A steplessly adjustable hydraulic insert valve has a housing defining a radial direction and an end side in an installation direction. The invention includes a protective tubular sleeve, or insert cartridge in which the side ports are located to overlap with the intersection of axes of the inlet and outlet bores, but to avoid direct impingement of fluid along the axis of the inlet bore. With the toilet seat in its horizontal position, a downward force on the pedal produces a rotation of the first part of the torque transfer mechanism which produces an opposite rotation of the second part of the torque transfer mechanism causing the toilet seat to pivot to its raised position. In a preferred embodiment, spray drying is used to remove the solvents and the pore forming agent.