Compression fittings are similar to PTC fittings in a way that they both adapt the airline onto an air tank or other component. So how do these work? Compression fittings use a compression nut to secure the air line to the barb-shaped piece in the center of the fitting. For this to seal properly, the line has to be cut flush so that it fully seats over the barb. Below is an example of a good and bad cut.

The bad cut example shows how the line sits when you press it over the fitting. Half of the line at a minimum is not over the barb, and air will leak out of this connection if left this way.

The good cut example shows how the air line fully seals around the barb fitting when pressed onto the fitting. It is imperative that the line is cut flush and straight for the best seal. A poor cut will not only lead to an air leak, but when you honk the horn it will not sound nearly as good.

Bad Cut ❌

Good Cut ✔

*Using the included tube cutter that came with your kit is a surefire way to ensure a proper cut. The blade is sharp enough to cleanly cut the line, and you just need to line it up within the cutter.

Connecting the Line

Step 1: Remove the compression nut from the fitting by rotating it counter clockwise.

Step 2: Slide the line through the nut, so that the threaded portion of the nut faces back towards the compression fitting.

Step 3: Slide the air line over the barb fitting and move it back and forth to fully seat it over the barb. Check each side of the fitting to ensure the line is evenly seated around the barb. Slide the nut back down to the compression fitting and thread it back over the compression fitting. Use a wrench to tighten down once finger-tight.

Step 4: Confirm the line is secure by giving it a light pull outwards. It should not come off or break loose. If it does, remove the nut, and re-seat the line over the barb. Hold it in place while tightening the nut down.

Having Trouble?

In some cases, the air line you receive may be really stiff and seemingly impossible to seat over these fittings. If this is happening to you, the line can be softened by heating it up. Don't over-heat it, as the line will begin to melt at a certain point. You can use a heat gun to soften the end of the line, or leave it out in the sun for a few hours on a hot day. If you live in a cold area, the weather will only exacerbate the problem. Keep the line indoors and warm it up with a heat gun, or even a hairdryer. Once seated, the stiffness of the line will ensure it does not come off on it's own.