PURPOSE: To take early countermeasure against a location on trouble by providing a timing device to a storage pump operated by the signal of a water level detector and stopping the storage pump by at least one signal of the timing devide or the water level detector.

CONSTITUTION: An upper-limit water level detector 10 and a lower-limit water level detector 11 composed of a common electrode body 9, an upper-limit elec trode body 8 and a lower-limit electrode body 7 are constitution into a water tank 11 installed at a high position, which is disposed onto the roof of a housing, and the signals of the detectors 10 and 11 are input to a control panel 5 control ling a storage pump 3 through a signal conductor 13. A timing device 6 detecting the operation timing of the pump 3 is connected to the panel 5. When a water level exceeds an upper-limit water level by the trouble etc. of a pump operating relay and the detector 11 or when the pump 3 is worked for a fixed time or more by the trouble etc. of the pump 3, a control signal is output fro the device 6 tot he panel 5, and the pump 3 is stopped. Accordingly, an early countermea sure to the location of the trouble is enabled.