Water columns and breathability in ski jackets and pants explained

February 08, 2023
When you are looking for a ski jacket or ski pants, you frequently come across terms like “water column” and “breathability rating”, in combination with numbers like 5.000 or 10.000. What do these terms and numbers mean, and what do they tell you about the performance of your ski jacket and pants? Read it now!
Water columns and breathability in ski jackets and pants explained

What is a water column?

The water column (WC) is an indication of the waterproofness of your ski clothing. To be more exact, it states the pressure your ski jacket or pants can withstand before they get penetrated by water. Pressure is commonly measured in millibars or Pascal, but in the textile industry, it is stated in mmH20 (water column in millimetres). 

Why, you ask? Well, because waterproofness is measured by placing a long tube filled with water on the fabric – a test known as the hydrostatic head test. The higher the water column in the tube, the higher the water pressure, and thus the material’s waterproofness. For instance: if the tube is filled with 5.000 mm (5 metres) of water before it penetrates the material, the water column is 5.000 (often noted as 5K). All waterproof O’Neill snow gear has a rating of at least 10K


The difference between water-repellent, water-resistant and waterproof

In the context of outerwear, the terms waterproof,water-repellent and water-resistant are often mixed up. The thing is that they do not mean the same. Water-repellent is a general term that refers to clothing that is able to withstand (some) water. This means that both waterproof and water-resistant clothes can be called water-repellent. In general, water-resistant outdoor clothing offers a way lower level of water-repellancy than waterproof clothing. To be called water-resistant, a DWR coating suffices, while waterproof clothing offers serious protection against rain showers, and is more technical in terms of fabrics and coatings. 

What is the breathability rating of a jacket or pant?

The breathability rating expresses the amount of water vapour that can pass through your jacket or pants. Breathability is usually stated in g/m2/24hr. In other words: the amount of water, by weight, that can get through a square metre of fabric in 24 hours. This number is also known as the Moisture Vapour Transmission (MVT) rating. The higher the number, the better the breathability. Besides breathable fabric, a lot of performance snow jackets and pants also feature ventilating options to let warmth and moisture escape.

What is a good water column rating for ski clothing? 


3K waterproof rating

Waterproof ratings of ski jackets start at 3.000 mm. Nevertheless, ski clothing with a water column of 3K can only withstand a limited amount of water. These jackets and pants are great for spring days and some light drizzle, but won’t keep you dry in more demanding conditions.  

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5K waterproof rating

Clothing with a 5K waterproof rating blocks out some water, but isn’t able to withstand snow storms or heavy rain showers. Jackets and pants with a 5K waterproof rating are OK for exploring the resort or the park on nice days, but aren’t recommended when you head off-piste or when you are facing tough weather conditions 

10K waterproof rating

 A water column rating of 10K is the industry standard for  snow jackets and pants. It’s also the standard in O’Neill snow gear. Jackets and pants with 10K waterproofing will easily keep you dry on regular riding days. For the most demanding conditions, however, you can go for an even higher water column rating.

20K and above

When we get above 20.000 mm, we get into the high-performance realm. Most brands’ high-end lines boast water columns of 20K or above. Above 25K, not even a single drop of water will get in. Gore-Tex clothing, for instance, has a 28.000 mm water column rating and guarantees to keep you dry.

O'Neill Gore-tex skiwear

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Frequently asked questions

Why are waterproofness and breathability important?

Waterproofness is important to prevent snow, rain and water from seeping into your ski clothes. Breathability, on the other hand, allows sweat to evaporate and is crucial to keep you dry from the inside out. So while they might seem opposites of each other, waterproofness and breathability actually work together to keep you dry. Waterproofing and breathability often scale together as well. This has everything to do with the quality of the materials that are used. For instance, most jackets with a waterproof rate of 10K also have a breathability rate of 10K.

What is a good breathability rating for ski clothing?

As said before, the waterproof and breathability rating often go hand in hand. A breathability of 10K is the standard in the industry, and does a great job in letting sweat evaporate. Anything below 10K offers fairly little breathability – anything above is great when you are really working up a sweat.

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