What does waterproof mean?

[Sean P]

i was perusing a Rab  jacket on Massdrop recently and it was described as 10000/30000 – that is 10000 waterproof and 30000 moisture transfer.

now, I looked at reviews of the jacket and the users all described it as waterproof in heavy rain  but added ‘I wouldn’t trust it in a storm’ or ‘for multi days I would take a proper storm shell’.

so is it waterproof or not? I get that the 10000 figure is a measure of pressure resistance so unless water is forced through the membrane by packstraps, for example, (which it purportedly does not) how is it possible for this jacket to be less waterproof than a ‘proper’ shell?  If it is waterproof on day 1 why would it not be waterproof on day 5?

clearly DWR is a variable but that just affects vapour transfer, not waterproof ness.  I also get that waterproofness is also a variable on construction (hood, cuff design etc) but all things being equal what makes a jacket ‘more’ waterproof (a redundant term if ever I have heard one) than another if they have membranes rated for rain pressure?

[James Marco]

Read thru Richard Nisley’s posts. He has pretty good info on that.

Basically it has to do with wet-out, moisture absorption and water pressure. Often, DWR fabrics will maintain water resistance for some period of time at some pressure level. In a heavy storm, for example, the water pressure of a single droplet of water can be compounded by another droplet of water, the weave of the cloth, and how much water is already on it…they leak. In a light mist, with little impact pressure, these perform pretty well. As you mentioned, under shoulder straps can be a real problem, though. Water vapour can be a problem if one surface is covered with water. It has no choice but to penetrate inside (not quite true since poly films also leak water vapour, but a way of thinking about it.)

Contact, like the old cotton canvas tents, is bad. Try to avoid touching your jacket…

I don’t buy DWR stuff. When I want water proof items, I want 5000mm resistance or more to water. Yes, I give up some ventilation for that. IFF it has been raining for half a day (around four hours of fairly steady rain) I always get wet to some degree. Either from sweat (no ventilation) or from water running down my legs and into my shirt (by capillary action exacerbated by movement.) There is no such thing as remaining dry in a long rain storm unless it is also cold…usually this means ice and snow.

Over time, a DWR will wet-out. Sine it relies on water repulsion, this can be bad after a day in the rain. It never has a chance to dry out and regenerate (you can think of it this way.) In the ADK’s, when we get storms, it is usually a matter of a couple or three days. DWR’s fail spectacularly. No more than a wind shirt. At least a 5000mm vinyl coated nylon will still repel most of the water, easily. And, it doubles as a ground cloth. They are cheap enough (I think I paid $29 for my last Xlarge jacket 4-5 years ago) that I can replace it if it gets ruined. It is fairly durable though. Mostly, I have lost them through bushwhacking, tearing them, not because they started leaking.

[Jerry Adams]

The combination  of membrane and DWR makes it more “waterproof”

Some people like it, some don’t, it’s not perfect, depends on weather,…

Totally waterproof – more sweat condenses inside.  Umbrella works if it’s not too windy.  Windshirt works good if it’s not raining a lot.

I prefer membrane/DWR

[Brett Peugh]

I only own two things that are waterproof.  An OR Rampart rain suit with the torso-flo for it to vent and a poncho/tarp.  Only things that after 5 years that still have remained waterproof.  If it is a light rain, an R2 will do me.

[Todd T]

All the industry terminology is a dance to loosen your wallet.  If it’s described as breathable or as having/needing DWR, it’s either not waterproof or won’t be for long.  (Cynical perhaps, but based on drenched experience.)

[Dale Wambaugh]

There is a good guide with a chart of specifications on waterproof/breathability for a number of brands at https://www.sierratradingpost.com/lp2/waterproof-guide/. 10,000mm waterproofing isn’t exactly stellar.

I’ve always been suspect of waterproof stretch fabrics. Asking a thin membrane to perform when bonded to a stretchy base seems risky. I tend to wear my rain shells on the large side for layering and “bellows effect,’ so stretch isn’t something I’m looking for anyway.

