The effect of water on the kinetics of the liquid-phase dehydration of 1-pentanol to di-n-pentyl ether (DNPE) and water over Amberlyst 70 is revisited. To explain the strong inhibitor effect of water, two approaches were compared. First, a model stemming from a Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism was used, wherein the inhibitor effect of water was explained by the competitive adsorption of water and pentanol. Second, a modified Eley-Rideal (ER) model was used that includes an inhibition factor, in which a Freundlich-like function is used to explain the inhibitor effect of water by blocking the access of pentanol to the active centers. Both models fitted data quite well, although the best results were obtained with the modified ER model. The activation energy was 118.7 ± 0.2 kJ/mol for the LHHW model and 114.0 ± 0.1 kJ/mol for the modified ER one.