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How to Run Compressed Air at Home


story by robert bowen

Okay, so you’ve read last issue’s shop article and you’ve bought that house with the eight-car garage that you always wanted. You didn’t think you would be able to get away with using that hand-me-down air compressor with all your shiny new air tools, did you? And surely you want to run compressed air lines to every corner of the garage, just like a “real” shop, right?

The question is, how to do it?

Well, you’re in luck, because we’ve done all the research you don’t have time to do. After reading this, you’ll be ready to choose a compressor and run air lines like a pro.

Air Compressors: the Heart and Soul of the System

The heart of a compressed air system is the compressor. Luckily, choosing an air compressor for a home shop is easier than it looks.

For one thing, we’re going to assume that your compressor is going to be used mostly for impact wrenches and hand tools, and see use mainly on the weekends. If you’re building a commercial shop with full-time bays, your needs are definitely a little more extreme, but the rest of us probably don’t need to run more than one or sometimes two tools at the same time.

One of the most important things to remember when shopping consumer-grade air compressors is that the horsepower rating is almost meaningless. Yeah, we know it’s printed on the side of the tank in big numbers, but the truth is that the horsepower rating on a compressor is not always the continuous horsepower rating of the electric motor, as one might assume. Instead, it’s usually a “peak horsepower” number that bears little relation to the continuous power output of the motor.

What is more important than horsepower is the compressor’s output of air in cfm, or cubic feet per minute. You want to choose a compressor that can supply the cfm requirements of all your most frequently used tools. Anything less and the compressor will have to work much harder to keep up with the tools’ air demands.

You can find cfm specifications printed on most air tools, but since we know you like to read in the bathroom and the tools are in the garage, we’ve listed the usual cfm requirements of some of the most popular air tools. Keep in mind that many tools are rated at “average cfm” which is assuming use only in bursts. If you plan on using tools that require constant airflow, such as most body tools, you can expect them to use as much as four times the rated cfm.

air tools cfm guide

If you get a compressor that can’t supply enough cfm for your favorite tools, be prepared for it to run constantly, and for the air tank to run out every few minutes. If you can only afford a marginal compressor, make sure it has a large tank and a high duty cycle rating.

Many cheaper compressors, unfortunately, are not rated for full airflow at all times—they have a duty cycle that can drop below 25 percent. These units are only able to run part of the time, and constant use will burn them up in no time at all. Check the numbers carefully, and err on the side of more use than you expect.

There are a couple more limiting factors that you should keep in mind for your compressor search, including the electrical power supply to your shop. For example, once you get beyond six cfm or so, you’ll start seeing that the compressors need a 20-amp circuit, rather than your average 15-amp circuit.

If you’re handy with wiring or have a 115-volt, 20-amp outlet available, no problem. If not, you’ll need to scale down your compressor size or beef up your electrical system. The really big compressors, say 10 cfm and up, usually require 220 volts. If you need anything larger than that, prepare to call an electrician to get three-phase power into your shop—which can be tough to do in some areas.

In addition to the different horsepower ratings. there are a couple of dominant compressor types—oil-bath and oilless. The oilless compressors shouldn’t be considered for frequent or heavy use. Yeah, they’re cheaper, but they will not last nearly as long as a good, multistage compressor with an oil sump. Get one with the largest tank you can find, since that will provide a larger buffer before the compressor has to start running again.

Other things you should look for in a quality compressor are belt drive, cast-iron cylinders and an automatic start and stop feature. Noise is an important factor, too, especially if you live in a residential neighborhood. A compressor with the lowest rpm at your needed output will be the quietest, all else being equal.

Once you’ve got your compressor in the shop and wired up, be sure to check the oil level every few months, as you would a car. Also, drain the tank of water weekly, or more often if you live in a humid area. If the tank fills up with water, it can rust from the inside out and cause leaks. Plus, all that water will end up in your air supply lines and tools.

How much is a suitable compressor going to cost? Budget at least $300 for a name-brand compressor that can support 6 cfm.

Plumbing: Bringing the Air to You

The best way to set up air in your home shop is to install a stationary compressor in a corner somewhere, and then run hard pipes to every part of the garage. This beats the heck out of tripping over long air hoses all day long.

Compressed air plumbing isn’t hard to do, but there are a few pitfalls for the DIYer. First, don’t use PVC pipe for air plumbing. This fact is so important that we’ll repeat it: Don’t use PVC pipe for air plumbing, even though it’s oh so tempting.

The plastic degrades over time, but more important, it is brittle and becomes even more brittle with exposure to sunlight and shop chemicals. A PVC pipe containing 100 psi of compressed air is a plastic grenade waiting to go off. Drop a hammer on it and you’ll be picking bits of PVC out of your legs for days. Take our word for it—we like our readers to be pain-free—and don’t use PVC pipe for air lines.

