Top and middle panels: comparison between the observed water intensities and the different models in Table 2, for R4-LV (top), R4-HV (middle) and B2 (bottom). The intensities predicted by the models have been corrected for the relative predicted filling factors. The given errors include 20% of calibration error. The triangles represent the models derived from H₂O and the squares from the SiO. Bottom panel: same comparison as the top panels, but for B2. The upper limit of the non-detected H₂O line at 1097 GHz is also shown for each model.