An improved method for the production of phenol, acetone and alpha-methyl styrene (AMS) from a cumene hydroperoxide and dimethylbenzyl alcohol (DMBA) mixture is described, wherein 0.5-5% additional water by weight is added prior to the final DMBA dehydration step, carried out in the presence of about 20-400 ppm mineral acid catalyst at 110-150° C. for 0.5 to 40 minutes residence time. The use of additional water allows greater flexibility in maintaining optimum temperature in the second stage over a much broader turndown range with fixed equipment, decreases the residual dicumyl peroxide (DCP) at the yield optimum for a given temperature, and increases the overall yield of AMS at optimum conditions at a given temperature.