Why is the Waterproof Rating Important for Rain Jackets?

Question

I have come across rain jackets with varying waterproof ratings. Why is this rating significant and what should I be on the lookout for?

Answer 1

The waterproof rating, which is usually written in mm and measures the force of water on the fabric, is the measure of how porous a fabric is. To be considered waterproof, a garment must have a rating of at least 1500 mm. That said, when hiking or backpacking, one is better off with a higher score. Light rain jackets start at a 5,000 mm rating, moderate conditions are covered by a 10,000 mm rating, while a good heavy rain jacket will be rated around 15,000 mm. Such regions as the Pacific Northwest should use jackets of no less than 20,000 mm rating. Hence with the increase in rating, the waterproofing features of the jacket increases.

Comments

Please review some paramo jackets. They do not have a waterproof rating, but it is because the waterproof rating system doesn’t make sense for their method of keeping you dry. It is not a membrane style system and it is supposedly completely breathable and keeps you totally dry without trapping in heat and moisture like membranes do.

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Gore (with a vested interest) is the company who makes the waterproof "standard" for rain jackets

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Wait that is not how it works, that hydrostatic pressure and in what type of rain you can thus wear it doesn't correlate.

Hydrostatic head is exactly what it says. A pressure.
The mm is a column of water set on a fabric.
Given that rain doesn't really increase above a certain pressure, and this is quite low. Like, can you imagine a column of 10000 mm on top of your jacket?
A backpack is something that can make you consider a higher hydrastatic head because your backpack pushes the water through.

Go check tent floors hydrastatic head and then think that your body weight pushes on it and there can be water underneath it.

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hard disagree on the last ive used the torrent shell 3L and id have to wholeheartedly disagree. my brand new jacket wet out on a light rain in southern california, unbelievably disappointed. if i took it where i live in the tropics im sure it would be even worse.  i bought an arcteryx beta ar after and have had 0 issues with it. so waterproof that i can stand under a waterfall and be dry.

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Hydrostatic head is a nonsense metric. Rain isn't high pressure. Even here in Scotland.

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This content: you need a bajillion mm hydrostatic head to survive the PNW! Spend $200 for your 1 pound jacket or you’ll die!

Every PCT hiker: yeah this is my trusty Frogg Togg. Cost me $25 and weighs 5 ounces.