The remaining half bucket of the water dispenser will leak, and the full bucket will not leak. What happened?

I have encountered such a problem. After looking for the reason for several days, I finally found the reason. At first, it was thought that there was a crack in the bucket, and the gas entered from the crack and overflowed from the gap below the bucket seat. Later, it was not all day, but when there was no one at home. Isn't that weird?

Leakage time: in summer, go out and close the window, and it is hot at home.

A full bucket leaks no, half a bucket leaks.

The difference between a full bucket and a half bucket is that there is more gas and less water.

In fact, another problem is temperature, and the other is the pressure in the barrel;

Because of the change of temperature, the pressure in the barrel changes; Overflow usually occurs when the indoor temperature is high. With the increase of indoor temperature, other pressures in the bucket become larger, and the pressure pushes the water in the bucket outward. But at this time, the water outlet is well sealed, and the gap between the water storage bucket and the bucket seat flows out.