Some people prefer heavy galvanized cast-iron pipe for air supply lines, but we’re big fans of copper pipe. It’s easy to work with, almost as cheap as PVC, and ductile, so it will be less likely to rupture suddenly. Also, there is no galvanizing layer to flake off and get into your air tools.

Your best bet is probably to call a professional plumber, but if you insist on running compressed air lines yourself, start with the right pipe. Use schedule L or K copper pipe, which is thicker than the cheaper M type often used. Run 3/4 -inch lines for most home installations, since one-inch pipe probably won’t be needed.

Since condensed water management is always an issue, install the main lines with a downslope toward the air compressor, and install a water trap at the compressor connection. A long vertical pipe with a drain at the bottom and the air compressor inlet several feet above will work wonders for draining off water. At each drop to an air fitting, run the pipe past the outlet tee and install a ball valve to drain the water that will inevitably collect there.

Always think about water management. Mount your horizontal lines at a slight angle and let gravity take any condensed moisture to a water trap.

Run the lines around the ceiling, since that allows condensed water to run away from the main lines. Take each drop from the top, rather than the bottom, and turn it 180 degrees to run down the wall. You can use 1/2-inch ID pipe for the drops. Take the air from the lines with threaded/soldered tees. Solder the connections well, and pressure test each section of pipe if you can.

Always connect the compressor to the system with a short piece of flexible hose, as this will isolate compressor vibration from the hard air lines. Install a filter in the main air line as far as possible from the compressor but before the first outlet. This will prevent assorted gunk, including compressor oil, from getting into your tools. A small filter or pressure regulator can be installed at an outlet if you need precise control of the airflow (like with a spray gun, for example).

Breathe Easy

Accessory items like the Campbell Hausfeld IronForce in-line lubricator can help keep all your air tools healthy and happy.

Accessory items like the Campbell Hausfeld IronForce in-line lubricator can help keep all your air tools healthy and happy.

Many enthusiasts associate compressors and air tools with professional shops, but there’s no reason this same convenience and performance can’t be brought home. It just takes some planning, time and, of course, a couple of bucks.

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Comments

View comments on the GRM forums
Stefan
Stefan MegaDork
6/23/17 12:31 p.m.

What about the flexible hose kits? Any thoughts on those?

Tom_Spangler
Tom_Spangler UberDork
6/23/17 12:49 p.m.

I hear PVC is the way to go. (ducks)

codrus
codrus UltraDork
6/23/17 12:56 p.m.

I put a RapidAir kit in my garage last year and am pretty happy with it. Inexpensive and easy to install.

Zomby Woof
Zomby Woof PowerDork
6/23/17 1:14 p.m.
Some people prefer heavy galvanized cast-iron pipe for air supply lines,

You really should have a tradesman look through some of this stuff before you print it.

LifeIsStout
LifeIsStout Reader
6/23/17 1:59 p.m.

I just moved to a place with a garage so this is timely, that being said, any opinions from the Hive about the 21 gallon vberticle Harbor freight job?

Air delivery: 5.8 CFM @ 40 PSI, 4.7 CFM @ 90 PSI

Heavy duty 2.5 horsepower rated motor

Long-life oil lubricated compressor with precision machined cast-iron sleeve

I don't think I am going to be painting any time soon, this is more just for impact wrenches and other shop tools. At less than 200 bucks I was hoping it might fit the bill.

WonkoTheSane
WonkoTheSane Dork
6/23/17 2:30 p.m.
codrus wrote: I put a RapidAir kit in my garage last year and am pretty happy with it. Inexpensive and easy to install.

I've been running mine for two years.. I'm in love with the RapidAir stuff.

Bobzilla
Bobzilla MegaDork
6/23/17 2:53 p.m.

For mine, I run a 50' rubber 3/8 hose from the compressor, up the wall and to my hose reel. It's worked great for 6 years now.

floatingdoc
floatingdoc New Reader
6/23/17 3:33 p.m.

In reply to LifeIsStout:

I bought one a few months ago. Haven't got enough use from it to comment on it yet, only used to air up the fleet's tires. Seems like a good purchase so far.

It's my first "real" compressor, so I didn't realize how much more I would be spending on couplers, etc.

jimbbski
jimbbski Dork
6/23/17 3:39 p.m.

As for running air lines to places away from your compressor I have a rubber air line (50 ft.) running from my attached garage through my crawl space and to my work bench. I use the air for various things but mostly in my HF blast cabinet. Never an issue. I run galvanized pipe in my garage since at the time I did it I had a few lengths laying around so I only had to buy a few extra lengths. I also had most of the fittings all thanks to my father who was a pipe fitter by trade.

jere
jere HalfDork
6/24/17 10:21 a.m.

