On my Big Horn I have one tank up at the higher level and all of the UDC, water pump, and lines run before the transition to the lower level. Open up the wall in your front storage to expose the service bay. This is also a good time to put hinges and latches on the wall for easy access. You can inspect the plumbing while under pressure for drip leaks. I hope you are using a pressure regulator. Not doing so will cause leaks. You can see the top of the insulation over the coroplast using a flashlight. Push on it using the handle of a long screwdriver so as to not damage it. If there is water you will know it. If it smells, it is gray water. If not fresh and can be form rain getting in or from your pumbing.