Multiple waste streams, including incompatible chemicals such as concentrated acids and/or strong base effluents, are handled together without the need for limiting or interrupting the processes run by the wafer processing tools. In some embodiments, waste tanks are primed with diluents, such as water, and a predetermined percentage of diluent is maintained in the waste tanks. In some embodiments, a diluent is flowed into the waste tanks concurrently with the waste pumping to generate a rinsing action for the waste tanks. Methods of the present disclosure accommodate both gravity type and vacuum type waste tanks.