Abstract: A chlorinator is provided for connection upstream of a pump in a swimming pool water recirculating system which includes a container for holding a supply of chlorinating liquid, a plurality of metering tubes having differing resistances to liquid flow extending into the container with their inlets immersed in the chlorinating liquid, and means for selectively connecting a selected one of the metering tubes to an outlet adapted to be connected to a swimming pool water circulating system. A pressure control valve may be provided between the metering tubes and the outlet and filler means may be provided at the metering tube inlets.