On our recent trip to Mono Pass and Pioneer Basin, we had something happen that really took us by surprise. No, it wasn't the hailstorm that clobbered us right at dusk--although we had hoped we would miss that particular adventure. But it's related to that.
The next morning, when we got up and inspected the damage around our campsite from the hailstorm, we were surprised to see about a half an inch of water sloshing around inside our Bearvault.
Huh? The bear can was sitting away from our tent, in a small clearing among some trees, and it was upright the entire time---from before the storm hit to the next morning. So how did all that water get into the can?
All we can imagine is that the small lip on the bear can that sticks out beyond the lid was saturated during the rain and hailstorm, and that the can and its contents were relatively warm from the day's hike. As the contents cooled, they must have created a bit of a vacuum, and if the lip were saturated with water, maybe the vacuum sucked the water standing on the lip up through the threads and into the can. And that continued for some time, because the storm lasted a while, and the really cooled down everything--there was still an inch of hail on the ground when we woke up the next morning.
Loc: Washington State, King County
Do you have a relatively new model, or is it a number of years old? Some years ago (five? dunno ...), BV found that a particular bear had learned to pop the tops off of their cans and so changed to a deeper lid, one with more threads. With the top sitting flat on the ground, the old one was maybe an inch or less. The new one is (off the top of my head, I'm lazy this morning) perhaps a couple of inches thick.
I'm surprised to in either case, but even more surprised if it was the thicker (okay "taller") lid and it was screwed all the way down tight. And I assume when you say that the can was "upright" that means the lid was up.
I certainly have had water come into the black Garcia canister if left upright; with a Garcia, a person living in a rainy climate quickly learns to set it lid-down and/or wrap in plastic. For a BV, however --- not easy to get water past all of those plastic screw threads. Your explanation (significant change in air pressure from when you closed it) is as credible an idea as I can think of. You would think that you would know if there was a crack or a hole in the plastic!!
I don't fancy the "breathing moisture in" theory due to the sheer volume. I can agree with the concept, just not the amount. But how? Could the rain and wind have been heavy enough to directly drive the water upward, past the threads? I know we're not supposed to tighten the lid so it's left loose, and given enough time and direct rain and ground splash, combined with swirling wind I'll speculate that's what happened. (Note to self: carry second trashbag.)
One Bearikade plus--a gasket seal. (I own both FWIW).
I have had the same thing happen to me. I was camped at Crabtree Meadows in a hard rainstorm. I set my BV-450 out in an open area, upright and completely closed. When I got breakfast out of it the next morning there was about 1/4" of free water in the bottom of the canister. I couldn't explain it then and I can't explain it now. The way the lid on the BV is configured water would have had to flow uphill through the threads about 1-1\2" to enter the canister. I put a plastic bag over the BV now if it looks like rain.
I have also had water get into my Bearikade Weekender in rainstorms. It appears to get in around the fasteners and can do so in some quantity. Now, when I put the Weekender out I position it top down. It seems to work.
Loc: Washington State, King County
FWIW, the picture you posted is definitely of the newer lid, the taller/thicker one.
While I didn't think of those cans as truly waterproof, I would never have guessed that much water could get in just standing upright.
Perhaps the BV folks would respond if you contacted them. At a PCT gathering some years ago I met the president of the company and he struck me as a really nice guy. In particular, I had the old lid and he worked out with me to mail the new improved lid to my house. For free, and in time to get it to me by the time I needed it.
Sarah at BearVault was kind enough to respond to our recent questions about water getting into the BearVault during a storm. Here's what she wrote:
"There is a small lip on the BearVault housing which prevents a bear’s claw or tooth from getting under the lid during an attack. If the BearVault is almost perfectly upright then during a rain this lip can allow a small “moat” of water to form at the top of the housing. If the storm then passes during the night, the atmospheric pressure gets higher and this forces the water in the “moat” up the threads and into the housing.
To prevent this, just tilt the unit slightly during the night so that the water cannot accumulate in that “moat” if it rains- it’s that simple."