I also have a pretty janky ~$150 setup. I keep two compressors (both old Sears 1hp Campbell Haus one was $20 the other $80) in the house basement (not enough juice to power them in the garage). Then run 100ft orange hft 3/8 hose ($20) underground out to the garage with a tank in the loft, and hose reel(from what I can find about its a old schrader 1/2inch water/air hose reel couldn't say no for $20 hose and included). Added some quick disconnects and splices, "t"s in hose as needed. It's nice to have compressed air in the house too.

Been playing with making a free fridge into a dryer, but might just do the silica beads in pvc.

rslifkin
rslifkin Dork
6/24/17 10:35 a.m.

In reply to LifeIsStout:

On paper it sounds decent. Oil lubed compressors tend to be a bit quieter and longer lasting than the oil free ones (especially within the realm of cheap units). And it pushes enough air for good use of impacts, etc.

Toyman01
Toyman01 MegaDork
6/24/17 12:31 p.m.

I have a 75' hose reel mounted at the compressor. It will reach everywhere in the shop and half way down the drive. If I need to go farther, I have 2, 25' vinyl hoses.

SkinnyG
SkinnyG SuperDork
6/24/17 12:49 p.m.

I did my shop in copper because I got all the copper for free.

Copper was soldered together, then scrubbed with a green scrubbie, and clear-coated.

The main line slopes down to a final drain-only leg.

All air drops T off the top, keeping moisture in the main line.

Each drop has a drain valve at the bottom, to collect and drain moisture.

I put a ball valve on the bottom of the tank to make draining easier, but I will be running a timed blow-off drain thingie when I finish the compressor shed outside, getting the compressor out of the shop.

I really wanted a 7.5hp compressor, but you have to wire it for 3X the full-load-amperage for that initial current spike when it starts up. A 7.5hp compressor draws 31A, so I need to wire it for 93A. I only have 100A to the shop, so I ended up going down in size to a 5hp compressor. It still feeds my sand blasting cabinet and sanders fine, but it won't feed my air drill for long.

I also changed from Milton "M" couplers to "V" couplers - holy carp! Do these ever move air! Double the cross-sectional area - you almost need two hands to control the blow nozzle now!

einy
einy Reader
6/24/17 2:47 p.m.

PVC has worked for me for 12 years now. Compressor stays in the basement, line to garage disto system is pressurized when I need to use air out there. Regulator and filter is in basement by the plug in. Works like a champ, super easy to install, and low cost.

compressed247
compressed247 New Reader
7/25/17 12:10 p.m.

Hey guy! I think you need a normal compressor for your compressor

stuart in mn
stuart in mn UltimaDork
7/25/17 2:41 p.m.
einy wrote: PVC has worked for me for 12 years now. Compressor stays in the basement, line to garage disto system is pressurized when I need to use air out there. Regulator and filter is in basement by the plug in. Works like a champ, super easy to install, and low cost.

I knew someone would suggest this sooner or later...

People look at the pressure rating of PVC and figure it's going to be great for use as airline, but that is not the case. The pressure rating is for liquids, not gases.

When it's used with water or other incompressible fluids and if there's a break in the PVC pipe, the water just squirts out. On the other hand, if it's used with air and there's a break in the PVC the air expands out aggressively, which will cause the PVC to shatter into shards that can be dangerous. I've seen the aftermath of such an explosion, and the shards were sticking in the walls a long distance away. On the other hand, if you use a metal pipe for airline and there's a break, the metal just bends instead of shattering.

I haven't found any codes or regulations for home use (I think mainly because the various regulatory commissions don't take into account people running airline systems in their home garages) but it has been an OSHA violation for many years to use PVC for airlines. Also, the PVC pipe manufacturers all say specifically to not use their product for compressed air.

You're free to do what you want but be aware of the potential dangers, and do some research on your own as to its safety.

D2W
D2W Reader
7/25/17 6:04 p.m.

Don't use PVC as air piping its cheap and easy, but I have seen it come apart. It was in my works shop when we moved in. After one nice shrapnel inducing explosion it was all taken out.

PMRacing
PMRacing SuperDork
7/25/17 8:16 p.m.

Good timing and relevant to my recent post. Thanks!

stan_d
stan_d SuperDork
7/26/17 8:24 a.m.

What about Pex piping ?

spitfirebill
spitfirebill UltimaDork
7/26/17 8:46 a.m.

There are some types of PEX that are suitable. Even the basic PEX won't kill you if it blows.

D2W
D2W Reader
7/26/17 10:57 a.m.

My buddy runs an air compressor business and has a product he uses for piping industrial applications. It aluminum tubing with plastic fittings and hangers so you can run it in straight lines and have drops anywhere you want. Its also easy to modify if you want to add a drop at a later date. He was flirting with the idea of offering a basic kit to do a two car garage. What I like best about it is the nice straight runs vs the floppy hose or coiled aluminum that you can never get completely straight.

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