Compressed Air Basics - Piping

Your air compressor is the heart of your air system.  Most customers focus on the compressor and consider the piping as a secondary concern.  However, just like a heart can fail because of clogged arteries, a compressor can fail because of improper piping.

You have many different options on the type of piping, and how you pipe your compressed air system,.  Before you choose an option, you need to know what you want from your piping.

So what do you want from your piping?

1.  You want your pipe to be leak free.

Leaks are very bad for your bottom line.  We have mentioned that several times on this blog, so there's no need to go over that again.

2.  You want your pipe system to have a minimal pressure drop.

As we discussed earlier, every 2% increase of psi over 100 psi increases your energy costs by 1%.  Every pipe system will have some pressure drop.  There's no way around it.  Pressure drop is caused by the friction between your pipe and the air that runs through it.  Frictionless pipe has not been invented yet, so pressure drop will always be present.  The key is to minimize it as much as possible.

To minimize pressure drop:

a.  Make sure you have the proper pipe size for the CFM, pressure, and length of your pipe system.  The longer you go, the bigger the pipe will need to be.  We have charts and excel spreadsheets that calculate pressure drop in piping.  You can also look on-line for numerous pressure drop calculators.  Make sure you include the equivalent length of fittings in your calculations, which brings me to "b."

b.  Minimize the use of elbows and bends.  An elbow counts as several feet (or possibly several hundred feet) of pipe when looking at pressure drop calculations.  Sometimes you can't avoid elbows because there are things in the way, but do your best to minimize them.  For a more in depth discussion on it, look here.

c.  Make a loop.  A loop will make it so the pressure is spread evenly throughout the system.  You won't have a lack of pressure at the end of the line.  A loop also makes it easier to expand later.  If you can make a loop, do it.

I recommend CAGI's pressure drop calculator.  It's very comprehensive, and includes the equivalent length of fittings in the calculations. 

3.  You want your pipe system to last.

Avoid PVC; it's illegal and not meant for compressed air.  It will crack and break eventually.  You can read more about it here. 


Avoid black iron.  Black iron used to be the go-to pipe for compressed air installations (that and copper).  However, black iron will corrode inside and out.  The corrosion on the inside is really bad for your compressed air quality and your pressure drop.


Galvanized steel, copper, stainless steel, and aluminum are all good choices.  Which one you choose will depend on many different variables, and we'll go into that on a later post.

Get a professional installer.  I know a lot of you are wrench turning experts, but there are important codes, regulations, and best practices that you probably won't know.   If you're a car mechanic you get really good at it by fixing cars day after day after day.  If you work on forklifts, you get good at it by fixing them constantly.  I'm sure a skilled car mechanic can do a decent job a fixing a forklift.  However, he won't do the job as good as a forklift expert.  It will take him longer and he won't know all the little tricks that the forklift mechanic learned through experience.  A pipe system should last decades if installed correctly.  You want to install it and never worry about it again, and that's why you need a professional compressed air pipe installer. 

Other considerations

1.  Plan for the future.

Make sure you can easily expand or make another drop.  It's easy to do this when it's first installed, but it's a hassle and costly to go back and modify, unless you have a modular piping system.  You might want to oversize your pipe if you think that expansion is likely.  The bigger pipe will never hurt, and again it's a hassle to go back and change your installation.

2.  Drip legs.


If you don't have a refrigerated, membrane, or desiccant dryer, then you need to put drip legs in your pipe.  Compressors squeeze a lot of water out of the air.  A filter will only get out some of it.  If you don't have a dryer, more water will condense in your pipe.  This water has to go somewhere - either it will get into your equipment or it will flow back into your compressor.  A drip leg will catch this water.  Remember to drain it or have an automatic drain on it.  Drip legs are very easy to install.  Even you have a dryer, you should put some in just in case it fails.

3.  Ball valves and unions.

You need a ball valve before and/or after every major component.  Eventually something is going to break and you're going to have to fix it.  A ball valve lets you isolate it from the system.  You should also have unions before or after major components and between pipes.  If you have to change something out, this can save you hours of labor.  Unions can also make the installation go much faster.

Your Pipe is Important

Your compressed air pipe can greatly affect the performance of your compressor.  I would argue that good piping is just as important as a good compressor.  I have certainly seen bad piping ruin a compressor -in fact it's very common.  Don't overlook how important it is.  In the next post, we'll talk about what type of pipe to use.