Underground Compressed Air

[zuiko]

I want to run a compressed air line in a trench, about 100 feet with three 90 degree bends (one in the trench and two to come out of the ground).

I am leaning towards copper since I am pretty confident of the solder joints not leaking... I'm much less confident in pasted up PVC joints. Do buried copper lines last or does it corrode when buried? I would be probably want to use the thinwall stuff because of cost.

Polyethelene pipe would also be an option and is very cheap but I don't know how good those barbed connections on the ends would be at holding air. They do make it in a 150psi version that would probably work.

Any suggestions?

 

[EddieWalker]

There was a big discusion on this topic not too long ago if you do a search. The concesus was stay away from plastic, it will shatter and could be very dangerous. Underground wont be as dangerous, but if it breaks, you still have to redo it.

Another concern for me wasn't so much for my saftey, but what if it explodes and somebody else is hurt. It's just not worth the risk of for saving a couple bucks.

Copper is the best and probably only way to do it correctly. I couldn't tell you if thin wall will work or not, but for a little extra, I'd buy the best I could find. Do a preasure test before you bury with soapy water and you'll find you leaks if you have any.

Good luck,
Eddie

 

[Inspector507]

Why not use the flexible copper in rolls? No joints except at either end, heavier wall may hold up under more pressure. Just a guess on that one though.

 

[chim]

I'm not a plumber, but I often pay attention to how they do things. For copper underground installations (at least for domestic water) they use flared fittings and not soldered. A plumber told me it was against the code to solder water lines for underground use.......................chim

 

[RonL]

zuiko

I'm also planning on running underground air lines. My intent is to run oversize PVC conduit and then run an air hose through it. If the air hose gives out I'll pull it out and pull a new one. The conduit will be vented by leaving the ends open.

RonL

 

[JacknCoke]

Another problem that I ran into with an underground line was that moisture collected in it. And after a year or two the line was full of water and we could never purge it all out. We ended up abandoning it and going with an over head line but this was only about a distance of about 25 feet. So overhead is probably not an option for you 100 feet distance. I would recommend biulding an underground box at the lowest end of the line and install a valve that you could open to drain any moisture out.

J.D.

 

[K_Daulby]

here is what i did about 5 years ago and i have had no problem.
I used black pipe and did about 150 feet of piping to do my whole 40x60 barn.
Then I wanted air to my house for many reasons. My house is 150 feet from my barn and i was runing electrical to my barn from house so i just went to a wholesaler and bought a length of high pressure air line, just like u would use if you conected a tool to your compressor. i just direct buried it. in the electrical line trench. i think i bought 200feet for $75 or $80 then i just put quick conects on the end of the high pressure hose and i have had no problems since. hope this helps
kevin /forums/images/graemlins/grin.gif

 

[Bird]

Ron, I think I'd pay heed to JacknCoke's advice myself. I think it's a safe bet that sooner or later you'll have moisture in that line that you want to get rid of.

 

[BobReeves]

Just had a thought, I understand how trying to blow water out of a line wouldn't completly clear it, but what about hooking a shop vac to one end and sucking it out. Anyone tried it?

 

[RonL]

Bird

The PVC will be just a conduit to carry the air hose to the shop and garage. The air hose will connect to permanently mounted piping with a drop for collecting and draining moisture. I want to isolate my air compressor in the shipping container that I have on sight, along with an electrically powered hydraulic pump to run the log splitter. The shipping container will evolve into my machinery building.

RonL