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IPX Waterproof Ratings for Dry Bags

The IP code, read from left to right

The code is defined in IEC 60529 and has two digits after the letters. The first digit covers solid particle ingress on a scale of 0 to 6, the second covers liquid ingress on a scale of 0 to 9. A rating written IP68 therefore means dust-tight and protected against continuous immersion under conditions agreed between the tester and the client. When a brand writes IPX8, the X declares that the solid-particle tests were never run and no claim is made about them.

For soft goods the X is normal rather than suspicious. A roll-top dry bag has a closure that is opened and closed by hand, and sealing it against fine dust requires a completely different geometry from sealing it against water. Very few fabric products achieve a tested 5 or 6 on the solid scale, and the ones that do tend to use a screw closure or a welded zip rather than a roll-top. The IEC publishes the standard and the test fixtures, and a reputable spec sheet names it rather than inventing adjectives.

The number after IP is also worth checking for a second reason: IP69K, sometimes printed on hard cases, is a high-temperature high-pressure wash-down test designed for food-industry equipment. It has no meaningful application to a kayak dry bag, and a bag claiming it is almost certainly borrowing language from a different product category.

What each step of the second digit actually applies

The liquid scale is not linear. IPX1 and IPX2 are dripping water tests, IPX3 and IPX4 are spraying tests, IPX5 and IPX6 are jet tests, IPX7 and IPX8 are immersion tests, and IPX9 is the high-pressure hot wash. Each band uses different apparatus, different durations and different pass criteria, so moving from one number to the next is a change of test rig rather than a small increase in severity.

Two details from that table decide most buying decisions. First, the jump from IPX5 to IPX6 is a factor of eight in flow rate, which is the difference between a hose and a breaking wave. Second, IPX8 has no fixed depth at all: the standard says the conditions must be more severe than IPX7 and agreed between the parties. An IPX8 claim without a stated depth and duration is not a specification, and any brand making one should be asked for the number.

Which grades each bag format can honestly reach

Format sets the ceiling on the rating long before fabric does. A roll-top with three folds and welded seams is the strongest soft configuration and routinely reaches IPX6 to IPX7. A waterproof zip closure reaches IPX5 to IPX6 at best, because the zip teeth are a continuous mechanical path that has to be sealed by pressure from the slider rather than by a fold. A bucket bag with a stiff rim and no rolling closure sits at IPX4 to IPX5.

Waterproof backpacks are the format most often overrated. The body fabric and the seams may be genuinely IPX7 capable, but the shoulder straps are welded or stitched onto the back panel at four or more points, and each attachment is a stress concentration that flexes under load. A well-built welded backpack claims IPX4 to IPX6 for that reason, and a backpack claiming IPX7 on the whole product should be asked which part was tested.

Knowing the ceiling saves time. If you need IPX7, you are choosing between a roll-top bag and a rigid case. If IPX6 covers the exposure, a zip or a welded backpack becomes available and usually more convenient to pack. Decide the grade first, then let the format follow, rather than buying a shape and hoping the number fits it.

The jet grades: pressure, distance and where bags fail

IPX5 and IPX6 are performed with a nozzle held at a specified distance, typically 2.5 to 3 metres, and the sample is sprayed from several directions. The dominant failure point for a dry bag is not the panel fabric but the closure and the seam intersections. A welded side seam with a 20 mm flange survives easily; a roll-top folded only twice lets a jet drive water laterally under the second fold and into the body.

Distance matters more than buyers expect. The standard fixes it, but real conditions do not: a bow wave at 15 km/h delivers roughly the energy of an IPX6 jet at close range, while the same wave at the far side of a wide bay is closer to IPX4. This is why a bag rated IPX6 will still get a little water past the closure in a surf landing, and why the honest response is to add a fold rather than to claim a higher grade.

Immersion grades and the variable nobody prints

IPX7 is unambiguous: 30 minutes with the lowest point of the enclosure 1 metre below the surface and the highest point at least 150 mm below it. That second clause is the one that catches people. A tall bag tested upright in a shallow tank may have its closure only 200 mm under, which is a fraction of the pressure at the base. If the test report does not record the orientation and the depth of the topmost point, the result is not comparable.

