US Patent 7819983 Dishwasher and controlling method thereof

A dishwasher and controlling method thereof are disclosed, by which noise generated from rotation of a passage switching valve can be reduced in a manner of adjusting a rotation timing point of the passage switching valve and a rotation speed of a wash pump. The embodiments describe rotating a passage switching valve for switching a passage to selectively supply water to either an upper nozzle or a lower nozzle and reducing a rotational speed of a wash pump supplying the water to the upper and lower nozzles before the rotation of the passage switching valve.