Compressor Air Line Size

[lzicc]

I am getting ready to plumb my compressor air lines. The longest part of the run would be about 60'. I was going to use 1/2" black pipe the whole way. Would 1/2" be large enough? I have a threader for 1/2" pipe and really didn't want to buy the die for larger pipe since the dies are not cheap.

 

[gatchel]

Depending on your needs and demand you should be fine. Use this to get an idea:
http://www.engineersedge.com/pipe_flow_capacity.htm

 

[Kevin54]

I wouldn't use less than 3/4" for piping it. Size it up as to what you need and get a plumbing shop to thread it for you. Shouldn't cost too much. I'd say they would be better than some of the yayhoos at Lowes or HD in threading it.

 

[sberry]

Anything a notch below a class 8 truck shop , multiple men, larger tools etc a 1/2 is going to work fine. You got the threader, 1/2 is as easy cheap and common, 3 times or more than the flow of 50 ft of 3/8 hose.

 

[Shadowdog500]

This is a more intuitive table to look at.
http://www.engineeringtoolbox.com/compressed-air-pressure-loss-d_1014.html

From your other thread I see you have a 5hp compressor so you probably have 15 to 20 cfm continuous delivery. At 100psi flowing 20cfm through 1/2" pipe would give you a 1.6 psi pressure drop per hundred feet. 3/4" would give you .4 psi pressure drop using the same conditions. If you have a threader and 1/2" pipe on hand you could run a loop around your shop so it feeds air in both directions from the compressor which will reduce the pressure drop.

Chris

 

[sberry]

He is worrying for nothing looking at the tables, I mean its a great thing to know but even on full load gonna lose less than 2 # only 1 # better than a 3/4 and the drop across any hose or fitting on this line would/could be multiples of that depending on flow rate, this all assumes it is actually above 1/2 capacity, the lower the use the less important pipe size is. You wouldn't gain with use 24/7 let alone in a home hobby shop or even small garage.

 

[Roothawg]

I ran 1/2" and I never run out of air.

 

[Provincial]

I can run a 1" impact wrench with a 1/2" pipe feed over 100 feet long. Unless you are going to run a big sandblaster at the far end of the shop, 1/2" should work fine. I used bigger (1") pipe for my new system, but I have need for more air flow than most.

Since you have the threader, go with the 1/2". Don't go any smaller.

 

[rwhite692]

I did my whole 24x36 shop in 3/4" black pipe, but it really was not necessary.

1/2" would have been just fine. I almost never run more than one air tool simultaneously.

Agree with exactly what Sberry said.

I think I wound up doing mine in all 3/4" mostly because I already had some of the pipe and a whole mess of fittings.

 

[lzicc]

From the sounds of it, 1/2" should suit me fine then. It will be just allot easier overall for me to run that. Plus, it beats the heck out of running PVC. I know, don't go there.

 

[lzicc]

One other question, I am looking on Lowe's website and the 10' sections of 1/2" black pipe is saying 150 psi. Is that right? I would have thought it would have been higher than that. My air compressor shuts off at 175 psi. I was going to run it full psi to each outlet then use a pressure regulator from there.

 

[Torque1st]

Check out this chart:
http://www.kahlenberg.com/pdf/dimensionsofstandard.pdf

 

[lzicc]

That sounds more appropriate.

 

[Roothawg]

FYI, I used zinc coated (galvanized) water lines. They don't have the oil coating on them, about the same price.

 

[Falcon67]

1/2" is plenty. Unless you have a mondo compressor, you'll run out of compressor before you run into a pipe restriction.

 

[Shadowdog500]

Check out this chart:
http://www.kahlenberg.com/pdf/dimensionsofstandard.pdf

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[Torque1st]

The link is to a PDF document. It has worked every time for me and apparently for the OP also.

 

[Charles (in GA)]

Link worked fine for me. Also, in doing calculations, you need to add 10 ft for each fitting when you are calculating pressure drops. If you have 50 ft of pipe, and 5 fittings (elbows, t's etc) then you have the equivalent of 100 ft of pipe when using the charts to calculate pressure drop/flow loss.

Charles

 

[lzicc]

I guess I could buy 3/4" sections and run them along the ceiling to the air compressor for the main air line and then T off with 1/2" down the wall for an outlet. It wouldn't be that big of a deal since they would already be threaded.

 

[sberry]

It wouldn't be that big of deal especially considering the threading but we do get back to the original premise of this thread, the air demands of the user. I like the diagram Torque posted, I also like some added such as experience and judgement, some it over extended time, none of it will make any difference or be noticeable in any way, Even using a greedy professional air tool it will be about like using 15A on a 20A circuit and even with a load drop type of tool it would be so split second, totally irrelevant.

 

[sberry]

Even hi draw like sandblast, whats 1 psi difference across the hi side, the user would never notice and get the work done just the same as thru a larger pipe.
My own case, I can probably deliver twice or 3 times the air really dont have demand, there is no work that doesnt get done because I dont have a bigger pipe.
Water is where my demands are different, I use 1 inch for mains and 3/4 for hydrant drops with full ported ball valves. Some with 3/4 gargen hose running greedy little sprinklers and cases where I want to dump/fill from them. Want to open a hose wide open, usually with air you are running thru tool or fitting.
This is a consistant area that causes way too many people way too much anguish, the OP had the right idea, plumb a 1/2 steel line to the point of use, put regulator on, connect hydrants, lines, hoses, hose reel, etc. I like a ball valve soon after the comp so I can work on the air, you can change it at any time.

