US Patent 7704040 Water pump

A water pump includes an impeller provided on an end of a rotational shaft supported on a body through a bearing, a mechanical seal provided between the impeller and the bearing, a draining hole guiding a coolant leaked from the impeller side to a reservoir provided at a bottom of the body via the mechanical seal, a vapor outlet provided above the reservoir for establishing communication between the reservoir and the atmosphere, and the draining hole opening to the reservoir at a lower level than the vapor outlet. An axis of the reservoir is offset from a vertical plane which passes through an axis of the rotational shaft.