Backwater problem of hotel air energy water heater?

It should be that the hot water pipe on the first floor was taken over behind the main return valve.

It is suggested to carefully sort out the layout of all water system pipes and find out whether the hot water supply and return pipes on each floor are connected backwards.

As for the leakage of the water tank the next morning after the main backwater valve is opened, the biggest possibility is that a large number of backwaters replenish water at the same time, which causes the water in the water tank to overflow within a certain period of time. In this case, we can consider appropriately lowering the fixed position of the float switch in the water tank to leave more room for the water level to rise.