Spectra of the water lines and of the SiO(8–7) transition towards IRAS 17233–3606. In all Herschel spectra, the continuum level is divided by a factor of two to correct for the fact that HIFI operates in double-sideband. The red and blue lines mark the velocity range used for the modelling of the water emission (solid red: [+10,+39] km s^-1; dashed red: [+18] km s^-1; blue: [−30, −20] km s^-1, Sect. 4). The SiO(8–7) spectrum has a beam size of 18′′, similar to the 19′′ beam size of the 1113 GHz line, and it is observed at (4.̋7,0.̋0) from the Herschel , pointing. The dotted line marks the ambient velocity.