In-Line Compressor and Tank Devices

These are extra things you can buy to put put in-line with the tubing of your tank and expand it's functions. Some of them protect it, like a water / dust trap, others make your life easier such as a quick release valve and finally there are a whole bunch of splitters, regulators and valves to expand on how much control you have and how many people can use it.


Sizing and Terminology

For reference, and when you're looking for anything to connect to the line, compressors use attachments called NPT or National Pipe Thread. (North American) In other parts of the world, this rating may be different, for example, the BSP or British Standard Pipe thread.

The size that air compressors use is quarter inch.

So, what you're looking for is 1/4" NPT.

In-Line Devices

• Water / Dust Trap

The first “must” (or “eventually” if you can’t afford it right away) is a filter that’s designed to catch dust and/or water. Pressure squeezes water out of air and if it gets into your line, can cause bursts and spotting as you paint. Dust will cause other problems like dirt build-ups and clogging over time.

Cleaning the filter is a simple matter of unscrewing the bottom to let out water and dust, and replacing the internal filter as required.

It's recommended to place a trap as near your tool as possible - however as I explained with airbrush traps, I don't want the extra weight while I'm painting, so I place it right after the compressor instead.

• Quick Release Valve

The other more common attachment is a quick release valve. If you plan on using other attachments with your compressor, this is really handy so you’re not constantly undoing and tightening fixtures. While not as big of an issue for smaller hobby compressors, higher end ones need stronger and tighter connections made using teflon (plumbers) tape. This makes constantly undoing / redoing compressor tubing connections a pain.

It’s just two parts designed to click together. Yes, they're called "Female" and "Male" adapters. Can you guess which is which?

• Manifold (aka, a splitter)

Multiple people can work from a single tank with one of these. It allows you to split your feed to more than one tool and/or place. It’s a simple matter to just split the feed so you can work in different places but gets more expensive if you want to be able to use two (or more) feeds at the same time.

Keep in mind that if your tank is only providing 35psi, two airbrushes (or other tools) at once means your pressure gets split between two devices and won’t be enough to run either one of them; while turning the air up to 70psi would damage both of them. The solution is to use a regulator. (see below)

Splitters are available to split from one to two or three or four or more... or you can connect multiple splitters together.

• Valves

This leads us to valves, which allow you to open or close a line at some point. Essentially, an ON or OFF switch. The third valve pictured below creates a dead end (so you'd need to put it on a splitter) and releases air when you pull on the ring. (For example, on a tank to empty it when you're done.)

For example, if you have a compressor / tank in your garage then you might want to use it in both the garage and your hobby room. (one at a time only) Therefore, you put a splitter on the output, have a small tube in the garage and a long tube run to your hobby room with a closed valve on the end of each tube. To work at one place, open it’s valve up.

If you use any kind of valve to adjust pressure (by closing it half-way for example) the pressure on the line doesn't change - it would be like using a smaller tube.

A Regulator (explained below) is different, in that instead of being ON or OFF, it can adjust the actual pressure on the line.

• Automatic Release Valve

Not something hobbyists usually need to worry about, but I'll briefly cover them. An automatic release valve is something placed in-line with the tube to slowly release line pressure. Normally this isn't used for airbrushing, but for a line where you'd want to maintain a constant pressure. You set a valve to a certain pressure and if the pressure on the line exceeds it, the extra is vented out into the air.

A Regulator (explained below) is the usual thing we would use to control pressure passing through a line for our uses.

• In the first photo, it shows that if the valve isn't set, it lets all the air through.
• In the middle photo, the valve is set to 15 psi, meaning you want to ensure that no matter what the pressure on the line is, only 15 psi gets through and the rest is released into the air. 
• In the last photo, the valve is set to 25 psi. The line pressure is 30 psi, so the extra 5 psi is released to the air.

These valves don’t solve everything as some might only be able to release so much pressure at once.

In the above example, say the auto release valve is set to 25 psi, but the line is at 50 psi instead of 30. That’s 25 psi too much and the valve will start venting to the air – HOWEVER, your automatic release valve might only be able to release a max of 5 psi. This means you’ll still have an extra 20 psi on the line.

• Gauges

A gauge is only a meter that shows the pressure on the line and usually doesn’t include a valve to adjust the pressure.

To continue with the above example, you’re in the hobby room and have no idea what the pressure on the line is – unbeknownst to you, it’s at 70psi and could damage your airbrush. If you place a splitter on the line in your hobby room, you can attach a gauge to one of the outputs. This way, you can at least see what the pressure is on the line and know that you’ll have to run to the garage and turn down the pressure.

• Regulator (Gauge w/ Pressure Controlled Valve)

A regulator is basically a fancy valve AND a gauge in one that give you much more reliable control over the pressure on the line. Not only can you see what the pressure is at as you adjust it, but the output pressure will remain the same even if your input pressure increases. (Unlike a normal valve) Compressors and tanks come with these – it’s what lets you set the line pressure in the first place.

Make sure your regulators can handle that much pressure. Shouldn’t be a problem for most, but hobby grade ones might have lower pressure maximums. Also, regulators can be expensive...

If you start splitting or extending the line, you may want control over the pressure where you’re working or to allow multiple people to work at once. (As a bonus, each person can work with different pressures.) The main pressure will have to be set high enough that it can supply both regulators at the same time.

Once again, you’ve got a compressor / tank in the garage and a splitter to supply air to both the garage and your hobby room. Instead of a valve on both ends, you could use a regulator. That means that in the garage, a regulator could be set to 70psi for tools and 35psi for your airbrush in your hobby room. The main compressor would need to be set to at least 105psi (preferably higher) to supply enough pressure to the line that both tools can be used at once. You won’t damage your tools/airbrush because the regulators will only allow so much pressure through.

Another example would be this: Maybe you don’t want to split the line at all, but you do want to keep the compressor in your garage to avoid the noise. This just means running a long line from the garage to your hobby room, so technically you don’t need a regulator… but the last thing you want to do is run to the garage every time you want to adjust the pressure. Instead, set the compressor to the max pressure your airbrush can handle and add a regulator in your hobby room.


The next post is going to look at practical examples of how to use some of these in-line devices.

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Take a look at the Wargaming Tradecraft Techniques Page for links to the entire Airbrushing series and other tips, tutorials and information.

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