We had a similar problem on our 2010 Jayco 5ver. I found the lower water fitting on the hot water heater tank was leaking. It was just a drip about every 30-60 seconds. The pipe fitting was plastic and couldn't be screwed in any further because it was a straight pipe thread fitting. I replaced it with a brass tapered pipe fitting with some pipe dope on it. Cured the problem. Fortunately I caught my leak before any damage was done.
One other issue I have found early on is that not all of the threaded drain fittings were as tight as they should have been and they got even looser over time. I assume from being towed down the road. Once I went to winterize the rig and as I was running the RV anti-freeze into the kitchen sink it was running out of the sink drain onto the floor and out on to the ground through joint between the side wall and floor. Now at least twice a year I check ALL threaded drain fittings to make sure they are tight.