California Faucets’ ZeroDrain is a “pop-down” drain that sits flush with the sink and requires no lift knob to operate. A one-finger touch is all that is needed to “pop-down” the stopper into the closed position and allow water to fill the sink. It features a piston design for a perfect seal every time. Press it again to release it and the water disappears into the thin circular gap around the stopper. To clean, simply pull out the stopper, rinse and reinsert.