Starting the process of building my 1st cache- a question of waterproofing

[+unforbiddenplaces]

I'm excited to place my first geocache!  I have 23 finds and counting, I've been researching obsessively and i passed the geocache hiders quiz on the 1st go with 8/8, and frankly i think i have a natural intuition for where a cache would appropriately go, so i think i'm ready to put together a simple traditional cache.  I want the experience of maintaining a straightforward 1.5 / 1.5 before i try to assemble a more complicated gadget cache etc.  I don't wanna put some old film container in a fence post though- more daring than that!

 

I'm starting the long process of confirming a placement for it.  I have my eye on a certain historical area nearby, which will have an area with some metal pipes outside.  I got some supplies to experiment with- a 2" PVC threaded plug and PVC threaded cap.  They fit together like a glove and create a nice sturdy small size cache that looks industrial- just big enough for a logbook, tiny pencil and 3 or 4 small trinkets.  I gorilla glued 2 strong magnet disks to the back so i can attach it to a metal surface.  My intention is to buy some rustoleum metal finish and spraypaint the outside to match the metal of wherever I wind up placing it.  Since i haven't gotten the location confirmed yet, i haven't bought the spray paint; i figured if my first location doesn't work out, it's a versatile enough idea that i can take it elsewhere changing only the camouflage.  At first glance nobody will notice it, but any slightly experienced geocacher will immediately detect what's out of place.

 

My question is this.  When i screw the cap down onto the plug, it doesn't thread all the way to the top interior of the cap, but about four threads up (as demonstrated in the 2nd pic). I figured this out by rubbing felt pen ink into the ends of the threads on the plug and screwing it into the cap to see where the ink ends when it's closed all the way.  It closes so tight and seamlessly that i don't think the lack of a rubber ring would keep it from being waterproof, but the fact stands that i can't put a rubber seal in place the way it closes now.  Do you think i should paint flex-seal in where the plug threads end, just to be sure, or would that be a waste of time and maybe a mess?  I haven't worked with PVC pipes/joints etc before and I'm betting they're supposed to screw airtight but maybe a professional knows better than me.

 

Any other suggestions or commentary welcome!

[+kunarion]

16 minutes ago, unforbiddenplaces said:

 It closes so tight and seamlessly that i don't think the lack of a rubber ring would keep it from being waterproof, but the fact stands that i can't put a rubber seal in place the way it closes now.

 

It's amazing how so much water can get in through a threaded PVC pipe cap.  I almost always find those things with standing water.  The threads also hold water, so the contents can get wet each time the pipe is unscrewed.  Maybe because it's attached to something magnetic, you can place it where it's more protected from weather.

 

Some people use rubber discs cut to fit inside a jar cap, where there isn't a built-in compression seal.  Could you stack discs of rubber somehow to form a seal inside the cap?

 

And keep an eye on those glued magnets.  Rather than just "glue", I've been using combinations of outdoor glue and mechanical attachment (such as quality duct tape to hold the magnets, or bolting the magnets to a container).  Otherwise, they come loose much sooner than I'd hope.

 

Good luck!

 

 

Edited June 18, 2019 by kunarion

[+unforbiddenplaces]

Thank you!  I thought maybe i was being overly cautious, i'm glad to know it's a common problem.

I don't know if it would be practical to stack rubber rings on the inside, if the thickness of one of those rings is about one of the pvc threads, i count a stack of ten, which seems like it would just fold inward.. or ten full discs instead of rings, which would reduce the inside space of the cache by at least half.

 

..hm i wonder if i shouldn't try to just find a sleeve of some kind of rubber material (like on a beer coozy?) that fits real snug around the plug and flex seal it into the OUTSIDE threaded area between the bottom of the cap and the base?  it only shows a width of about 5 threads, if i make it just a little wider than that it'll make a spring-snug seal.  is it a good theory?  i wonder if i could find such a sleeve of material that would be the right tightness.

Edited June 18, 2019 by unforbiddenplaces
attached photo

[+cerberus1]

4 hours ago, unforbiddenplaces said:

Any other suggestions or commentary welcome!

 

Have you found any of these things yourself yet ?  

Like kunarion, most we found sorta dry were in areas that (we felt) presented other issues.   Pipe bombs and bridges is one...

One of the first "caches" we tested in the back yard were different plastic pipes and connectors.  

We never really figured a way to keep anything with any threaded connectors dry inside.  

Cherne gripper pipe plugs didn't work either.  I bought a box of them I'll never use in 1 1/2" (figured folks would steal them for "other" caches).

 -  In testing , add in humans (relatives like to help :-) are opening/closing it in various weather conditions,  and either closing it too loose, or so tight that no one can open it.   Then someone eventually chips the threads... 

