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How Brands Claim Waterproofing

The vocabulary of waterproof claims, ranked by strength

Claims form a rough hierarchy, and the useful habit is to translate each one into the test it implies. At the bottom sits water-repellent, which means a finish that makes water bead and run off; it has no pressure rating at all and fails within seconds of contact under load. Water-resistant is the next step up and usually implies some spray testing, but no standard threshold exists, so two products with the same label can differ by an order of magnitude.

Waterproof is the strongest common word and should mean the item resists water penetration under defined pressure for a defined time. Above it sit the rated claims: IPX6, IPX7 and IPX8 from the ingress protection system, and hydrostatic head figures quoted in millimetres. These are the only claims that can be checked against a written protocol, and they are the only ones worth comparing across two products.

Everything else is decoration. Stormproof, all-weather, monsoon-ready and marine-grade are marketing constructions with no test method behind them. That does not make them dishonest by definition, but it does mean they carry no information, and a brand quoting them instead of a number has told you something about the strength of its evidence. Our water-resistant versus waterproof comparison sets out where the real line sits.

The four test families behind the numbers

Almost every waterproof claim traces back to one of four methods. A spray test wets the surface from a fixed nozzle and rates beading against a photographic standard. A shower test is its bigger sibling, spraying a larger volume from above for a set duration, often five minutes at 10 litres per minute. A hydrostatic head or water column test presses water against a clamped fabric sample and records the height in millimetres at which the third drop appears.

The fourth family is immersion, which is what IPX7 and IPX8 describe: the whole finished article goes under water for a defined period at a defined depth. This is the only family that tests the seams, the closure and the geometry rather than a flat swatch, which is why it is the only one that predicts field behaviour on a boat. A fabric that scores 20,000 mm on a column test can still belong to a bag that leaks, because the water did not enter through the fabric.

Understanding which family produced a number is the whole skill. A 5,000 mm hydrostatic head sounds impressive and means the fabric resists a 5-metre column of static water at that spot; it says nothing about a seam, a buckle, or a rolled closure. A bag quoting IPX7 has had its whole construction tested, including the weak points. See the mechanics in our hydrostatic head explainer and the water column test basics.

IP and IPX ratings in plain language

The ingress protection code is published by the IEC as IEC 60529 and grades enclosures against solid objects and liquids. The second digit is the water grade, and an X in the first position means the solid grade was not tested, which is normal for bags. IPX4 covers splashing from any direction, IPX5 covers low-pressure jets, IPX6 covers powerful jets, IPX7 covers temporary immersion, and IPX8 covers continuous immersion at a depth the producer specifies.

Two details trip people up. IPX7 is not automatically better than IPX6 for a surface use case, because the two tests measure different things: a bag can pass a 30-minute immersion and still fail a directed jet if its closure geometry deflects water under pressure. And IPX8 is not a fixed depth; the standard requires the producer to state the depth and duration, so an IPX8 claim without those two numbers is incomplete by definition.

Hydrostatic head: reading the millimetres

A hydrostatic head figure is the height of a water column a fabric withstands before leaking, measured on a clamped swatch with the water pressure rising at a standardised rate. Ten thousand millimetres corresponds to about 0.98 bar, and it is a genuinely useful number for comparing fabrics. It is not, however, a measure of the finished bag, and it degrades with abrasion, folding and contamination far faster than most people expect.

The useful threshold depends on where the pressure comes from. Sitting on a wet groundsheet generates roughly the equivalent of 1,000 to 2,000 mm under a kneeling load. A shoulder strap pressed against a wet back under a loaded pack reaches perhaps 3,000 to 5,000 mm. Immersion at one metre is near 10,000 mm at the deepest point. So 5,000 mm is adequate for rain and questionable for submersion, and 10,000 mm or more is the sensible floor for a bag that will genuinely go under.

Abrasion is the hidden variable. Measured after 5,000 rubs on a standard abradant, a coated fabric that started at 6,000 mm can drop below 3,000 mm, while a 0.50 mm laminated film holds most of its figure because the barrier is thick. Any serious specification should quote hydrostatic head after abrasion as well as new, and that second number is the one that predicts a complaint two years later.

How test conditions change a result

Taken together, these variables mean an honest 8,000 mm result can be presented as anything from 6,000 to 12,000 mm without technically lying, simply by choosing the rate of rise, the conditioning and whether the best or the median specimen is reported. That is why the method reference matters more than the headline figure, and why ISO 811 and ASTM D751 exist: they pin the conditions down so two numbers are comparable.

Claims that sound technical but carry no information

• Military-grade waterproofing: no recognised military standard for bags exists; the phrase has no test attached.
• Tested to extreme conditions: no depth, duration or temperature, so nothing can be reproduced.
• Waterproof fabric: true of the material and silent about the seams, which is where bags leak.
• Sealed seams: sealed with what, tape or weld, and tested to what pressure?
• Submersible to 10 metres: for how long, and did the closure hold or was the sample clamped shut?
• Laboratory certified: certified by whom, against which protocol, and is the certificate dated?

Each of these can be rescued by adding two numbers, and a credible brand will add them when asked. If the answer to what depth and for how long is a shrug, treat the claim as untested and price the product accordingly. This is not cynicism; it is simply the difference between a specification and a slogan, and only one of the two survives contact with water.

Why a rating on new material is not a rating in year three

Waterproof performance declines with use, and the decline is measurable. Welded seams lose strength mainly at corners and fold lines, typically retaining 85 to 95% of initial peel value after three seasons of weekend use. Coated fabric loses hydrostatic head through abrasion and hydrolysis, sometimes by half. Closures are the fastest-degrading element of all, because the roll-top mouth is folded and unfolded hundreds of times a year.

