We describe an extension of the Bell−Salt lattice model of water to the study of water confined in a slit pore. Wall−fluid interactions are chosen to be qualitatively representative of water interacting with a graphite surface. We have calculated the bulk vapor−liquid phase coexistence for the model through direct Monte Carlo simulations of the vapor−liquid interface. Adsorption and desorption isotherms in the slit pore were calculated using grand canonical ensemble Monte Carlo simulations. In addition, the thermodynamic conditions of vapor−liquid equilibrium for the confined fluid were determined. Our results are consistent with recent calculations for off-lattice models of confined water that show metastable vapor states of confined water persisting beyond the bulk saturation conditions, except for the narrowest pores. The results are similarly consistent with recent experiments on water adsorption in graphitized carbon black.