An apparatus has a hub including a water inlet for receiving source water, a water outlet for discharging ozonated water, and an interface between the water inlet and the water outlet. The apparatus also has a cartridge including an electrolytic cell for ozonating the source water. The electrolytic cell has a cathode, an anode comprising diamond, and a membrane between the cathode and the anode. The electrolytic cell is configured to flow source water through both the cathode and the anode. The cartridge further includes at least one cartridge port for removably coupling with the interface on the hub. The at least one cartridge port and the interface are configured to flow source water from the hub into the electrolytic cell and to flow ozonated water from the electrolytic cell into the hub.