How to Run Compressed Air at Home

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.

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.

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.