In-floor safe condensation

[Verado1250]

In my new shop I built last year, I made an in the floor safe, in concrete. This safe is 6" pvc with a screw on pvc cap on top, with a glue on cap at the bottom. This is covered by a locked 1/4" metal plate that is level with the top of the concrete. The pvc pipe is vertical and is 18" long. This is well concealed as a heavy piece of machinery is on top of it and I doubt anyone would ever think to look there. I haven't put anything in there yet, due to the inside walls of the pvc always being damp/wet. There is 1" gravel all around it and a 3/8" hole drilled in the bottom to allow drainage. I plan on keeping a few valuables in there as it's away from the house and virtually fire-proof if I can minimize the moisture. I have thought about keeping the valuables inside a zip-lock bag or Tupperware. Anyone have any ideas on how to eliminate the moisture? Thanks.

 

[BillK]

and a 3/8" hole drilled in the bottom to allow drainage.

That is what is causing the problem. It needs to be totally sealed.

 

[rkevins]

try to seal the hole with silicone and put a desiccant bag in it

 

[Verado1250]

Ok, I will give that a try. Thanks for the replies.

 

[NUTTSGT]

I was going to ask if you put the hole in the PVC before it was set in the ground or after trying to rectify the situation.


If it was prior, think about this, put a piece of plastic over some grass outside. Notice the moisture on the bottom side of the plastic, it plastic is keeping it from evaporating. You're basically doing the same thing, the moisture is coming out of the ground and can't escape.

I'd venture to say if you left it open overnight, the sides would be dry.

 

[fasteddie]

Find or cut a flat piece of PVC and glue it over the hole with PVC cement.

 

[Caman]

I’m also gonna say if you didn’t put some kind of thermal barrier between the pvc and ground you’re always going to have issues. The moment you open the safe it’s going to pull in humidity and it will condensate. The cooler the ground compared to the air temp the more condensation you will get. Spray foam coating the outside would have been a great idea.

 

[Verado1250]

Looking back now, I wish I had put a thermal barrier around it. The part of the shop where this is, the ground slopes, so I had to have a foundation that is approximately 7 ft. high, and it's filled with compacted rock. The pvc is a few feet from the sides of the foundation so I didn't think about this problem. I pre-drilled the hole before I set the pipe. I had to set the pipe when the concrete guys were not there, as I didn't want them knowing what it was. When they came out the next day, they asked what it was as only the top was showing and it was covered with duck tape. I just told them it was for dust collection. I will put some caulk around the hole and put a piece of pvc over it to see if it eliminates the problem. If not, I will try the Tupperware route. Thanks for the advice.

 

[mike93lx]

Once you seal it, either keep a dessicant in the tube or everything sealed in plastic

 

[cstmg8]

Does it have to be 6"? If you can stand to lose a little room, maybe put a 5" piece inside with insulation between the walls?

Sent from my Pixel 2 XL using Tapatalk

 

[Verado1250]

Does it have to be 6"? If you can stand to lose a little room, maybe put a 5" piece inside with insulation between the walls?

Sent from my Pixel 2 XL using Tapatalk

I may try that if the other solutions don't work. I'd rather keep it where it's at if I can. If I went to 5", I would have to have a screw on cap/coupling, etc., and that would be problematic I think fitting inside the current set-up.

 

[NUTTSGT]

I’m also gonna say if you didn’t put some kind of thermal barrier between the pvc and ground you’re always going to have issues. The moment you open the safe it’s going to pull in humidity and it will condensate. The cooler the ground compared to the air temp the more condensation you will get. Spray foam coating the outside would have been a great idea.

I really don't think there will be much of a problem. The PVC temperature should be consistent with the ground temp. It'll remain cool when you open the lid as the cooler air will stay in place. I would think it would be quite similar to a cold sump in an igloo.