 

[sberry]

Here is one that has 5 taps and you can get hi pressure before the reg if needed. One reg feeds about 8 regulated whips. The second is simpler, the main reason it feeds my outdoor hose reel.

 

[MoonRise]

As mentioned, 1/2 inch 'iron' pipe is probably enough for a home shop.

3/4 inch 'iron' pipe is almost certainly plenty for almost any home shop.

Slight 'overkill' in air piping is almost never a bad thing, and gets you a wee bit more air 'storage' in the piping compared to the smaller pipe for usually just a few $ more in pipe costs. Also gives your pipe walls a bit more surface area (30% greater wall surface area and 75% greater flow area than 1/2 inch pipe ) to help in cooling down the air stream after it is compressed (which helps the water vapor in the air stream to condense out and go back into liquid form. And no, a typical air filter does not filter out water vapor from the air stream, just water droplets).

That's for a 'typical' home shop and home shop type tools.

If you're running a scroll compressor and a pavement jackhammer, then you'd have to upsize the piping a wee bit more to handle things though.

Plain 'black' pipe is usually recommended for air lines, as the galvanized pipe is typically not needed and may drop flakes of zinc into the pipe and air stream.

IMNSHO and YMMV.

 

[Mmfh]

Is there any advantage to using the 1/2" black pipe over the 1/2" copper? Flow should be about the same, cooling the air would probably be better with the iron pipe.

I like working with the copper, and find it much easier if you don't have a threader. What is a typical psi rating of a sweated copper joint? Anybody know?

Mm

 

[sberry]

I went back and looked at that chart again, that is really good and practical, I see they even give HP estimates and the written word is well thought out.

 

[ixlr8]

I like working with the copper, and find it much easier if you don't have a threader. What is a typical psi rating of a sweated copper joint? Anybody know?

Mm

Depends on what you 'sweat' the pipe with. 50/50 and 95/5 have very different ratings, to be sure it will hold you could braze it. I found a copper pipe hand book online once, can't find it now and my printed copy is at home. IF my foggy memory serves, the 95/5 will hold at least twice the pressure as the 50/50, enough so you are more worried about the pipe bursting before the solder joint fails.

Found the copper pipe handbook-
Copper.org handbook
For 1/8"-1" copper pipe, at 100dF/at 150dF/at 200dF;
50/50 solder- max working pressure of the joint is 200psi/150psi/100psi,
for 95/5 solder- max working pressure of the joint is 1090psi/625psi/505psi.

Note from the handbook; "For continuous operation at temperatures exceeding 250°F, or where the highest joint strength is required, brazing filler metals should be used "

HTH

 

[Mmfh]

Thanks Jim,
Sounds like if a person used the 95/5 for an air system it would be more than strong enough.

Thanks

 

[Torque1st]

I guess I could buy 3/4" sections and run them along the ceiling to the air compressor for the main air line and then T off with 1/2" down the wall for an outlet. It wouldn't be that big of a deal since they would already be threaded.

The only time you need to thread anything is when you are working to some tight +/- 1/2" tolerance specified by an architect. For home shops +/- 3" is probably OK and can be easily attained by using standard stock parts from Lowes/HD or the supply house. There have been many complaints registered here about the Asian fittings and poor threads. I think those Asian fitting threads have improved immensely but there are still QC issues. Using Rectorseal #5 pipe dope seems to take care of most leak issues.

You can find diagrams on how to lay out the pipe system and make drops here:
http://www.tptools.com/StaticText/airline-piping-diagram.pdf

Remember to keep your lines out of the dead air space near the ceiling etc. Some people have had very good luck running the lines low on the wall and using risers instead of drops. It kind of depends on your layout and whether you have door openings to work around. Many people use galvanized pipe (including me) to reduce rust issues. I live in a humid area.

1/2" is OK for most home shops, as is 3/4" as noted before.

 

[rwhite692]

The only time you need to thread anything is when you are working to some tight +/- 1/2" tolerance specified by an architect. For home shops +/- 3" is probably OK and can be easily attained by using standard stock parts from Lowes/HD or the supply house.

I can attest to that, I did not have access to a threader when I did my shop (all in 3/4) and I just used standard lengths and fittings to get everything lined up as it needed to go....all of my plumbing is inside of the finished walls and ceiling.

 

[Falcon67]

The only time you need to thread anything is when you are working to some tight +/- 1/2" tolerance specified by an architect. For home shops +/- 3" is probably OK and can be easily attained by using standard stock parts from Lowes/HD or the supply house. There have been many complaints registered here about the Asian fittings and poor threads. I think those Asian fitting threads have improved immensely but there are still QC issues. Using Rectorseal #5 pipe dope seems to take care of most leak issues.

This. I plumbed the old shop with all standard fittings and off the shelf pipe doodads. I took it all with me when we moved to save $$. A pro race plumber friend said to wrap the china threads with teflon and add 2-3 wraps past what you think is "good", then add seal on top. "Test and hope for the best." On little cheap fittings like 2-4" stubs with a T that leaks a little, I've been known to just JB Weld and the hell with it. Not enough money in the fittings to waste my time later. For drops I found that a T, 4' joint, gate valve, 1' stub, T, 2' stub and a gate valve make a nice drop for an 8' ceiling. Build in sections and add unions - one leak in a 20' run with a turn and a couple of drops will make you nuts. Helps line things up too.

 

[MustangRick]

A plumbing supply store carry longer lengths such as 20', that may come in handy to eliminate some leak points on a long run.