About all you can do is trace out the tubing and try to find the leaking connectors. Press in on the ring around the tube to release it from the connector. Then inspect the tube -- you may need to trim off about 1/4 inch -- and then make sure that the end is cut squarely and not pinched by the cutting. (Use a plastic tubing cutter, they pinch the tube less -- or use a very sharp razor or utility knife to make a square cut with a sawing motion to avoid pinching the tubing end.)

If the parts on the connector seem loose (I had a couple where the release ring had broken), then replace them.

Of course, you could, if you desire, replace the press-together connectors with some other kind that makes a stronger joint but the ones used are very widely used in RVs and other air pressure systems. However, they should not be used with the brake system!

On my coach, I had CCW switch the dump valves over from the main air system (I don't have an aux air compressor, only a Microphor 12v pancake compressor) to the Microphor compressor. Unfortunately, after the switch over, I discovered that there were air leaks in the dump valve system. As a temporary work around, I installed an on-off valve after the T connection where the tube goes to the dump valves. (So, I turn off the tube to the dump valves except when actually dumping the tanks.) When time allows, I'll search out the actual source of the leak and fix it -- but that tubing is behind panels in the utility connection bay and is not that easy to access.

I have a power switch in the bay with the compressor -- that I turn off when the coach is in storage. That stops the compressor from cycling needlessly.