Pressure is the hidden variable. Water pressure rises by roughly 9.8 kPa per metre of depth, so a bag at 1 metre sees about 10 kPa above atmospheric and a bag at 3 metres sees about 30 kPa. A closure that seals by contact pressure will hold until the external pressure exceeds the contact pressure at the fold line, which is why the same bag can pass IPX7 and leak when dragged 2 metres down by a current. Depth, not duration, is the demanding part of an immersion claim.

IPX8 therefore needs three numbers to be meaningful: the depth, the duration and the temperature of the water. A serious claim reads like an agreement, for example 3 metres for 60 minutes at 20 degrees Celsius. If a listing says IPX8 and nothing else, treat it as marketing and check whether the bag also carries an IPX7 result, which at least has a defined test behind it.

How a roll-top earns an immersion grade without a gasket

A roll-top is not a sealed enclosure in the way a phone case is. It creates a waterproof barrier by pressing two film surfaces together along three parallel fold lines, and the seal is generated by the stiffness of the fabric and the tension in the buckle rather than by an elastomer. Water has to travel laterally past three contact lines, each of which has to be forced open by pressure, and the resistance is cumulative.

This is why the number of folds matters more than the rating of the fabric. Two folds gives two contact lines and generally holds IPX5; three folds reliably reaches IPX6 and usually IPX7; a fourth fold adds little and costs volume. The closure also depends on being clean: a single grain of sand 0.5 mm across creates a capillary channel that defeats all three lines, which is why a bag that passes IPX7 in the laboratory can leak on a beach.

The closure mechanics guide sets out the contact-pressure maths in full. For the purposes of a rating, the practical takeaway is that an immersion grade on a roll-top is a property of the way the bag is closed on the day, not a fixed attribute of the product. Any test report should state how many folds were used.

Hydrostatic head, spray grade and immersion grade are three different tests

Buyers routinely confuse three numbers that measure incompatible things. Hydrostatic head, reported in millimetres of water column, measures how much pressure a flat clamped fabric sample takes before water appears at its third point of failure. An IPX grade measures a complete assembled product under a spray or an immersion. A 10,000 mm fabric can be made into a bag that fails IPX4 if the seams are stitched, and a 3,000 mm fabric can be made into a bag that passes IPX7 if the seams are welded.

Only one of those rows tells you where a leak is, and it is the last. An air inflation test at 10 kPa held for five minutes finds pinholes that an immersion test can miss entirely, because air escapes through a smaller defect than water will enter. The two tests are complementary, and a good quality process runs both. Our notes on the air inflation leak test describe the setup.

Fresh water, salt water and the temperature the lab used

IEC 60529 specifies fresh water for the tests, at a temperature within a few degrees of the sample. Neither condition matches the field. Salt water is about 2.5 percent denser, so it applies marginally more pressure at the same depth, and more importantly it leaves crystals in the fold line when it evaporates. A bag that passes IPX7 in fresh water and is then used daily in the sea will fail sooner, not because the fabric changed but because the closure is no longer clean.

Temperature affects the result through the film. A TPU laminate stiffens as it cools, which raises the force needed to form a flat fold but also raises the contact pressure once folded. The net effect at 5 degrees Celsius is usually neutral to slightly positive for a properly rolled closure and negative for a hurried one, because a stiff film will not conform around grit. Standard laboratory practice is 20 to 25 degrees, and any test report should state the temperature it used.

How far a rating drops after a season of use

A rating is a measurement of a new sample. In service, four mechanisms erode it: crease fatigue at the fold line, UV embrittlement of the film, abrasion of the face yarn, and relaxation of the buckle tension. The first two are the important ones, and neither is visible from the outside until the bag fails a test.

Read together, that table says something useful: most rating loss is preventable and almost all of it is about the closure rather than the fabric. A bag that is rinsed, dried in shade and stored loosely will hold its original grade for years. The same bag left salty on a roof rack will drop two grades in a season. Rinsing after salt water is the single highest-value habit.

Reading a bag label: the four facts that must be present

A waterproof claim is worth reading only if it carries four pieces of information: the grade, the standard it was tested to, the configuration of the sample, and the name of the laboratory or the internal test method. Three of those four are missing from most listings. A hang tag that says IPX8 in large type and nothing else is a marketing statement, not a specification.

