How Water Proof Is An Ammo Can?

[+dino_hunters]

I'm thinking of putting a geocache underwater, in a shallow river bed. Any idea if an ammo can will keep out the water for a while, or should I get something more waterproof than that?

[+CYBret]

It really depends on the ammo box. But from what I've seen I wouldn't bet on it working very well. I've encountered two ammo boxes in the last couple months that had water inside of them.

 

One solution might be to put another box within the ammo box. That could help.

 

One other thing to consider, do you have any idea how much weight it will take to sink an ammo box? I seem to recall ClayJar having a post about that some years ago.

 

Bret

[jdoe]

Ammo boxes, new ones at least with a proper gasket will be waterproof. The question is how waterproof will they remain after repeated use (opening and closing). Eventually gaskets will wear out and the container will allow water to seep in. If you are set on immersing an ammo box, be sure you tell folks not to put items that won't survive in water and use a WriteRight log box and be sure to place that into a water proof container as well.

[CoyoteRed]

One of the problems any cache encounters is the human element. Caches on shore can have a water problem when folks don't close it or refuse to protect the cache while trading in the rain.

 

At the very least, I would provide clear instructions to not open while the cache is still dripping with water, open it upright, make sure the seal is clear of debris, trinkets, baggies, and other foreign matter when closing. Then I would baggie everything in freezer bags and leave instructions to close the bags.

 

Side note: it escapes me why folks refuse to close baggies when clearly the reason they are there is to protect the contents.

 

A good ammo can is very waterproof. I've received cans that had gotten water in them when the troops were using it and had been sealed ever since then. Somehow the water causes a vacuum and you will play hell opening one. If you have the chance, always inspect the seal before purchase.

 

As for sinking one, I seem to remember the size of a regular ammo can is something like 3x7x11 which would mean it would need to weigh greater than 8.4 pounds to sink. Multiply the dimensions in inches with 0.036127 to get the weight of the water it will displace. If it weighs less that water it displaces, it will float.

 

Of course, the greater the weight beyond neutral buoyant the greater resistance to moving along the bottom, too. Might want to tether it just in case.

 

Hope this helps.

[+the hermit crabs]

In this recent thread, Jamie Z posted a link about ammo cans in water that's worth checking out.

[adampierson]

A good ammo can is very waterproof. I've received cans that had gotten water in them when the troops were using it and had been sealed ever since then. Somehow the water causes a vacuum and you will play hell opening one. If you have the chance, always inspect the seal before purchase.

 

The vacuum you mention is a living example of the Ideal Gas Law. P*V=n*R*T

 

Basically when the container is closed, it is done so in open air. But once closed and immersed into water, the temperature inside the ammo box begins to drop due to the surrounding colder environment under water, and since the gasket seals the container from the outside world, a partial vacuum is created. The volume of the container remains the same, as does the number of particles inside the box, (R is the a gas constant). Since the temperature is reduced the only thing left for the gas to is slow down and contract. And that is where the vacuum comes from.

 

That is why some special containers (Pelican Boxes) have a built pressure release valve.

[+Tonsil]

It wouldn't hurt to touch up the paint on the can (many have rust when you get 'em), and tether it in case of flooding, etc. I have a can that survived being in a creek bed during a major flood. Everything remained dry inside, but it could probably use a new coat of paint.

[+MariettaGecko]

Also note that, particularly if you live in a humid environ, upon sinking the box in the body of water, the next cacher will probably find the box to be wet upon retrieval EVEN THOUGH THE SEAL IS PERFECTLY INTACT. why? Condensation. The very humid air that enters the box while it is open will go under water, the air will cool, and upon reaching the dew point, the water will have to condense on something. Since there's something there to condense upon, it will condense, and thus the inside of the box will get at least damp, depending on the dew point and humidity outside and the water temperature surrounding it.

[+Hunt]

You also might want to consider having the ammo can for protection from the river only. Drilling holes in it a few places and giving it a good primer coat and have a smaller and more watter proof container for a log book or whatever and have the log book in a plastic bag as well to fight the condensation that will form. and then all the things that don' t fit in the water tight container should be immersible objects. that away the ammo can can keep the river from beating up the plastic container and the container beeing disloged. and some one also mentioned the dificulty of submersing a water tight can. well the advantage of haveing the ammo can with holed is you cna place rocks in there or a non-corosive metal in the amo can so that the water proof container wont float away. Just a thought

[+sbell111]

Ammo cans can work very well under water.

[WH]

Ive got an underwater cache that uses an ammo can. Its been out just over a year and the inside is still dry as a bone,

[Dale_Lynn]

Don't count on me finding a "water cache" I don't particularly like the idea.... To many good places to place a dry land cache, just putting it under water shows a lack if imagination...

 

Dale

[CoyoteRed]

... just putting it under water shows a lack if imagination...

Personally, I don't care if a cache is imaginative. Take me on an adventure and I'm happy.

[+briansnat]

Personally I wouldn't rely on any container to keep an underwater cache dry. Seals can deteoriate, foreign objects can get caught in the seal and compromise them, or finders can neglect to seal them properly.

 

To ensure that the cache stays in decent condition, use waterproof paper for your logbook and if you are placing trade items inside, make sure they are things that won't be ruined by water.

 

Another option is to place the actual cache on dry land and put the coordinates for it underwater. Here is a good example of that.

Edited April 26, 2005 by briansnat