The PTS is used to separate water from fuel. The fuel to be cleaned flows radially from the inside out through the coalescing filter elements. The inner layer carries out the filtration, while the outer layer made of hydrophilic material transforms the finest water droplets into drops of approx. 3 mm. These then sink into the water collection dome. The separator element at the outlet of the pressure vessel retains any tiny water droplets that may remain in the fuel.