Abstract: A cylinder and piston assembly for a retracting sprinkler head is buried well below ground surface of an area to be irrigated. The piston has an elongated, tubular sprinkler riser pipe extending upwardly from an upright cylinder having upper and lower water supply ports. The piston and the riser pipe are forced upwardly by water under pressure supplied to the cylinder through the lower water port. The piston is of annular configuration and is reciprocally movable relative to the lower end of the riser pipe between upper and lower stops secured to the riser pipe within the cylinder. A coil spring is compressed between the piston and the upper stop to urge the piston downwardly into sealing engagement against the lower stop, thereby isolating a radial port in the wall of the riser pipe from water under pressure at the lower end of the cylinder. As water enters the lower end of the cylinder the piston and riser pipe are raised together until the upper stop reaches the upper end of the cylinder.