Our New TT (May-2020) has a Electric/Propane water heater that has become very noisy lately. If only it were not right next to the bed. But it is and the 2' proximity with a very thin wall for seperat...
Did you ever describe the "noise"? If it is popping and crackling then I agree you need to flush it out. If is roaring like a jet taking off, follow Old-Biscuit's recommendation. Make sure it has cooled before you get your hand on that sleeve. Ask me how I know.