A modular header body is described for distributing fluid to an individually pumped fluid circuit. The modular header body has a valve to selectively isolate the header body's suction chamber from its volute, which permits a pump motor to be disconnected from the header body while the valve is closed. Each modular header body is constructed so that adjacent header bodies can be connected to each other to form a common suction chamber. Each header body's isolation valve operates independently so that the volute of one header body can be isolated from the common suction chamber without affecting fluid supply to the other header bodies.