In an embodiment, a polycarbonate polymerization process comprises interfacially polymerizing a carbonate compound and dihydroxy compound in the presence of an interfacial catalyst to form a polycarbonate and adding a viscosity reducing agent and a transesterification catalyst to polycarbonate upstream of a first filter to form an adjusted polycarbonate. The first filter can be replaced with a replacement filter and the adjusted polycarbonate can be introduced to the replacement filter. The flow can be diverted to a replacement filter. The process further comprises reducing the addition rate of the viscosity reducing agent and the transesterification catalyst until the addition rate is 0 mol/hr.