Hot water stops flowing entirely despite the tank being full.
Small leaks can allow air to be sucked into the system even if water isn't leaking out. air lock in hot water tank
Disclaimer: This guide is for informational purposes. If you are unsure about any step or if your system is pressurized, please consult a certified plumber. Hot water stops flowing entirely despite the tank being full
For vented cylinders with a cold water tank: air lock in hot water tank