A sensible way to express this is a two-number claim: the rating when new and the rating the product is designed to hold after a defined service period. Very few brands publish the second figure, which is a shame, because it is the one that matters to a buyer deciding between two products at similar prices. Our own guidance on how waterproof ratings degrade goes through the mechanisms in detail.

There is a maintenance dimension too. A bag rated IPX7 when new will not pass that test with sand in the closure, with a fold taken across a crease, or with a buckle that has lost tension. Every one of those is user-preventable in under a minute, which is why the care instructions that ship with a bag are part of the claim rather than an afterthought to it.

Immersion testing and the 30-minute convention

The IPX7 immersion test is deceptively simple: submerge the article so its lowest point is one metre below the surface, hold for 30 minutes, then inspect the inside. Simple as it is, the result depends on details that are easy to get wrong. A bag with trapped air floats, so it must be weighted or held down; a bag that is overfilled has a strained closure that would not be closed that way in use; and a bag tested at 5 °C behaves differently from one tested at 30 °C.

Pressure is the reason depth matters. At one metre the outside pressure is about 1.10 bar, a 10% differential against the air inside the bag, and that differential is what pushes water through any microscopic path. At five metres the differential is 50%, which is why a depth rating without a duration is meaningless: many constructions survive a deep dip and fail a long shallow soak, because time lets capillary action do the work that pressure alone cannot.

For a buyer, the practical version of this test takes a bath and a brick. Fill the bag to about 85%, close it exactly as you would on the water, weigh it down, wait 30 minutes, then dry the outside and open it over a towel. That reproduces the essentials of the laboratory protocol and catches nearly every closure problem. More variants are in our immersion testing guide and the at-home test routine.

Reading a specification sheet like an engineer

A good specification sheet answers five questions without being asked: which test, at what value, on what part of the product, in what condition, and measured by whom. Anything less leaves room for interpretation, and interpretation always favours whoever wrote the sheet. The fastest audit is to look for a standard number: IEC 60529, ISO 811, ASTM D751, or an internal protocol that is described in enough detail to repeat.

Look next for the sample definition. A fabric result on a flat swatch is a material property; a result on a finished bag with seams and a closure is a product property. The second is typically 40 to 70% of the first, and the gap is where warranty claims live. If a sheet quotes only the swatch figure, assume the product figure is substantially lower and ask for it directly.

Finally, check who measured it. An in-house result is fine if the protocol is stated and the date is recent; a third-party laboratory report is better, and for programme buying it is worth requesting the certificate rather than the summary. Inspection standards matter here too: production is sampled to AQL 2.5 in our own line, which means the bag you receive is not a hand-picked sample. The relationship between lab and reality is explored in our field versus lab testing guide.

Questions to put to a bag maker before a volume order

1. Which standard and which grade, named exactly: IEC 60529 IPX7, ISO 811 at a stated head, or an internal protocol?
2. Was the test run on a flat swatch or on a finished bag including seams and the closure?
3. What were the water temperature, the duration and the depth, and how many specimens were measured?
4. Was the median or the best result reported, and can I see the full set?
5. What is the hydrostatic head after 1,000 and 5,000 abrasion cycles, not only on new material?
6. Is there a dated third-party report, or is this an in-house result?
7. What performance is the product designed to retain after three seasons, and is that written down?

A serious production partner answers all seven in a day and sends supporting documents without being chased. A vague answer to the second question, about finished product versus swatch, is the single most informative response you will get, because it tells you whether the brand has ever tested the thing it actually sells. Everything else follows from that.

It also pays to ask about inspection rather than design. A product can be well designed and inconsistently made, and in waterproof goods inconsistency is fatal, because one weak seam in a thousand is one ruined trip. Ask what sampling level is applied, what the acceptance number is, and whether every unit or a sample is leak checked. We have produced waterproof bags since 2014 in an SGS-verified 4,950 m2 facility, and we document the full process for every programme: sampling takes 6 to 10 working days and bulk runs 35 to 50 days.

Ten-minute field checks that mirror the lab

• Bath immersion: fill to 85%, close normally, weigh down, wait 30 minutes, dry the outside, open over a towel.
• Shower test: hold the closed bag under a running shower for five minutes from all sides, then check the inside.
• Air squeeze: close the bag and press firmly; a hiss at the closure means the fold is not sealing.
• Base pressure: place the loaded bag on a wet surface for an hour and check the base panel from the inside.
• Seam tug: pull firmly on both sides of each welded joint and look for whitening, which indicates stress.

Run the bath test twice a season and after any repair. It takes almost no time and it is the only check that exercises the whole construction, seams and closure together. A bag that passes in year five has told you something real about its material; a bag that fails has told you early enough to do something about it, which is the entire point of testing at all.

Writing an honest claim for your own product

If you are putting a claim on your own packaging, the discipline is simple and it costs nothing: state the test, the value, the duration and the condition. IPX7 to IEC 60529, 30 minutes at one metre, tested on finished bags, is a sentence that any competitor can verify and no regulator can challenge. Waterproof to 5,000 mm ISO 811 after 1,000 abrasion cycles is equally defensible and far more useful than a superlative.

Avoid the temptation to quote the strongest number you can find anywhere in the data set. Overstating a rating converts a satisfied buyer into a warranty claim the first time the product meets real water, and the reputational cost of one failed bag exceeds the margin on a hundred correctly labelled ones. Under-promise slightly, publish the method, and let the field results do the arguing.

Whatever the claim, the closure remains the weak link, and the honest thing is to say so in the instructions: three folds, no trapped air, no sand in the fold line. Our roll-top closure guide explains the mechanics, and the roll count analysis puts a number on the margin. Sizes and ratings for every platform are listed in the full product line, and the academy hub collects the testing material in one place.