Whether the solar panel is connected to the 5V water pump needs to be equipped with a regulator depends on the voltage match between the solar panel and the water pump. If the output voltage of the solar panel can be stabilized at about 5V, and matches the rated voltage of the pump, then it is usually not necessary to install additional regulators.
However, if the output voltage of the solar panel fluctuates greatly, or does not match the rated voltage of the pump, then in order to ensure the normal operation of the pump, it may be necessary to install a regulator to stabilize the voltage output. It is recommended to carefully check the technical parameters of the solar panel and water pump before wiring, and decide whether to install a regulator according to the actual situation. In addition, in order to ensure the security of the system, it is recommended to consult professionals or manufacturers.
No need for a pump the voltage requirement is not so high.