Noisy water heater

[haiduan]

Our 5th season in our 2014 Vista 35B. We have a new noise coming from the water heater whenever we turn the hot on using any faucet. It's a fairly loud buzzing sound. I've accessed the heater by removing the drawer behind it in the kitchen. Nothing is leaking or appears to be vibrating. Everything is working, just have this new noise. Has anyone else exprienced this? Thoughts?

Thanks,
Andy Haiduck

[Old-Biscuit]

Check valve is 'chattering' due to scale
Winnebago likes to use 2 check valves....1 on cold inlet and 1 on hot outlet
Common nosy issue is with the one in HOT OUT
It is inside the nipple screwed into tank where hot line connects

Plastic junk.....plunger/spring/O-ring assembly.
Starts clogging up and chatters when you turn on hot water