Waterproof?


Let me say right off that all major brands make tents that don’t leak. It’s
not negotiable for any of them. So please keep that in mind when you read about such-and-such a feature that implies more waterproofness *cough* bathtub floors *cough* when, in fact, you should experience no difference in the waterproof performance of the tent. Not one reputable brand will knowingly sell you a tent that leaks; not through thick and thin; not through hell and high water; and I mean actual high water. I’ve seen letters from people who woke up with the tent floor acting like a waterbed because the lake next to them had risen. They were completely dry and the specs were a taped, seamed floor made of fabric only 1500mm waterproof. How can one thing be more waterproof than another thing if they both don’t leak? Enough said?

Before taped seams you had to go to great lengths to seam seal everything — and those herculean efforts still leaked half the time. But now the seams are literally the most waterproof part of any tent. That's something that takes time to soak in (ahem) because there are a ton of "arguments" out there about more and less waterproofness and for US they're really all FUD and nonsense for all practical purposes.
But really, how trustworthy are manufacturers? If only there was someone who could check this behind the scenes. Someone who has relationships with many companies' design departments. Oh wait, that's me. And I've asked many repair/service departments about this (including, of course, "my" repair/service department during the 16 years I spent as Kelty's designer). I'm happy to report that it's quite rare for a tent to actually leak without being damaged (usually by animals). 

“Pseudo-Leaking” and Condensation on the other hand, is common and often inevitable due to high humidity conditions. If your tent has sags or has water collection spots in the rainfly, drips inside will definitely be a problem. That's another reason why MoonLights use polyester fabrics and we’re so concerned about sags. Vents in the  rainfly can, however, be a great help so the MoonLights have 2 or 4 vents, depending on size. Condensation can be so bad it REALLY makes it look like the tent is leaking – that’s why I call it pseudo-leaking. A great example comes in winter when tent floors are usually covered by a thin film of glistening wetness. I routinely carried a small sponge...but the floor was not letting water through it at all. It was entirely moisture from our breath condensing on the walls.

This brings up an important point: there are conditions where nothing can prevent condensation inside a tent. I was reminded of this on a recent rafting trip: we were camped at the bottom of a narrow canyon, right next to a large river, in cool weather. Man oh man was the dew heavy every night. And because the air was supersaturated with water, the condensation on the underside of the rainfly was equally heavy. Increasing the ventilation by leaving the vestibule doors partly open would have probably made the condensation inside even worse. Only running an actual dehumidifier inside the tent could have helped us. Still, because of the nice tight rainfly pitch, with no sagging even once, none of the condensation on the inside of the rainfly dripped on the inner tent or us.

Other camping styles in the world - especially in the UK and Europe - beg to differ on how waterproof a tent needs to be before it's considered waterproof. I can't authoritatively speak to their experiences but it does rain a lot there, sites are often designated and heavily used for extended periods, so maybe it's hard to avoid camping in a puddle. Plus, almost everyones' experience is based on nylon fabrics which shrink and grow, possibly hurting the coatings over time. For whatever reason, those markets insist on 5000mm waterproof coated floors or more and they carry heavier tents as a result. But here in the US it's very common to break camp and find that the driest spot in the whole area is where the tent was. 

Even 1200mm coatings are now being used by a number of reputable US manufacturers so that too, is probably just fine (with perhaps some limits or specific caveats). Remember, umbrellas do great and they're uncoated. 

MoonLights will have 1500-2000mm sil/pu• coatings on the rainfly and 2000-3000mm sil/pu coatings on the floor. I'm happy enough to let the floor coating be a little beefy - it's only a few square yards and people can be hard on a floor. The rainfly is definitely overkill but if we spec it too low, it might come in with occasional pinholes and we don’t want that no matter what the test method says.

•The term “sil/pu” means that one side has a polyurethane coating (so it can be taped) and the other side has an extremely water repellant silicone impregnation.


Trying to make sense of Europe and the UK’s ultrahigh waterproofness ratings


I’ll just jump right in (shocking, right): I think the overall amount of rain in Europe and in the UK especially has led everyone there to get paranoid about leaking. That’s fine and understandable as a precaution but I see manufacturers' talk of bathtub floors and less seams, for instance, with no acknowledgement that a taped seam is demonstrably the most waterproof part of any tent – a fact which makes the whole discussion irrelevant. And I see just monstrously high hydrostatic head waterproofness requirements that start at 5000mm and go up to 10,000mm and I've even heard of 20,000mm. It makes no sense. They're asking for tent floors (and sometimes rainflies) to be waterproof down to scuba diving depths. Where on earth are they supposing those kinds of pressures are coming from? Under most pads we're talking about a few fractions of a psi at most.

So I think that fear and a sort of waterproofness arms race are responsible for the super high waterproofness numbers. In the US it seems that all this has been tempered by a drier climate overall and a determination long ago that 1500mm was all the waterproofness any tent needed (by Natick, I believe).

And, of course there's water vapor condensing under a pad that might make one think that the tent is leaking. Leaking in an odd, no-puddle kind of way but still maybe that's the thought. Tent floors are not necessarily water
vapor proof - they breath a little. So maybe that's what's going on – another manifestation of pseudo-leaking.

Hey how about this: maybe a super-thick coating is supposed to prevent little pinholes. The tear strength goes in the toilet, but maybe that's it. Sorta like putting down a throw-rug. Hard to believe it would actually prevent pinholes but even the comforting thought might be the thing UK manufacturer's are looking for. Might be the solace customers are looking for. OMG it's heavy and bulky though


A Test You Can Do

Take a yard of fabric, make a pocket, and pour in about a half gallon of water - 2 liters - twist the top closed and continue twisting to pressurize the ball of water. If the fabric takes balloon-popping amounts of pressure without leaking, you have yourself a nice and waterproof material. If the ball starts spraying or dripping water, it's not trustworthy. (Note: The few tests I've done on fabrics with 1200mm waterproofness did not provide confidence inspiring results.)