Abstract: A strainer includes a water collector on an upper side, and a tube coupled on the bottom of the water collector. The tube has flutes formed on the inner wall. An extendable rod is housed in the tube and has lugs on the periphery to slide in the flutes. A latch member is housed in a housing chamber on the bottom of the extendable rod and has coupling sections formed on the bottom in an annular manner. An elastic element has a top end housed in the latch member and a bottom end fastened to a coupling member to couple on the bottom end of the tube. The top end of the extendable rod is fastened to a plug which is insertable in the drain port of the water collector. A filter is located in the water collector and has a button in the center depressible up and down to control water collection or discharge.