Tips & Tricks_Waterproof vs. water repellent

Tips & Tricks: Waterproof vs. water repellent

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Waterproof jacket letting rain drops drip off.
Staying dry in the rain

Worst case scenario: It’s the second day of a two-week camping trip. Your backpack is stuffed with the necessary equipment and the only clothing you have with you is what you’ve got on your back. Extra clothes get left behind to save weight and space. But then, the weather takes a turn for the worse and doesn’t look like improving any time soon. The worst thing that can happen to you now is your clothes get wet. You have nothing to change into and you don’t know when you might get an opportunity to let things dry. You’ll have heard the annoying cliché that “there’s no such thing as bad weather, only inappropriate clothing”? Well, there’s a lot of truth in it. In a situation like this you need a good waterproof layer to protect you from the rain and the cold and of course the hotspots from rubbing rucksack straps and clothing. But how can you tell the difference between good and bad waterproof clothing? What will really keep you dry?

It all comes down to a standard

The standard is the way in which the water permeability of a fabric or a membrane is measured. Or simply put, the amount of water that can get through a fabric or a membrane within a certain amount of time.

The standard, called the Hydrostatic head, is tested by exposing the external face of the fabric to a column of water so that gravity forces the water through the material with a constant pressure. The time it takes for three drops of water to make their way through the fabric is measured. The height of the water column above the material before it leaked is measured in millimeters of water and forms the standard. Just remember the the higher the number the better.

As always, when standards are involved, things get complicated between countries. Here goes. For clothing the European standard DIN EN 343:2010-05 (protective clothing against rain) comes into play. According to this standard, a fabric with an 800 mm water column is rated as class 2 waterproof and from a water column of 1,300 mm a fabric is rated as class 3 waterproof. And since all of this just leads to confusion, Germany has its own rule of thumb. A fabric is considered waterproof if it has a water column of 1,500 mm or more. You can’t really go wrong with this rule.

Our friends from Switzerland, however, are a bit stricter. The Swiss Federal Laboratories for Materials Science and Technology (EMPA) in St. Gallen say, a fabric must have a water column of at least 4,000 mm to be considered waterproof. To each their own.

So how much of a water column do I need?

Alpinist laying in the snow.
Alpine tours have special demands on the material

As always, this depends on what you are planning to do and where? The question is, how much water will the fabric have to deal with? A decisive factor is whether or not pressure is to be applied to the material as well as water. Will you just be standing in the rain with your rain jacket or will there be strong wind hitting the jacket, as well? Will the straps of a heavy backpack also be applying pressure on the jacket and forcing water through the fabric?

This should give you some idea of the sorts of pressures we’re talking about: According to Wikipedia, sitting on wet ground is equivalent to a 2,000 mm water column. When squatting down, the pressure is equivalent to 4,800 mm. And of course the weight of the person also influences the pressure.

Still no closer to understanding?

In other words, the boundary between waterproof and water-repellent is a grey area and depends on several factors. Type of water exposure, duration of exposure, the water pressure on the fabric (caused by the wind, a backpack or the wearer).

But here’s the good news. All hardshell jackets are in fact waterproof. At least, all of the ones in our shop. Most manufacturers start at a water column of 10,000 mm, which means they are way above what the standard defines as waterproof. Most hardshell jackets can deal with 20,000 mm and some even get close to 30,000 mm.

But you should always keep in mind that it depends on what you are planning to do with the jacket (or trousers). And remember that these figures apply to new jackets. Used and worn fabrics and membranes quickly lose the properties they had when new.

Waterproofing your jacket on a regular basis is vital. Water will bead and roll straight off of a well-waterproofed jacket giving the wind no chance to force it through.

It’s also worth noting

The 3-layer-membrane Gore-tex Pro in a jacket.
Breathable but waterproof. The 3-layer-membrane Gore-tex Pro

that the water column only refers to the fabric itself. There are a number of other factors that influence the protective function of a jacket as a whole. If a front zip is of a low quality, for example, it may let water into the jacket, particularly in a strong headwind. Poorly-designed hoods are another factor that should not be ignored.

And the breathability of your jacket is extremely important of course. What use is a completely sealed jacket, that cannot transfer your sweat to the outside? Getting wet from the inside is no better than getting wet from the outside. Although, sweat is somewhat warmer than rain to start with.

As usual, you can always contact our experts from our customer service team if you have any questions. Our customer service is available during the week from 8 a.m. till 4 p.m. and can be reached by phone at 03 33 33 67058 or via e-mail.

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Alpinetrek-Expert Fritz

Alpinetrek-Expert Fritz

Climbing and mountaineering became my passions thanks to my fascination of the mountain world (and thanks to a few coincidences). And now, looking back on my now 25 or so years of climbing experience, I believe I owe a lot to mountains and climbing walls.
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  1. I have purchased your Mountain Equipment Odyssey rain pants with and advertised hydrostatic head of 20,000mm. However, when kneeling in wet grass, sitting on a wet bike saddle or sitting on wet grass, there’s definitely dampness coming through. I weigh 75kg and would expect the fabric to withstand far in excess of the above mentioned activities.
    I’m regularly treating the fabric with Nikwax products. Please advise. Cheers. Mattia

  2. Hi Mattia, I hear you’ve already been in touch with our Customer Service team – that said, you’re absolutely right. A hydrostatic head of 20,000 should happily keep out that kind of dampness with no problems whatsoever. Wet legs are no fun!

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