Why does the hot water tilt out instantly when the hot water tap is turned on in the hotel?

The bathrooms in the hotel are all in back-to-back positions. The two rooms next door use a water supply pipe, and the upstairs and downstairs bathrooms are in corresponding positions. As long as someone has used hot water every few floors upstairs, your faucet is hot water. In the 1920s, Hilton hotels abroad began to use the back-to-back bathroom design, which saved the space occupied by water pipes and hot water. As for how the hot water comes from, I'm not sure. Some are municipal supplies, and some are hotel boilers.