Abstract: A method and an apparatus for liquid supply use a pressure tank and a plurality of pumps. When the pressure or liquid quantity in the pressure tank has decreased below a predetermined level, a preceding or regular pump starts. When the demand is too large for this pump, another pump in standby position starts, too. The regular pump continues running for a predetermined period of time after the start, even if the pressure or liquid quantity in the pressure tank has returned to a predetermined level, whereas the standby comes to a stop upon such recovery. In this manner the frequency of starting the pumps is minimized so as to avoid overheating of pump-driving motors and reduce the power consumption.