underground compressed air line?

James Wieler · Dec 28, 2015

What would you use to deliver compressed air to an adjacent building? I don't want to buy another air compressor, I want to put my air compressor in a separate shed in the back yard and run a line to my shop so I don't have to listen to it running all day.
The line must run underground. At first I was think of using steel pipe but I guess I could just bury a silicone air hose too. Anybody got a better suggestion?
thanks
James

matt_i · Dec 28, 2015

Its going to be a magnet for water, always. Lowest point plus nearly always colder than ambient air. If you can rig up a low-er point drain then it is probably viable.

nh_yota · Dec 28, 2015

One important thing you need to take into consideration is the condensate in the air line and the possibility of it freezing during the winter. If you have a low spot in the line and it's not buried below the frost line, well you know where I'm going with this.

NUTTSGT · Dec 28, 2015

I might consider some PVC conduit and run the air hose inside it. If you use a larger diameter conduit and some sweeps rather than 90° elbows I'd think the air hose might be fairly easy to push through it.

404 · Dec 28, 2015

NUTTSGT said:
I might consider some PVC conduit and run the air hose inside it. If you use a larger diameter conduit and some sweeps rather than 90° elbows I'd think the air hose might be fairly easy to push through it.

That is exactly what I did. I ran 2 hoses parallel for more flow, also if one broke I could just use the other.

jonjon1 · Dec 28, 2015

I used this, its worked perfect so far...
http://www.amazon.com/dp/B005FKYRTU/?tag=atomicindus08-20

Direct buried about 15"s down, well the trencher was set at 15" then we put a bed of sand, laid in the electrical and air hose, then more sand to cover it, and then back filled it with clean fill...

Dont over think it, if digging trench is a big deal for you, I would maybe bury some conduit for future use with a rope in it, but the important things are sand and don't back fill with the bony garbage that came out... I drive over the spot that my trench crosses with heavy equipment so I went 15"s, you can go 5" if you are never going to drive over it...

ishiboo · Dec 28, 2015

PEX.

If you want a guarantee, use PEX-AL-PEX.

CNGsaves · Dec 28, 2015

^ ^ ^ Good advice above.

#1 habit EVERY DAY is blow out any moisture in your system. Install water traps before and after that low underground leg of your airline system.

Dustball · Dec 28, 2015

PEX would be my suggestion as well.

James Wieler · Dec 28, 2015

jonjon1 said:
I used this, its worked perfect so far...
http://www.amazon.com/dp/B005FKYRTU/?tag=atomicindus08-20

Direct buried about 15"s down, well the trencher was set at 15" then we put a bed of sand, laid in the electrical and air hose, then more sand to cover it, and then back filled it with clean fill...

Dont over think it, if digging trench is a big deal for you, I would maybe bury some conduit for future use with a rope in it, but the important things are sand and don't back fill with the bony garbage that came out... I drive over the spot that my trench crosses with heavy equipment so I went 15"s, you can go 5" if you are never going to drive over it...

Awesome find Jonjon, that looks perfect. I add a drier upstream and that should minimize the moisture in the line.
cheers
James

rsanter · Dec 28, 2015

If it was me I would bury PVC and then feed a hose through it like has been said.
Then I would install a small tank in the building that it goes into so you have a place for the condensate to collect. Pull off the top of the tank for the air you will use and have a water separator there

And ball valves at both ends

Bob

CNGsaves · Dec 28, 2015

^ ^ ^ Low cost way to dump water in that segment could be a ball valve . .
. . . . . WITH RELIEF . . . the small thumbscrew where you'd dump out pressure from the underground segment that might have water.

May Pop · Dec 28, 2015

I buried 3/4 galvanized. I bent the pipe with a bender. About 12" down with a continuing downward slope to a point where it can be drained. It has been in the ground at least 15 years. never a moisture problem.

Ron

toomany · Dec 28, 2015

I used PEX to get from my pole barn to my house garage 250' away. No issues so far.

kingchevy · Dec 29, 2015

I used 1" electrical conduit and sweeps to go about 80' from compressor to shop. For now I just pushed an air hose through it but plan to replace it with air brake tubing. No issues with water that I notice.

homebuilt burner · Dec 29, 2015

3/4" dot nylon air line used for air brakes on trucks. Cheap, Quick, and made to stand up to dirt/cold/salt/water.

MatBirch · Dec 29, 2015

I run a large outdoor "shop" operation with 4-8 guys running high volume tools all day, plus a 20x30 shop building off a 1" Goodyear rubber hose in a 2" PVC conduit. We run a large air drier off of a 25Hp screw compressor in our main shop. The run is about 150'. we see a small amount of drop when several guys are going full tilt on air drills, but otherwise it's been a great setup for 3 years now. It froze up on us once early this winter. That's how we discovered that the air drier had taken a dump!

jonjon1 · Dec 29, 2015

James Wieler said:
Awesome find Jonjon, that looks perfect. I add a drier upstream and that should minimize the moisture in the line.
cheers
James

No problem, and its made for it.. Also cheaper than pex equivalent, plus you get a bunch of fittings and nice aluminum blocks with valves to use (and the tools).. I also use the 1/2 stuff inside, it works great...

good luck, I have used it a few times so if you have any questions let me know..

bdbecker · Dec 29, 2015

Just be sure to do your math on how long/big of hose or line you plan on running. The link below starts off with water, but halfway through goes to air calculations.

http://www.reelcraft.com/pdfs/tech_bulletins/TB0001.pdf

Its pretty surprising how quickly pressure drops over distance, especially in smaller diameter hoses.

larry4406 · Jul 8, 2018

Waking this old thread up.

