The purpose of this study was to examine whether any environmental benefits were obtained when the emptying of sludge from septic tanks were carried out with a dewatering technique using polymers compared to complete pump-out. The mean value of transport distance, fuel consumption, CO2 emissions and the weight of waste per septic tank emptying was calculated for each emptying method. For this, data on transport distance, fuel consumption, CO2 emissions per liter of fuel and number of emptied septic tanks were used. An energy audit over a sewage treatment plant was used to calculate the energy consumption for the treatment of the waste from the two emptying techniques. The environmental impact of the use of polymers and the returning of reject water to the septic tank was examined by studying the literature in the research field. The result showed that emptying with a dewatering technique compared to complete pump-out resulted in shorter transports, less fuel consumption, lower CO2 emissions, less waste and a lower energy consumption for waste treatment. The use of polymers in sludge dewatering should not have any adverse effects on aquatic organisms or health impacts if the dosage and the design of the treatment plant is correct. It is not established whether the return of reject water have any environmental effects. In conclusion this report shows that the emptying of septic tanks with a dewatering technique is better than complete pump-out from an environmental point of view.