A hydraulic line balance manifold includes a housing having first and second open ports for fluidly coupling an upper open line to a downhole tool, first and second close ports for fluidly coupling an upper close line to the downhole tool, and bypass channel for fluidly coupling the second open port with the second close port according to pressure within the upper open line and the upper close line. A sensor piston having first and second positions relative to the housing is slidably disposed within the housing, the second open port fluidly uncoupled from the second close port through the bypass channel when the sensor piston is in the first position, second open port fluidly coupled to the second close port through the bypass channel when the piston is in the second position for reducing fluid resistance to mechanical operation of the slave valve in a mechanical override intervention operation.