When trenching to my detached barn for running power, I was thinking of installing RapidAir line in the trench. One of the posters (jonjon1) in this thread showed positive experience with this product in a buried installation but he has not posted since 12-13-16.

This is a 3/4" kit (0.8" inside diameter) including 300' of tubing and some basic fittings for $375.
https://www.northerntool.com/shop/tools/product_200581018_200581018

The manufacturer specifications list this for buried applications but specify to protect from UV rays where exposed. I can easily achieve this.
https://www.rapidairproducts.com/page/maxline

My compressor is a Puma TUE-7580VM, 7.5HP Baldor, 24.6 cfm @ 100psi and 22.8 cfm @ 175 psi.

Their on-line calculator shows that for 175 psi input, an inside diameter of 0.8", and a run of 300', the line would flow 51.88 cfm. At 100 psi input with same parameters it would flow 39.98 cfm.
https://www.rapidairproducts.com/page/flow-rate-calculator

This theoretical air flow is more than my compressor output so I am thinking the size is adequate.

The airline would be buried below the frost line as the same trench will also contain a water line.

My actual total length would probably be closer to 250' and would be a continuous run with one end in the garage attached to the house (where compressor currently resides) and the other in the detached barn. I understand water traps would be needed. The barn is at a lower elevation than the attached garage.

At some point in time, the barn will serve as a paint booth for my project car.

Thoughts?

FTG-05 · Jul 8, 2018

larry4406 said:
Waking this old thread up.

[snip]

Thoughts?

Big tank at the non-compressor end.

Good luck!

larry4406 · Jul 8, 2018

FTG-05 said:
Big tank at the non-compressor end.

Good luck!

Not a bad idea. My brother has a large horizontal new tank (I’m guessing 30+ gallons) I could put on the non-compressor end. It’s just collecting dust.

rburke65 · Jul 8, 2018

I ran 2” pvc and pulled pex tubing from pole barn....and compressor, to new shop.

MattT · Jul 9, 2018

larry4406 said:
Not a bad idea. My brother has a large horizontal new tank (I’m guessing 30+ gallons) I could put on the non-compressor end. It’s just collecting dust.

If you do use the tank you could drop down to 1/2" line unless you're doing something like blasting that'll need the full compressor output for a long duration. The tank will be enough to cover short term high cfm demands like impacts.

Just check the tanks pressure rating. You might need to regulate down & install a pressure relief since your compressor is 175psi.

larry4406 · Jul 9, 2018

MattT said:
If you do use the tank you could drop down to 1/2" line unless you're doing something like blasting that'll need the full compressor output for a long duration. The tank will be enough to cover short term high cfm demands like impacts.

Just check the tanks pressure rating. You might need to regulate down & install a pressure relief since your compressor is 175psi.

Blasting will be part of the program.

Anyone with underground RapidAir experience?

sberry · Jul 9, 2018

Blasting doesn't take a large line.

NitroGarage · Jul 9, 2018

PEX. Wouldn't be bad for a compressor shed to keep all the noise outside, too.

GrayFlattop · Jul 9, 2018

I have used "DOT Air Brake Tubing" with good success. It's made of Reinforced Nylon, flows air beautifully, is rated for pressures higher that you will ever expose it to and won't rot.

The size you use will depend on your requirements, but 1/2" or 3/4" would fill most needs. http://www.parker.com/literature/Parflex/4660-1120.pdf

If you want to "future-proof", run the tubing inside a larger PVC conduit so you can pull a larger size through later if you need to. I have 1/2" running between the house and garage - and it has been fine for thins like air nailers, etc.

HoosierBuddy · Jul 9, 2018

The only thing I see missing from your design is allowable pressure drop between your compressor and your outbuilding.

Do the tables you look at say what pressure drop they are basing their flow on?

If that is based on "all of it"...like they are saying if you have 175 on one end and the other end open to atmosphere than that isn't a useful flow number. Does that make sense? There has to be a pressure differential or there wouldn't be flow...

Phil

PS>>>NEVERMIND. I clicked on your link. They are basing their flows on a 5 psi pressure drop, which is very conservative. So on your 100 PSI example, that's the flow with 100 inlet and 95 at your garage 250-feet away.

sberry · Jul 9, 2018

That is not the best of charts. Pex makes a good one, have the link somewhere but 2x as simple and 2x as accurate. About the only good thing they got on that one is the hose drop. The tool demands are terrible and not well explained and if you use those figures would starve the tool while some of the rest is over done or conservative as they say. Note that the demand on some of it doesn't start till 40cfm and then only at 100# which is at secondary pressures of a 2 stage, the user end and is where Reelcraft is focused,,,, or for a single stage system.
A 1/2 pipe,,, which is a bit bigger than a tubing but a primary on a 2 stage only drops a couple # using a 1/2 air gun at 100 ft. There is a lot of focus on blasting but,,,,, usually only to about the output of a compressor, even 20 is a lot for this crowd. A 3/8 hose will quickly drain 5 hp unit on a blaster, 1/2 will run 75 cfm easily on blast. 200 down a 3/4

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