Plumbing Your Air Compressor

Plumbing serves a couple of purposes when it comes to your air compressor. Not only does it allow the air to get from point A to point B in your shop or garage, but it can also help to cool the air which assists in reducing moisture. This is very important for powder coating and sandblasting, as well as any other pneumatic tool you may use including HVLP paint guns and standard air tools. The material you choose for your air lines and the way it is laid out can have a drastic effect on the amount of moisture coming out at the end of your air hose as well as the CFM provided. This article will help you decide how to set up the air lines in your shop or garage.

AIR LINE LAYOUT

There are a few basic guidelines when setting up your air compressor plumbing. Most of these guidelines are for efficiency and ease of use, however some are for safety. It is very important that your air compressor plumbing is safe. A burst pipe can be very dangerous or even deadly when it comes to compressed air. If you do not feel comfortable designing or installing your air compressor plumbing yourself, it is best to have a professional do it.
Disclaimer: This website and its owners are not responsible for any injuries or damages incurred from installing or using compressed air systems.

To help design your air compressor piping layout, also read How to Dry Compressed Air.

1. There should be a ball valve right at the outlet of the air compressor. This allows you to shut the air off for the entire system. If your air compressor plumbing ever gets damaged and bursts, you can shut off the ball valve and only the air in air lines will be able to escape instead of having to wait for your entire air compressor to empty. I shut off this ball valve whenever I will be out of the garage for more than an hour. It is very easy and cheap insurance. It also allows you to make repairs or changes on your air lines without needing to drain the whole air compressor tank. The internal diameter of this ball valve should match the rest of your air lines. If you use 1/2″ air lines, then use a 1/2″ ball valve. Most air compressor outlets are larger than you’ll need so you will also need an appropriately sized reducer for your ball valve. A male x female ball valve is ideal since the outlet of your compressor is female and the outlet of the air hose is male.

2. If you are using a hard material as your air line such as copper or iron, there must be a soft connection from your air compressor to the pipe. Air compressors create a lot of vibrations and if it is directly connected to your piping, all of the vibrations can lead to stresses in the pipes and possibly failure. Instead, after the ball valve, you should install a short piece or air hose to connect to your piping. This short piece of hose is called a whip or lead-in hose and it serves to insulate your piping from air compressor vibrations. These can also be braided stainless to which are more resistant to the heat right at the exit of your air compressor. In the picture below, you can see the air compressor outlet reducer, ball valve, and lead-in hose.

3. Your piping should be sized appropriately based on the CFM output of your air compressor and the length of pipe you will be running. A drop in pressure can be expected through any pipe, but having a pipe that is too small in diameter for the length of the run required can lead to too much pressure drop. Below you fill find a chart that will help you determine what diameter piping you should use. For most home powder coaters or shops, you’ll most likely be using 1/2″, 3/4″, or 1″ piping. When using larger diameter pipe like 3/4″ or 1″, the entire system does not need to be this size. It is acceptable to do the horizontal loop in the larger size and then neck down to 1/2″ for the drops. It is okay to size your pipe larger than needed without any negative effects, except cost. Some benefits of larger diameter piping is that it increases the overall capacity of your air compressor and it provides more surface area to the air, allowing the air to transfer more heat into the piping so it can cool down more quickly. I personally use a very minimal amount of pipe for my compressed air system. I have a two-car garage with a 60 gallon air compressor outputting about 12cfm @ 90psi. My piping run is about 25 feet and I use 1/2″ diameter copper pipe, however, I could have used 3/4″ diameter pipe as well. The only reason I didn’t was to keep costs down.

air compressor piping plumbing

air compressor piping plumbing

4. You should aim to use as few elbows, Tee’s, and connections as possible. Every single fitting you use contributes to pressure losses in your compressed air system and these should also be considered when choosing your piping size. If you know you are going to need a lot of bends due to the layout of your space, then it is best to go up at least one size in pipe. The table below shows the pressure drop through some common compressed air fittings based on CFM and pipe diameter. (ELL refers to elbows).
air compressor pipe size

5. The horizontal piping running around your space should not be completely level and instead should be sloped either away from or towards your air compressor. The choice of which way the pipes should slope has been debated about since the beginning of time so I will leave the option up to you. My train of thought is that it is best to slope away from the compressor with the flow of air and towards the moisture filter or drain. The important thing is that the pipe slopes, ideally about 1″ every 50 feet. The point of this is that you do not want water sitting stagnant anywhere in the pipes and this is a possibility if the pipes were all level.

6. Design your system so that there are no low-spots where water can collect. Air compressor piping should all run from the top down so that gravity can assist water downwards where it can be collected or drained from the system. Horizontal pipes should be run overhead with vertical drops running down to the air outlets. These vertical pipes are called drops and these are where you will connect your filters, air hoses, etc. The amount of drops you have is a personal preference. A shop with multiple workers and a lot of area should have a lot more drops than a home garage. Just keep in mind, that every drop you have should have its own particle/moisture filter to catch any moisture of debris before it runs into your air hoses so there is a higher cost associated with each drop you decide to add.

7. Drops should all run off the top of the horizontal pipe and then curve back down. The exception to this is the last drop unless you have a closed loop system. What this means, is that wherever you want a drop, you should have a Tee coming pointing upwards on the horizontal pipe, then two elbows to coming from the Tee to get it pointed downward again, and then you can have your drop. Because you make your air hose connections to the drops, it is best to minimize the amount of water that can enter the drops. With the drops coming off the top of the horizontal run, most of the water in the horizontal run will remain in the horizontal run instead of running down towards your drops. Notice in the picture below, how each drop runs off the top of the horizontal run except for the last one. The last one is where most of the water will collect and it can be drained from the system with a ball valve.

8. Each drop should have a length of pipe and a ball valve at the end to collect and drain water. Also, any connections you make to the drop should Tee off of the side of the drop and run upwards. This further allows gravity to assist in making sure that all of the moisture runs towards the bottom of the drop to be drained. You can see in the picture below how this would work.

9. Run at least 25 feet (more is better) of piping before your first drop. This initial piping before the drops allow the hot compressed air to cool down allowing the moisture to condense into a liquid allowing your moisture filters to catch it.

10. You should install unions in several locations throughout your compressed air piping if using copper, iron, or steel. Unions allow you to easily separate the pipes using a threaded nut. This allows you to easily disassemble your pipes for maintenance, additions, or removal.

Closed Loop or Linear Compressed Air Plumbing?

This refers to the horizontal run of pipes around your space. A closed loop system runs up from your compressor and Tee’s into pipes running in both directions where it meets on the other side of the room. There is no beginning or end, just a continuous loop. This can be seen in the picture below. This setup is ideal for larger garages or shops and especially if there is more than one person using compressed air at the same time.

A linear system is what can be found in most home garages. The pipe runs from the compressor and ends somewhere else in the garage. This is fine for one user with a short length of piping that goes that has drops on one or two walls. However, if you have drops on 3 walls in a room with 4 walls, there is no reason not to complete the loop. The benefit of this is that the drop that was originally furthest away from the air compressor with the highest pressure drop, now has a much shorter path to the air compressor and will have much less pressure drop.

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