Reticulation of the sewage from Taupo township, New Zealand, proceeded in sages between 1974 and 1986, with initial stages servicing the central retail area and the streets closest to and parallel with the lake shore. Subsequent stages serviced streets further from the lake resulting in a progressive reduction in the volume of septic tank effluent entering the ground‐water table, but not necessarily a corresponding reduction in the nutrient concentrations entering Lake Taupo. The rate of reduction of the nutrient load in the ground water entering the lake was a function of the original load, and the proportion of the ground‐water recharge volume associated with the septic tank effluent water in each subcatchmenL An estimated reduction of 60% in the DIN load on Lake Taupo from this source has occurred between 1978 and 1989. Consequently, reticulation of the sewage from Taupo township has had a beneficial effect on the quality of the inshore waters of Lake Taupo along most of the foreshore.