Troubleshoot water leak

[KathyO]

HI all, long time stalker, first post. I could use some advice. It looks like the Florida freeze got me. I have a leak underneath. I had hoped it was condensation, but it stops when water is off. No signs of interior dampness. It runs down the center seam of the belly pan. It starts under the axles to the back. It drips when I turn the water on without using any faucets.
What is the best way to troubleshoot? I understand removing the belly pan is difficult. Should I remove the center rivets first? Will it allow enough room to possibly see the leak?
TIA

[Lumatic]

Are you talking about when you are hooked up to city water or using your freshwater tank or both?

Have you traced the water lines to look for leaks?

Do you have the original copper plumbing?

You can use a scope with a flexible shaft to peek into the belly pan without removing it.

[KathyO]

Yes. Hooked up to city water. I have no tanks on this one.
I have original copper. The city water line runs outside the belly pan and comes in at the front street side where it splits for the fresh tank that was under the gaucho.
I've checked all inside pipe and the flooring where I can't get to the pipe itself. I can't figure out where it would go back under the floor. On a 1960 Overlander would it go back under the floor around the axles? It looks like all plumbing runs inside, but there are no leaks inside. Soaked belly pan where I can reach from the back. AS is perfectly level. I just double checked that.
Scope! Thank you that is a wonderful idea.