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An underground, waterproof cache has many uses from prepper survival to an ingenious geocache to hiding a house key. PVC is a great inexpensive and fast way to hide something underground. It is also often done wrong. I'll walk you the process of getting it right the first time.

Step 1: Materials

Length of PVC pipe - diameter of your choosing
2 PVC Caps
1 Test plug (In PVC pipe section of the hardware store)
PVC cement

Tools:
Post hole digger
Digging bar
Saw if cutting pipe to length

Optional:
Automotive grease

Silica Gel (from craft store flower section) or Damp Rid refill

Sock or pantyhose.

Don't Buy a screw cap end plug

Step 2: Pop a Cap

Cut PVC pipe to desired length.

Using a liberal amount of PCV cement attach one cap to an end of your pipe.

Let the glue fully cure.

Step 3: Mitigate the Moisture

Unless you are in a desert the ground is a damp place. That temperature variance can cause condensation on the inside of your burial tube. Depending on what is packed and how you pack it you may seriously want to add an additional layer of moisture protection.

Silica gel can be purchased in bulk from online suppliers like amazon or in the flower section of craft stores. Silica gel will trap the excess moisture within itself and is a good solution for long term storage. Pour some in the pipe. If you are concerned it will get into the contents of your stored materials place it in a clean sock or piece of panty hose. Secure the sock or hose with a knot and a zip tie. Silica gel will continue to absorb moisture until it is saturated. It will not absorb any past that point. However it will seek humidity equilibrium. If the moisture content of the air drops below the moisture content of the silica gel the gel will release the moisture back into the air. This is why plant nurseries put it in their soil.

DampRid is a product that is sold to help pull moisture out of the air and trap as well. It is typically used in basements and campers. Much like silica gel packets. Unlike silica gel DampRid will continue to absorb moisture past the point of saturation. Once saturation occurs it will drip down. Place the damprid in a small canister with holes in the top. This will catch any weeping water.

Step 4: Plug It the Right Way

A test plug is a rubber gasket that has a wing nut and a washer. When you tighten the wing nut it pushes the rubber out to the PVC pipe creating an impermeable water barrier. Unlike the more expensive thread type pvc plugs the rubber test plug will not leak. Thread style plugs will allow small amounts of water to weak down the threads and into the contents of your cache.

Insert the contents into the tube and tighten the test plug.

Pro tips: If you are going for long term underground storage remove the wing nut and coat the threads with a liberal amount of automotive grease. This will keep the threads from rusting, corroding or freezing up. It will also allow you to remove the test plug a little easier when you come back to retrieve the contents.

Take your 2nd pipe cap and cover the test plug. This will keep water and dirt off the plug. This will help prevent damage and make the plug wing nut easier to use in the future.

Step 5: Drop It Like It Is Hot

Mark where you want to bury your cache. Make note of physical land marks. Dig the hole and drop in your newly assembled tube. Cover the hole and consider placing a rock, stone, paver, garden gnome, etc on top to make finding it easier for you in the future.

<p>Oh Man, I've made a few of these with screw off tops, but sometimes the screw top isn't quite air tight, and it's kind of expensive. This is a much better alternative in my opinion. Nice thinking.</p>
Amazing instructable A++
<p>Thank you for your kind words!</p>
<p>Yes You did get it right!</p><p>One add after I read all replies to date, warming everything going in the tube with a hair dryer, dry heat, can make a big difference too.</p><p>If you just got to, got to retrieve the items, think double the tubes, a tube, inside a tube. Oh, own the land!</p><p>I buried my first ? 12 ga shot gun when I went over seas in 1981. (Oil fields of Saudi Arabia) the Bolt action was worth at least 25$. When I got back home just 22 years later, the small water oak tree was about 30 inch in diameter. Two months to remember the gun, Two days to get it out from under the tree. I had greased all but the stock, wrapped that in a walnut oil soaked rugs, wrapped in visqueen (plastic sheeting). That was with 6 inch Sch 80 pipe. Capped both ends, never thought of You great idea of the plug. Looked smaller then what remembered... But it was in great condition.</p><p>- Big Jake</p>
This is awesome. Can't wait to try it. :-)
<p>Check out the updated photos and let us know how it goes!</p>
<p>I made these very same ones about 10 years ago to use as Geocaches and Terracaches. They worked great until somebody called one in as a pipe bomb. The park was evacuated and the cache was destroyed. (all the Geocache info printed on the outside means nothing) a couple of weeks later , different park, different cache, same result. Someone at the Rockford park district traced the caches to me and I was summoned to their offices. Long story short, the Rockford Park District nor the Winnebago County Forest Preserve District allow PVC pipe caches of any type. So if you are a cacher, please CHECK LOCAL REGULATIONS before making and using these</p>
The Holey-Moley Digger can be used to dig straight, uniform, deep 6&quot; to 8.5&quot; holes for cache tubes using a shop vac. Comes in do it yourself kit. Http:/www.holeymoleydigger.com
<p>The rules of geocaching prohibit burying , even partially, a cache.</p>
<p>Great! Probably works well with anything you would want to hide. Money, a survival kit, ammunition, ect. I would imagine that this would work with any diameter of pipe as long as you could get a dummy plug for it. For Geocaching, if you don't want to dig a hole, you could wrap it in camouflage duct tape, and hide it under a bush.</p>
<p>Good idea! I had the same one a few years back, was going to stash some money (now I'm broke so don't need it). Could enough moisture be trapped inside to cause a major problem? I never thought of that and was just going to use the cement that you regularly use...that's the way they do plumbing, right? Good job, yours looks much more sophisticated. </p>
<p>Gluing the two ends will be just fine - you just have to work a bit harder to get the contents out. Might be a good idea with cash - as long as you don't cut it in half!</p>
<p>DampRid turns to a liquid when it absorbs water. The last thing you want is a liquid soaking your valuables that doesn't evaporate. Get a silica gel pack (like what's used to keep gun safes dry) instead and drop it down there.</p><p>Also, why are you burying a map to your treasure that you're burying? ;) </p>
<p>The damp rid will absorb moisture past the point of saturation and then drip. So you are right it is better to keep it in a container. I updated with the photos of my silica gel.</p><p>As far as the map, well it is my system of redundancy...a hiding spot for my hiding spot. Just kidding. This tube is for the kids and it is burried in my wife's garden.</p>
<p>Thanks for the clarification!</p>
<p>This a great idea! Some of history's best inventions are simple yet so effective! You have my vote!</p>
<p>If you bump that up to 6&quot; pipe, you can store a bit of material. I've got several put away ;-)</p><p>If your tube is large enough, I suggest using plain old silica gel cat littler in a plastic container rather than damp rid. I use a mason jar with a screen instead of the lid's disc insert to seal the jar.</p><p>Also, if you're truly looking at extended storage, consider permanently gluing the ends shut. You can always remove an end with a handsaw (or a wire loop saw (DIY-plumbing aisle) ) when you retrieve it.</p>

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Bio: I'm a computer engineer - but please don't judge me by that. I heat with wood, fix broken things and love camping with my ... More »
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