A method for reducing effluent buildup in a pumping exhaust system of a substrate processing system includes, during a substrate treatment process, arranging a substrate on a substrate support in a processing chamber; supplying one or more process gases to the processing chamber; supplying an inert dilution gas at a first flow rate to the pumping exhaust system; performing the substrate treatment process on the substrate in the processing chamber; evacuating reactants from the processing chamber using the pumping exhaust system. The method includes, after the substrate treatment process, supplying cleaning plasma including cleaning gas in the processing chamber during a cleaning process; and supplying the inert dilution gas at a second flow rate that is less than the first flow rate to the pumping exhaust system during the cleaning process.