Fresh waterline leaks

[Argosian]

I just bought a 1976 Argosy 28 motorhome; center twin with rear bath. Unfortunately the copper plumbing has numreous leaks. I've repaired the visible leaks but water still runs out the bottom from the belly pan, but it appears the water lines to the shower run around the back, below the bathroom sink and stay above the interior floor yet no water leaks into the interior. I don't have a compressor to pump air into the system to "listen" for where the leaks are. Do I need to drop the belly pan? Are there any water lines under the floor in the area of the gray and black water tanks? I have a reproduction of a 1978 owners manual, but no diagram for the plumbing system. Any help would be greatly appreciated. I'm competent enough to do the work on the plumbing but I don't know "what to tear up" to get at it. Thanks.

[HowieE]

There should not be any water lines under the floor. If the rig ever wintered in Idaho and has copper pipe I would consider a complete replacement. Copper does not winter well.

[Argosian]

Thank you for your reply. Im relieved to hear there are no water lines under the floor. The MH lived in Washington most of it's life but I bought it in Wyoming from someone who neglected it and I' sure that's where the leaks developed.
It seems like the leak may be behind the stool/shower plastic then. It's the only thing I can think of where it would leak but not make the interior wet.
Eventually I'll take your advise and change out the water lines, but I lost my job a couple of weeks ago and bought this to live in while trying to find work so I'm trying to not spend a lot of money right now.
Any other suggestions regarding where to look, or how to access unseen fresh water lines?

Thanks again.

[HowieE]

The easiest way to repair copper pipe is to use Sea Tech fittings and plastic pipe. As long as you can get to a Good Round section of the copper you can cut it out with a small tubing cutter and slip in the new section.

As for finding the leaks I would drain as much water as you can and try and get a compressed air source and apply about 35 lbs of air to the system. You should hear the leaks and hopefully be able to get to them.