• The grade, written as IPX6, IPX7 or IPX8 rather than as an adjective such as stormproof.
• The standard, normally IEC 60529, and whether the sample was sprayed, jetted or immersed.
• The configuration: number of folds used, orientation in the tank, and whether hardware was fitted.
• The source: an accredited laboratory name, or a clear statement of the internal protocol used.
• A depth and duration figure for anything above IPX7, because IPX8 has no default definition.

Where a brand publishes an accredited result, ask for the report number. Where it does not, run the field version of the test yourself: seal the bag with three folds, submerge it in a bath for thirty seconds, and open it over a dry towel. That thirty-second check reproduces most of what an IPX7 pass actually demonstrates for a soft bag, and it takes less time than reading the listing. The home testing guide gives the full procedure.

Laboratory immersion against the bath test at home

A thirty-second bath test and a thirty-minute laboratory immersion are not measuring the same thing, and it is worth being precise about what the home version proves. The laboratory test controls depth, orientation, temperature, water chemistry and sample conditioning, and it records all of them. The bath test controls none of those, and a bag 200 mm under the surface in a domestic tub sees about 2 kPa rather than the 10 kPa of a proper IPX7 rig.

What the home test does prove is the thing most likely to be wrong: whether the closure is clean, flat and correctly folded on that particular day. Almost every leak reported on a bag that passed its production test is a closure event, not a material failure, and a closure event shows up in thirty seconds. Use the laboratory number to choose a product and the bath test to maintain one.

If you want to go further at home, add weight to the bag so it sits fully under, use a ruler to hold the top 150 mm below the surface, and run it for five minutes rather than thirty seconds. That approximates IPX7 closely enough to catch any bag that is marginal, and it costs one bath towel and a kettle of water.

Matching a grade to the exposure you actually face

The right rating is the one that covers the worst credible event, not the best one. A commuter walking 800 metres in rain needs IPX4 and gains nothing from IPX7. A sea kayaker who might capsize and be towed needs IPX7, because a wet exit is a genuine immersion event. A whitewater rafter needs IPX6 plus redundancy, because the exposure is continuous jetting rather than immersion.

The one case where the grade is the wrong tool entirely is a bag that will be dragged underwater. A dry bag towed behind a boat at 2 metres for ten minutes is outside every rating a roll-top can honestly claim, and the correct response is not a higher number but a different product: a rigid case, or a dry bag used as an inner liner inside a rigid container. Ratings describe protection, not invulnerability.

There is also a safety boundary worth stating plainly. A bag that passes IPX7 is not a buoyancy aid. A sealed dry bag with trapped air floats, but the air escapes if the closure is disturbed, and no rating test covers that. If flotation matters, use a product designed for it; our floating dry bag range is built around that requirement rather than around an ingress grade.

Writing the waterproof requirement into a specification

For anyone specifying bags for a fleet, a retail range or a club, the requirement has to be written as a testable clause. Name the grade, name the standard, state the sample configuration and the number of folds, state whether the test is on the finished product or on a fabric coupon, and set an acceptance number across a production run. Vague clauses produce inconsistent product.

1. Name the grade and the standard: IPX7 to IEC 60529, immersion at 1 metre for 30 minutes.
2. State the configuration: three closure folds, buckle clipped, hardware fitted, sample upright.
3. State the sample size and pass criterion: for example 5 pieces per 500, zero permitted failures.
4. Add a second test that locates leaks: air inflation at 10 kPa held for 5 minutes.
5. Add an abrasion or flex preconditioning step if the bag will meet sand or a frame.
6. Require the report number and the laboratory name on every production batch.
7. Require a retained-grade retest after 1,000 hours of accelerated UV exposure.

Test methods for the supporting clauses are published by the same bodies that maintain the ingress standard, and the ISO catalogue covers the conditioning and sampling procedures most programmes reference. Two authorities, IEC for the code itself and ISO for the conditioning, is usually enough to write a clause that a production partner cannot interpret three different ways.

On our own line, waterproof bags have been produced since 2014 in an SGS-verified 4,950 m2 facility with 149 machines across seven production lines, and immersion testing runs alongside AQL 2.5 inspection on every bulk order. For the narrower question of which grade to choose, the IPX6 against IPX7 comparison and the immersion testing notes go deeper.

One closing point on honesty. A dry bag that is sold as IPX6 and behaves as IPX6 is a better product than one sold as IPX8 with an unsupported number, because the first can be trusted in the conditions it was designed for. Ratings exist to make comparison possible, and comparison only works when the number describes a test that was actually run.