A pump in desalination systems has four cylinders, each having a double acting piston. Each cylinder and piston defines a feed chamber and a recovery chamber. The pistons connect to a common drive. The connection to the common drive is such that the pistons reciprocate in a sequence equally spaced in time. Reciprocating valving for each piston is driven by the common drive to be 90 degrees out of phase with the respective piston. The valving connects the recovery chamber alternately to an inlet manifold for an intake stroke of the piston relative to the recovery chamber, and to an outlet manifold for a discharge stroke of the piston relative to the recovery chamber. A brief period of closure coincides with top dead centre and bottom dead centre of the piston, during which the recovery chamber is blocked off from both the inlet and outlet manifolds. The reciprocating valving is midway between its top dead centre and bottom dead centre during the period of closure.

Dispenser for dispensing a liquid, in particular a colorant for paint. The dispenser comprises a piston pump and a valve. The piston pump comprises a cylinder and a main piston reciprocatingly fitted inside the cylinder. The valve comprises a valve housing with a dispense opening (16), and a valve core within the valve housing. The valve core is rotatable and comprises a main channel and a secondary dispense channel with a smallest diameter which smaller than the smallest diameter of the main channel. The secondary dispense channel comprises an axial channel section communicating with the piston pump. A secondary piston fits reciprocatingly inside the axial channel section in the valve core.

Dispenser for dispensing a liquid, in particular a colorant for paint. The dispenser comprises a piston pump and a valve. The piston pump comprises a cylinder and a main piston reciprocatingly fitted inside the cylinder. The valve comprises a valve housing with a dispense opening (16), and a valve core within the valve housing. The valve core is rotatable and comprises a main channel and a secondary dispense channel with a smallest diameter which smaller than the smallest diameter of the main channel. The secondary dispense channel comprises an axial channel section communicating with the piston pump. A secondary piston fits reciprocatingly inside the axial channel section in the valve core.