.
7. Convert stated volume to usable volume and check it against your real load.
8. Pull every anchor and check the weld footprint for whitening.
9. Weigh the bag and compare at equal volume, not across sizes.
10. Choose colour for function: bright on water, dark and matte on roads.
11. Confirm spares: a standard buckle and a patchable film.
12. Ask which standard the rating was tested to, and get the answer in writing.

Run those twelve in order and most buying decisions resolve themselves in ten minutes. Two of them, the seam type and the rating evidence, do about 70% of the work; if a bag passes both and fits your load, the rest is preference. If it fails either, no amount of good hardware or attractive pricing will make it keep your kit dry, because those two items are the waterproofing and everything else is convenience.

For anyone buying more than a couple of bags, the same list becomes a purchasing specification, and the answers belong in writing on the order: seam method, film thickness, closure geometry, anchor footprint, test standard, and the AQL level applied at inspection. We have produced waterproof bags to specifications of that shape since 2014 in an SGS-verified 4,950 m² facility, with a 500-piece minimum, sampling in 6 to 10 working days and bulk in 35 to 50 days at AQL 2.5.

Finally, test the bag the day it arrives. Roll it three times, squeeze and listen for a hiss, then submerge it in a bath for 30 seconds with a dry paper towel inside. That takes five minutes and it is the only check that matters, because it tests the bag you were actually shipped rather than the one in the photograph. Everything else on this page is a way of narrowing the field before that test. Compare what you find against the full product line, and use the features-to-skip guide if a listing is trying to sell you extras you will not use.