RV's are trash. Ours is 2 years old and I had to replace the AC, "fix" the toilet which has a known problem and has been recalled, and replaced a broken leaf spring (fortunately it broke at the end of our 2 week, 2k mile trip as I was backing in the driveway). We bought the additional warranty and all of it requires a tech. They're typically $125 just for diagnosis which is not reimbursable by the warranty company. Plus there's a $100 deductible. So I'm in it for $225 before anything is fixed. New AC $169, new pair of leaf springs $148. Should have skipped buying the warranty all together. Such a waste.
Hopefully the new water heater works. We have a tablets like Mike mentioned. Works great by just setting the temp and turning on only the hot. Trying to set the temp with both knobs gets you scolded or frozen.