The age of the groundwater is an important parameter that plays a part in estimating the sustainability of the resource. This parameter is difficult to quantify, as samples (i.e., water wells) often contain a mixture of waters of different origins and residence times. Some tracers, such as radiogenic helium, have multiple sources that cannot be quantified. Here, we present the results of a study on water dating in a region near Montreal, Quebec. Four dating methods were compared: 3H-3He, 14C, U-Th/4He, and 234U/238U.