H₂O lines observed in Zw 049.057 with PACS. The black histograms are the observed, continuum-normalized, spectra. Model results from Sect. 3 are also included. The blue curve denotes the model for C_core, which was constrained using the high-lying H₂O lines detected with PACS. The light-blue curve denotes the model for C_outer, which was constrained using the H₂O lines detected with SPIRE. The red curve denotes the sum of these two models.