Abstract: A runner seal positioning system comprises an annular runner seal piston and an annular runner seal seated against the piston and mounted for rotation with respect to the piston. The runner seal and the piston allow a fluid leakage therebetween. A pressure supply extends to the piston for supplying a back pressure to force the piston against the runner seal to limit the fluid leakage. A weir box is provided, and a drain extends from the runner seal and the piston to the weir box for draining the fluid leakage into the weir box, so that the fluid level in the weir box is directly related to a rate of the fluid leakage. Pressure control componentry is operatively connected to the pressure supply and is responsive to the fluid level for automatically increasing the back pressure as the fluid level rises and automatically decreasing the back pressure as the fluid level falls.