A water treatment system including an automatic shut-off control valve. The network reach is further increased when on-line measured performance data are used for path selection and wavelength assignment. The aperture rate of the light receiving portion can be reduced without causing a sensitivity decrease and a change in spectral characteristics on the long wavelength side of the effective wavelength range. A heater element is arranged in each nozzle chamber to span the nozzle chamber and is connected to the drive circuitry to heat ink in the nozzle chamber received from the ink inlet passage. This structure is detected by the photodiodes, and the signals emitted by the photodiodes act on a controlling device. Alternatively, the gas released from the gas storage material can be guided to the first gas inletoutlet port and the second gas inletoutlet port through the gas-guiding channel.