running an air line between two buildings-

stoneaxe · Dec 10, 2021

We have a woodworking shop and a small basic machining shop, about 12' apart- wood shop uses air all the time, machine shop does not have air at this time.
We are getting a new compressor and I want to run air to the machine shop- should this be done overhead or buried? If I bury it, how does the line get drained? -it will obviously be the low point.

LKeithR · Dec 10, 2021

stoneaxe said:
...If I bury it, how does the line get drained? -it will obviously be the low point...

Assuming you're delivering air TO the machine shop put a tee in the line just inside the shop. One line
feeds the shop, the other diverts outside (or wherever you want to exhaust the air). Put a gate valve on
both lines coming out of the tee. Normally the branch valve would be closed and the line valve would be
open. Periodically close the line valve and open the branch valve to blow out any water...

Cole2534 · Dec 10, 2021

If you go below grade you can build a drain leg. Need a few more pipe fittings but nothing wild. The trick is running a piece of tubing into the drain leg and out the top by modifying a swagelok fitting to allow the tube to pass fully through.

If you're interested I can sketch it up.

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BT Fabrication · Dec 10, 2021

with the freezing and frost heaving we have in the north. only thing id do is buy a second compressor.

john.k · Dec 10, 2021

I used to drain the underground airlines ocassionally......gallons of yelow oil,hundreds of gallons of oily water.....sound like a jet taking off...used to do it on the boss' day off....every so often ,a pipe would go ,and the air would tear up 40 feet of roadway.

michiganbuck · Dec 10, 2021

The amount of Ice you might expect in local lakes might be the minimum depth you need put undergrounds.

Overhead and both shops heated with haveing some grade (drop angle) in the line should be OK.

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Winterfalke · Dec 10, 2021

I'm thinking if you put a T at the end of the underground run pointed downwards, then loop back up to a valve, you can collect any condensate there and just put an auto-purge on the line to force the water up and out. For bonus points wire a button to it and aim the purge at your door to deal with unwanted solicitors...

Peter from Holland · Dec 10, 2021

Just install a air dryer between compresser and tank
No more moisture if dimensioned properly
Install it before the tank so it never sees a flow bigger as the capacity of the compressor
Not so if intalled after the tank

Peter

Homeshopblob · Dec 10, 2021

Peter from Holland said:
Just install a air dryer between compresser and tank
No more moisture if dimensioned properly
Install it before the tank so it never sees a flow bigger as the capacity of the compressor
Not so if intalled after the tank

Peter

I buried a piece of 3" PVC and pulled a rubber hose through that, alongside telephone and network wires and etc. Both ends of the PVC are above ground. The run is about 200 feet. I used a couple pieces of used hose for the first go, they needed replaced so I pulled a continuous piece of hose to replace it, that one has been there about 20 years without issue. My shop air is very dry however, I use a dryer also.

scsmith42 · Dec 10, 2021

I've done what you're asking about. In my instance the compressor is in the wood shop and around 150' away from the machine / equipment repair shop.

In my instance I buried 1" PEX approximately 18" deep, and it is sloped downward from the machine shop to the compressor. Inside the wood shop, the line from the compressor goes down 20" deep into the ground, where a T is located. One end of the T has a ball valve for draining the line.

I'll drain it every few months, but it's rare that there is any condensation. The exception is when I'm running the bead blasting machine almost continually in the equipment shop. Then it's a good idea if I drain the line a day or two later.

Typically the line has 150psi. The PEX that I used is rated for it and was an easy installation.

stoneaxe · Dec 10, 2021

scsmith42 said:
I've done what you're asking about. In my instance the compressor is in the wood shop and around 150' away from the machine / equipment repair shop.

In my instance I buried 1" PEX approximately 18" deep, and it is sloped downward from the machine shop to the compressor. Inside the wood shop, the line from the compressor goes down 20" deep into the ground, where a T is located. One end of the T has a ball valve for draining the line.

