This paper shows reasonableness and application field of water power-control usage. We designed and constructed a proportional 4/3 directional continuous acting spool type sliding valve, a simplified model but still with the shape and working parameters resembling real valves. Our investigations of mentionedwater valve are divided on two different test rigs: real scale hydraulic test rig and tribological test rig. Taking into consideration the body accessible information about water power-control hydraulics (PCH), we constructed a simple, double, water and oil hydraulic test rig. We carried out preliminary tribological tests of different material-pairs lubricated with additive-free distilled water. The results of the preliminary tribological tests of different material pairs are described in this paper.