 

 

[Ryan Jordan]

If it can be assumed that seam taping, zippers, closures, and DWR are not part of the equation here, then ocean fishermen probably have the only claim to waterproof: 0.5mm PVC – like the kind they wear in those snazzy yellow bibs and long jackets. PVC coatings on fabrics have hydrostatic head resistance in the range of 100,000 mm.

That’s generally 3-10X higher than what we see in “waterproof-breathable” fabrics.

100,000 mm is a LOT of pressure.

Water can be pushed through a 10,000 mm textile by kneeling, sitting, or maybe the pressure of pack straps with a heavy load.

And water can wick/seep (whatever you want to call the capillary movement of it) through 2k-30k membranes if they are wetted out with moderate pressure. But when this happens, that also means that the pores of the membrane are full of water and the fabric can’t breathe, so moisture accumulates on the inside of the fabric as well – these processes are very difficult to sort out – which one is dominant in a wetted out jacket?

The only “really waterproof” (!) “breathable” jacket/pant combo I’ve personally tested is a set made from the newest version of Gore-Tex Pro. I actually had a very difficult time getting that fabric to fail through the normal pressures of carrying a heavy pack, and kneeling on mushy ground. It seemed as breathable as any other “waterproof-breathable” jacket, which was “not a lot” but certainly noticeably better than fabrics from a decade ago.

But that jacket has a weight of 18 oz, so … seems a bit out of the range of “light” for many of us. Also, GTPro jackets are enormously expensive, especially those that are well-made (bird).

Like anything else, I try to look at “waterproof-breathable” on a continuum of performance, and match what sort of performance I’d like to have to the conditions I expect, and then search for the piece of gear that accomplishes that at minimum weight.

[Jeffs Eleven]

“Like anything else, I try to look at “waterproof-breathable” on a continuum of performance, and match what sort of performance I’d like to have to the conditions I expect, and then search for the piece of gear that accomplishes that at minimum weight.”

Preach it!!

Should be posted all over every store and brand that sells WPB gear.  (I guess its up to the salesperson to teach… but first, they must understand)

[Dale Wambaugh]

My poncho doesn’t have strap pressure issues and is well ventilated :)

[Sean P]

Thanks for the info.  I suppose my question really relates to the hypothesis that, DWR aside, the capacity of a membrane to resist moisture should be constant, for that membrane.  Once wetted out it shouldn’t matter whether it’s day 1 or day 5 of a walk.

I am just curious as to why a reviewer would favour gore tex, for example, over ()tex if they are both waterproof in the conditions experienced by the reviewer over 1 day’s worth of hiking -assuming wetting out on day 1, which is generally my experience in sustained rain.

 

 

[Dale Wambaugh]

Gore Tex products do tend to have better quality all-around and there can be some placebo effect too. It would be interesting to do double-blind testing with no logos on the gear.

I think it is very hard to tell if a jacket is leaking overall or if it sweat is condensing inside after a few days in the rain. Hike uphill for a few miles with a load in the rain at 50f and 90% humidity and tell me the difference! Identifying a point pressure issue vs condensation at the same point is a challenge.

The theory is that once the fabric wets out, the membrane can no longer breathe and you have an expensive plastic bag. A soaked shell is cold and heavy and just FEELS bad. Certainly a failed seam, a hole or delaminated membrane will be more obvious to identify a true leak.

[James Marco]

Well, I don’t know that much about water proof ratings at Sierra Trading Post. My old tent, for example, had a 10000mm floor in it. On day I set up in a dip because that was the only spot. It rained and sat in a 1.5 to 2″ mud puddle. Both my wife and I stayed dry, though, as well as our cloths/gear, despite crawling around and packing up stuff. My old vinyl clad jacket still keeps me fairly dry when hiking. ‘Corse my pants and eventually my shirt get wet, but it never leaked around my straps. I think this was only rated at 7000. Anyway, I agree with Ryan… there is a continuum of waterproofness. Only experience will tell you what you need based on the weather. A lot of it is the perception of warmth, even though it is wet. But that is another subject…

[Dale Wambaugh]

STP is simply listing the manufacturers’ published specs. There was a decent graphic description of rain fabric construction there too .

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