Rain water plant

System has a low pressure rain water tank with a minimum level detector, a pressure increasing pump for feeding water from the tank to tapping points and a drinking water tank from which water can be pumped to the tapping points if the rain water tank is empty. A pump in the line from the rain water tank to the pressure increasing pump is switched on with the pressure increasing pump and off by the detector if the level falls below a minimum. The system has a low pressure rain water tank (8) with a minimum level detector (7), a pressure increasing pump (3) for drawing water from the tank and feeding it to the tapping points (BW) and a drinking water tank from which water can be pumped to the tapping points if the rain water tank is empty. A pump (6) in the line (10) from the rain water tank to the pressure increasing pump is switched on in common with the pressure increasing pump and switched off by the detector if the level falls below a minimum level.