A flow regulator for regulating a flow rate of water within at least a section of a water system, such as an irrigation system, includes a base member and piston member. The piston member is movable relative to the base member and includes at least one notch through which water can flow when passing through the flow regulator. Movement of the piston member towards and away from the base member, respectively, decreases and increases an area of the notch through which water can flow. An orifice member detachably coupled to the piston member and having an orifice member aperture through which all water flowing through the flow regulator must pass limits the cross-sectional area of an interior water passage within the piston member.