Plan 14 is a combination of Plan 11 and Plan 13.  The flush comes from the pump discharge area to the seal then to the pump suction area.  Plan 14 is often used in vertical pumps to provide adequate flush flow and vapor pressure independent of the bushing in the pump.  It is also used in viscous products to provide a flow path out of the seal chamber in addition to flow through the throat bushing that can be restrictive.  Plan 14 is often combined with other piping plans, especially with dual seals, for example Plan 14/52.

By carefully sizing the orifices and throat bushing, Plan 14 can be used to adjust the seal chamber pressure.  For example, if the throat bushing clearance is relatively tight and the two orifices are the same diameter then the seal chamber pressure will be about midway between pump suction and discharge pressure.