Q: I’m setting up a small woodworking shop and want to have places to plug in pneumatic tools at various places around the shop. What is the best piping to use for compressed air and do I need to worry about condensation?
A: Greg Burnet, a window and siding contractor based in Chicago and a presenter at JLC Live, responds: There are a number of options for piping compressed air. Some of the more frequently used materials are copper, black iron (or galvanized) pipe, stainless steel, PVC, and cross-linked polyethylene, more commonly known as PEX.
Systems piped with rigid metal offer resistance against accidental impact or puncture, but they are generally the most laborious and expensive to install. Of the metals, stainless steel and copper pipe and fittings are the priciest, and they’re most often used in larger commercial and industrial settings where permanence and durability are required. Special skills and equipment are required for handling these materials, so they’re often installed by plumbers or pipefitters.
A more economical material for a rigid-pipe air system is either galvanized or black iron pipe. But with all the fittings, couplings, lengths of pipe, and so on, installation can be complex and lengthy. Unless you have access to a pipe threader and dies, you will probably need to have some of the pipe cut and threaded by someone else. And because there are so many joints with this material, the potential for a leak is greater.
PVC seems to be popular for small shops. It’s inexpensive and fairly easy to install, and working with it doesn’t require any special tools. But if you decide to go this route, it’s critical to understand that not all PVC pipe and fittings are rated for use in this type of application. Most PVC pipe that’s sold for plumbing has a stamp on its side that reads “Not For Pressure.” Using PVC that is not pressure-rated for compressed air lines could lead to serious injury or damage if those lines were to burst.
At the very least, be sure to specify PVC pipe and fittings that are designed to be used for compressed-air systems. But be advised: PVC has other serious limitations. Compressed air typically contains some oil from the compressor, which coats the interior of the PVC pipe. Over time, this oil can lead to embrittlement with catastrophic results. Also, UV light can have a detrimental effect. Shops often don't get a lot of natural light, but if yours does, understand that it can degrade PVC.
Another option is heavy rubber air hose, which comes in 100-foot rolls. It’s flexible and connects with nipples and hose clamps available at most hardware stores.
My personal preference for small-shop compressed-air piping is PEX. It’s lightweight and flexible, and the fittings literally snap together. It’s the easiest of any of the options to reconfigure and the simplest to install. Because of its flexibility, you can often place PEX where it would be difficult to install rigid pipe, such as in finished walls and ceilings. PEX requires special fittings that may not be available at a home center or hardware store, so it’s best to map out your install ahead of time and order a few extra fittings. PEX pipe and fittings can be purchased online, and several companies, such as Rapid Air and Compressed Air Systems, offer packaged kits.
As far as condensation is concerned, it’s always wise to install condensation filters in a piped system, for several reasons. If you’re planning to use compressed air to spray finishes, it’s difficult to achieve a blemish-free finish if there is any water in the supplied air. Also, pneumatic tools work best and last longer when clean, dry air is used. Finally, moist air can contribute to rust and corrosion in both the compressor and any ferrous metal components in a piped system. Remember to drain the compressor and any in-line filters on a regular basis.