The booster pump system includes a base pump module and one or more expansion pump modules connected to the base pump module. Each pump module has suction and discharge manifolds extending between the pump module sides and at least one pump connected between the manifolds. The expansion pump module suction and discharge manifolds connect to the base pump module manifolds, respectively. The pump modules are bilaterally symmetrical such that either side may be connected to the piping system or to another pump module. A bypass module is connected between the pipes of the piping system. The size of the manifolds is larger than the size of pipes that would normally be used with a pump having the capacity of the pump to which the manifolds are connected. Pump modules are connected to each other and to the piping system by quick release connectors.