Why can the water heater turn on the hot water in the kitchen, but not the hot water in the bathroom

Check the water outlet of the hot water faucet, if it is small, it should be a problem caused by insufficient water flow. >>>More

You're talking about gas water heaters, right? Gas water heaters installed a long time ago did not have a mixing valve, and most of them relied on two valves to adjust the water temperature. Especially in winter, the amount of hot water required for bathing is large, and the hot water valve will be opened to the maximum, and basically the gas water heater will work at full load, causing resonance. >>>More

This is most likely a slight air leak in your gas water heater. >>>More

Your toilet and kitchen hot water pipes are not connected.

If there is hot water in other places, the kitchen is not far away from the water heater, and the hot water should come after a while. >>>More