Abstract: Water treatment apparatus for supplying ozonated water to appliances, such as clothes washing machines. First and second water aspirators include respective first and second Venturi tubes. One aspirator is designed for a relatively higher water flow rate, and the other is designed for a relatively lower water flow rate. A valve selectively directs water from a water inlet to a water outlet through either the first or the second water aspirator. Ozone from an ozone generator is drawn either into water flowing through the first Venturi tube or water flowing through the second Venturi tube, depending on the position of the valve. A water flow sensor includes a microphone physically connected for sensing a sound characteristic of operation of a Venturi tube. A controller effects a time delay for maintaining activation of the ozone generator for a predetermined time duration even after water flow has ceased.