The invention relates to family water saving system. It includes two high position water storage tanks. The first water storage tank position is higher than the second one. Water supply connecting tube is set between them. The input tube of the first water storage tank is connected to the first kind once water utilization installations water collection tank. The input tube of the second one is connected to the second kind. And its output tube is connected to the second kind secondary water utilization equipment. Each of the input tube is set submergible pump. The water saving system can use main family water utilization time after time according to different water utilization quality demand to reduce tap water using quantum and discharge amount to reduce cost and save water resources.