Abstract: A high pressure water control device comprising a water inlet, a high pressure water outlet, a low pressure water outlet and a valve for selectively communicating the inlet with one or other of the outlets. The valve is a spool valve comprising a sleeve and a spool slidable in the sleeve. The spool has two axially spaced apart annular seals and the sleeve includes an annular groove in its outer surface and one or more dump ports which communicate between the groove and the inside of the sleeve so that when the dump ports are disposed between the spaced apart seals of the spool high pressure water will be delivered to the high pressure water outlet. The control device is in the form of a water gun having an elongate nozzle terminating in the high pressure outlet and a barrel surrounding the nozzle and terminating in the low pressure outlet.

Abstract: A high pressure water control device comprising a water inlet, a high pressure water outlet, a low pressure water outlet and a valve for selectively communicating the inlet with one or other of the outlets. The valve is a spool valve comprising a sleeve and a spool slidable in the sleeve. The spool has two axially spaced apart annular seals and the sleeve includes an annular groove in its outer surface and one or more dump ports which communicate between the groove and the inside of the sleeve so that when the dump ports are disposed between the spaced apart seals of the spool high pressure water will he delivered to the high pressure water outlet. The control device is in the form of a water gun having an elongate nozzle terminating in the high pressure outlet and a barrel surrounding the nozzle and terminating in the low pressure outlet.

Abstract: An energy recovery device includes at least one cylinder, a piston slidable in the cylinder, a first valve for selectively connecting one end of the cylinder to waste liquid at a first relatively high pressure and to drain and a second valve for allowing feed liquid to enter the other end of the cylinder at a second lower pressure via a feed liquid entry port and to be discharged via a feed liquid discharge port from the other end of the cylinder in response to movement of the piston caused by waste liquid entering the one end of the cylinder. A rod which extends from the other end of the cylinder and into but not through the piston, ensures that the area of the piston acting on the feed liquid is less than the area of the piston acted upon by the waste liquid so that the piston acts as a pressure intensifier to discharge feed liquid through the feed liquid discharge port at a higher pressure than the pressure of waste liquid entering the one end of the cylinder.