An irrigation system comprises a casing 2 defining a chamber 3, the chamber having a water inlet 4 and a water outlet 5, the water inlet adapted to be connected in use to a water supply; a water control valve 8 within the chamber adapted to move between: an open position when the water level in the chamber is below a lower predetermined level; and a closed position when the water level in the chamber is at or above an upper predetermined level; an aperture 19 communicating between an interior and an exterior of the casing; a control member 15b movably located in the aperture and having an outer portion external to the casing and an inner portion 20 within the chamber; wherein application of an external force to the outer portion urges the inner portion between an engagement location in which the inner portion engages and urges the water control valve to an open position and a disengaged location in which the water control valve is free to move buoyantly to the closed position.
