Pneumatic tools come in handy in a ton of different settings. For instance, you could use the same air tools in both automotive work and some woodworking projects, whereas electric woodworking tools may prove to be too weak to break rusty bolts. That said, your assortment of air tools is only as good as the air compressor, the very heart of any DIY mechanic’s arsenal.
In this guide, we’re going to talk all about air compressors, but we’ll focus mainly on the age-old problem of how big or small of a tank you need. Will 3 gallons suffice or should you go big or go home with a 30-gallon model? Read this guide to find out!
What is an Air Compressor?
Air compressors are machines that transform energy, either gasoline or electricity, into pressurized air used to power pneumatic tools. Air compressors force air into a specialized container that pressurizes it which is then moved into a storage tank for future use. The buildup of pressurized air is delivered to air tools via a valve where the tool connects. Imagine a balloon if you will; as soon as you open it up, air comes flying out.
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CFM and PSI
Not to take anything away from the size of the tank, but the most important factors to consider when shopping for an air compressor are the unit’s CFM and PSI ratings. The CFM (cubic feet per minute) rating indicates the maximum airflow volume that the unit can produce continuously, typically at 90 PSI. Similarly, PSI (pounds per square inch) is the maximum airflow pressure rating at which it comes shooting out of the valve.
The most appropriate air compressor for your garage, workshop, or whatever is a model that can supply as much airflow volume and pressure to power your air tools. For instance, air-hungry tools like orbital sanders require lots of airflows—between 6 and 9 CFM—at a constant 90 PSI, whereas finishing and brad nailers operate at lower volumes of between 1 and 2 CFM at between 60 and 120 PSI.
Why Does Tank Size Matter?
As for the size of the tank, it’s far from being a top priority, at least in the case of hobbyist workshops. To put it simply, the size of the tank determines how long you can operate your air tools before the air compressor’s motor needs to compress more air.
Larger tanks hold onto more air to supply air-demanding tools like impact wrenches, orbital sanders, and so on. They also require fewer pressurizing cycles to complete large-scale tasks simply due to their ability to store more air.
Another reason why the size of the air compressor is important is that has a direct correlation to how many cycles it needs to go through before you complete your project. An air compressor’s motor has a finite number of how many cycles it can go through before needing to be fixed up or breaking down entirely. If the tank doesn’t hold onto much air but you plug air-demanding tools into it, the motor will need to work constantly and becomes prone to heat exhaustion.
Say you were inflating a backyard hot tub that needs 120 gallons of air to fill. A 1-gallon tank would have to go through 120 cycles or run continuously to complete the task. A 30-gallon model would only require four cycles to finish the same job. However, to muddy the waters even further, larger tanks take more time to fill back up, meaning you might end up spending more time waiting on the 30-gallon unit to fill back up with pressurized air than with its 3-gallon counterpart.
3 to 30 Gallons: Which Tank Size Works Best?
There’s no way to tell which air compressor would work just by looking at the size of the tank. Sure, a larger tank generally means a more powerful motor and therefore quicker air compression, but that doesn’t paint the full picture.
As we mentioned in earlier sections, an air compressor’s CFM and PSI ratings are much more crucial considerations. If it can cover the airflow requirements of your most air-hungry tool, then there’s not much left to look for.
But let’s say you plan on using your air tool nonstop for between 5 and 10 minutes. In this case, a larger tank will facilitate your needs better than a smaller one. If you use tools intermittently—brad nailers, impact drivers, etc.—then a smaller tank will suffice.
Look at it this way: assuming six different air compressors with six different tank sizes meet your air tools’ exact CFM and PSI specifications, a larger tank will let you work for longer but also take longer to fill back up.