Firmly Plug Overflow Vent Or Double Drain With Rubber Stopper Or Damp Sponge Or Cloth.This Must Be Done In Order To Prevent Backsplash. Insert Pressure Plunger Nozzle Firmly Into Drain Opening. With Nozzle In Drain Add At Least 4 Inches Of Water In Sink Tub Or Basin. Quickly Shift Nozzle From Drain To Water While Pulling Back On Handle To Fill Pressure Plunger With Water. Reinsert Nozzle Immediately Into Drain. Make Sure Water Level Is Still Above Drain.Holding Pressure Plunger