Prevent air leaking from couplings on an air compressor hose

Question

I recently purchased an air compressor. When I turn it on without a hose attached, it seems to work fine. It gets up to 140 PSI and shuts off the motor.

As soon as I attach the hose, I can't get it above 60 PSI. I can hear air leaking out both at the quick connect coupling to the air compressor and at the other end where I have an attachment screwed on the hose to fill car tires.

This is similar to the connection on the air compressor (except that the female end is permanently attached to the compressor such that I can't unscrew it):

I assume that Teflon tape on the threads would help the screw on connectors, but I'm at a loss as to how to make the quick connect couplers less leaky.

Answer 1

You are correct that it is a good idea to use teflon tape on the threaded fittings, however no sealant is required or advised on the quick-connect part itself. These are designed to seal using internal o-rings.

There are multiple types of quick-connect air line fittings that at first glance appear similar, but are not necessarily compatible. It is very likely that you have connected two incompatible types, resulting in a leak. This is very common.

The two "main" types are often referred to as "automotive" and "industrial", though each can have sub-types that are typically letter designations, e.g. Industrial can be M, H or G. There's also a type called ARO, and one called Lincoln, but these are somewhat less common (at least in the US consumer market).

(image from Legacy Manufacturing)

The documentation for your air compressor may specify exactly which type of fitting you have. Otherwise head to the local big box store with your male coupling that leaks, and look for a similar-while-slightly-different male coupler to try.

Legacy manufacturing has published a very informative guide on the evolution of the various types of quick-connect fittings that lists the common types in use, with some images of each.

Milton Industries has also published a document that may help identify the type of plug you have, though their letter designations may not exactly match those of other manufacturers.

Answer 2

If you do not get a fitting attached properly or it is incorrect in size, air will surely find it's way through. Sometimes, ensuring there is no built up pressure and using a strong hand is required for some tools as we can sometimes think we got the fitting on all the way when, in fact, we did not. On occasion, when airing my tires, if I was tired or wore out after a long day, I would hear air leaking out from the chuck and would thus realize I needed to use a little more strength/forward pressure with the chuck. Same when connecting a hose, sometimes you have to make sure you pull the attachment back all the way and keep it open until the relative parts are in place, flush and set, before you can make a good connection happen.

Answer 3

Placing an O-ring inside the socket will stop the leaking between the end and the quick connect. This will also allow you to use an industrial (type D) end with an automotive (type C) Quick Connect socket. It has worked for me many times in a pinch.

Answer 4

I bought my Campbell Hausfeld Professional Air Compressor, air hose, and fittings in 1995. 4.5 HP Electric Motor, and a 20 gallon tank. I used pipe dope on my fittings for my air tools, and for the air hoses. I have never had a leak.

Answer 5

If you got quick connect couplings at a big home improvement store there are different types. It might pay to change the one that is on the compressor to the others you purchased just to make sure they all match.

Answer 6

Hey did you try to tighten the quick coupling connector with a wrench?? That should work and some of the teflon tape. You should tighten all the connections with wrench.