Camping World and other RV Supply sources sell "RV Valterra Detect-A-Leak", which is actually nothing more than a concentrated kids "Bubble Blowing" solution!
SealTech is the commercial company that does this for a fee...a lot of RV dealers offer it for $100.00 and up.
To DIY, the solution is sprayed over the top of the slideout roof/seal area while blowing air into the RV to pressurize it using a leaf blower or vaccuum cleaner. Bubbles will appear where the leak is coming from on the exterior.
You can find the proceedure here if you search the older forums.
Turn on the Bubbles!
