Forgot to empty hot water tank…

[John From Detroit]

To those who know more, why does the OP's leak only show up when the tank is on and the water is hot, but not cold? That's what I find real confusing.

Some heaters have a check valve on the inlet. Increased pressure due to expansion of the water from heating.

Also expansion of the tank due to heat makes the hole bigger.

 

[Yavne]

Some heaters have a check valve on the inlet. Increased pressure due to expansion of the water from heating.

Also expansion of the tank due to heat makes the hole bigger.

Where can I find it "check valve on the inlet"?