Be sure of your location too. 

Someone spots what may look like (maybe even to them-only) as a pipe bomb, and innocent as you feel it looks,  you got some splainin' to do. 

[+niraD]

I haven't built a PVC cache myself, but my experience with the ones I've found has been that they're either too tight and therefore very hard to open, or too loose and therefore not sealed.

 

There's a design I've seen for an underwater cache that uses a ball valve at one end, and a cap at the other, and glues both the ball valve and the cap to the pipe that forms the outer container. Then a smaller container (like a jumbo Bison tube or a preform) is placed inside the PVC container to hold the log.

 

And I've had some luck replacing a broken drain valve on a camping cooler with PVC parts. I used O-ring shaped rubber washers (designed for garden hoses, IIRC) to seal things. But I didn't glue anything together, and I sometimes have problems with the cap being tightened too much, and then the whole assembly comes apart when I try to take the cap off. (Before our next camping trip, I should put the rest of it together with PVC cement.)

[+kunarion]

3 hours ago, unforbiddenplaces said:

..hm i wonder if i shouldn't try to just find a sleeve of some kind of rubber material (like on a beer coozy?) that fits real snug around the plug and flex seal it into the OUTSIDE threaded area between the bottom of the cap and the base?  it only shows a width of about 5 threads, if i make it just a little wider than that it'll make a spring-snug seal.  is it a good theory?  i wonder if i could find such a sleeve of material that would be the right tightness.

 

As cerberus1 mentioned, one challenge is making an urban "PVC pipe" (or pretty much any container) look NOT like a suspicious device.  I re-worked a couple of my city caches so they had no "wires sticking out of them" (originally they'd hang by wire loops).  I just think of the poor fool who is seen "sticking a bomb to an electrical box", and what would be written of an incident if it were to become a news article.  And when it's someone like me who "looks suspicious" to start with .  All that's needed is a slightly elevated security alert in the area, when I didn't know about that.  Anyway, very much depending on the placement, the container's final "look" can be a challenge.

 

Have you found a "Nano" cache?  They're some of the smallest containers, typically impossible to find.  Your current design is almost a "big" Nano tube!  Just round off the points, form a huge "o-Ring" of black silicone RTV sealant around the exposed threads, paint the whole thing black and …it's a "Nano"!  Plus, maybe the RTV solves your water seal problem.  Just an idea.

 

 

 

 

Edited June 18, 2019 by kunarion

[+colleda]

As you mentioned watertightness I assume it will be exposed to the elements. When you have settled on a design (prototype) run it through several dishwasher cycles to see how well it seals. Don't forget to put a dummy log sheet inside it.

[+kunarion]

16 hours ago, unforbiddenplaces said:

I got some supplies to experiment with- a 2" PVC threaded plug and PVC threaded cap.  They fit together like a glove and create a nice sturdy small size cache that looks industrial- just big enough for a logbook, tiny pencil and 3 or 4 small trinkets.

 

It seems like your project is coming along well.  But another idea is to start with a watertight container that's already proven as suitable as a Geocache, then decorating that.  In the picture below, there's a Nalgene bottle, to which you might somehow securely attach a "pipe cap" to either end so it blends with other pipes.  Then there's a fake sprinkler head key-hider that I painted silver.  It has an o-Ring, and I bought a pack of additional o-Rings.  That one could have an attached magnet and hide well on most any metal object, especially plumbing.  The magnets in the picture are the mechanical attachment kind.  I glue or seal them as well as bolt them onto a container.  Too many times I've seen magnets fall off a plastic container in a  catastrophic failure (due to many factors), and when the magnets are the only way to hide it, I'm not gonna risk them falling off.

 

 

 

Edited June 18, 2019 by kunarion

[+Joe_L]

PVC threaded fittings are tapered, so after several rotations, the fitting is “tight” and can’t get much tighter.  One cannot keep turning it snug like nut and bolt. 

As stated by others, it is difficult to keep these connections dry.  I would try the thick o-ring around the threaded part approach.  Maybe a flexible rubber pipe coupling trimmed to length?

If the proposed location is under a bridge, it may not be exposed to any rain or snow and will stay very dry. 

I don’t recommend putting PVC in the dishwasher since the heat may affect the PVC; it could deform a bit.  (For real PVC piping uses, 140 degrees F is the maximum.)    

I have a cache held by a magnet under a bridge.  I used a blob of two-part epoxy glue to hold the magnet to the irregularly shaped container (match case).

 

Joe

Edited June 19, 2019 by Joe_L
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[+colleda]

If you can get hold of rare earth magnets use them and glue them inside the container. I use magnets salvaged from old computer hard drives, they are super strong!