I'll drain it every few months, but it's rare that there is any condensation. The exception is when I'm running the bead blasting machine almost continually in the equipment shop. Then it's a good idea if I drain the line a day or two later.

Typically the line has 150psi. The PEX that I used is rated for it and was an easy installation.

There is enough vertical difference to do this- the compressor is on a wood floor about 2' above the dirt-and the machinine shop is at the floor level-so the line could go down to the dirt and then up to the shop, with a drain at the lowest point. Very rare to freeze here, I will run the line inside a conduit, that should do.

Thanks to all for suggestions, it is amazing how things get figured out when there are smart people to bounce ideas off of. It is my biggest complaint about a one man shop-it can be easy to miss the obvious, or fall into a rut by habit.

EPAIII · Dec 11, 2021

If you are determined to run a line, I would do it overhead, with heat tape and insulation. Or install a 100% dehumidifying system with a refrigerator dryer.

Someone above said the refrigerator dryer should be installed between the compressor and the tank but I would disagree. I ran systems with first the tank, then a copper coil that drains backwards, then the refrigerator dryer for years with not a single drop of water past the dryer. Most of it stayed in the tank and by the time it was past the copper coil, 99% of the moisture was removed. The dryer had an easy job after that. This is much, much better than before the tank.

moonlight machine · Dec 11, 2021

I ran a 2" diameter black pipe between 2 buildings about 15' high 25' long overhead about 25 years ago, no heat tape or any other bs. totally trouble free.

michiganbuck · Dec 11, 2021

re:....the line from the compressor goes down 20" deep into the ground,

That would/may not work at fish camp, where we can have over 30" of ice on the lake.

Yes, with snow cover it likely would be ok.

The Op is in the pacific northwest likely might get cold there.....? Seattle’s low, zero F is the record.

High with a little angle water runs to the low side. pipes would need be full-up to be a problem

Larry Dickman · Dec 11, 2021

how much air do you need for the shop? Could you just buy a large tank and fill it up every morning?

scsmith42 · Dec 11, 2021

michiganbuck said:
re:....the line from the compressor goes down 20" deep into the ground,

That would/may not work at fish camp, where we can have over 30" of ice on the lake.

Yes, with snow cover it likely would be ok.

The Op is in the pacific northwest likely might get cold there.....? Seattle’s low, zero F is the record.

High with a little angle water runs to the low side. pipes would need be full-up to be a problem

In my instance the drain valve is at the low end of the line. I simply drain it first thing in the morning when no air has been flowing through the line for the previous 12 hours. That way I know that any water has flowed back and accumulated near the valve. It's rare that anything more than a mist comes out though.

Seattle's frost line depth and mine here in NC are similar depth wise; around 5" - 10". Although we've seen low teens, it doesn't last more than a few days and the ground has never frozen pipes that are 18" deep.

idacal · Dec 11, 2021

all I know is don't use pvc I ran 1" pvc sched 80 about 200' 36" deep because I was also burying a water line. that thing had broken 4 times before i finally just quit fixing it, but it did run across and down a drive way. the water line, same pvc, same ditch, not problem. if i ever dig up the that route again it would be made so I could pull a line, poly, or pex, through. of course then it would never break

Bondo · Dec 11, 2021

If your talking 12 feet away, do it any way you want.

Bury it in a cheap PVC housing so you have a connection for anything. Even power if needed need to figure out a blow off.

Run it in the air, but put it on a slight slope so any water drains from 1 end. Put a blow off valve inside the building next to it with a 2' pipe so it can accumulate inside the pipe and you only have to blow it out once per day.

Run a flex line from door to door only when you need to. Pipe in both buildings but keep it on the flex line.

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HappyWyo · Dec 11, 2021

Run the air line over or under which ever is more convenient . The water accumulates in the tank just keep it drained. I had my lines running underground out to the gas pumps for years when I owned a gas station so customers could fill their tires. Never had a problem with freezing.

running an air line between two buildings-

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