Alma observation predictions to target water in HD 69830 showing the integrated flux in Jy km s⁻¹ for the o-H2O 10₂₉ − 9₃₆ transition at 321.22 GHz as a function of the temperature and the quantity of water. The black dashed line indicates the critical mass level when water starts self-shielding. The level at 0.012 Jykm s⁻¹ is for a signal-to-noise ratio of 5 represented by the solid white line labelled 5c. This line is rather sensitive to low amounts of water and may allow for the detection of the first water gas disk in the near future.