PURPOSE: To use liquid disinfectant easily dilluted at required concentration and to attain an effective result a sanitary aspect without trouble such as calculation for preparing the dilluted liquid and replacement of disinfectant by mixing liquid disinfectant automatically diluted at specified concentration with city water when it is allowed to flow out and allowing the mixture to flow out.

CONSTITUTION: Detection of flow rate is performed by a gear type flow rate sensor 2 in the inside of an ejector 1. The detected result is outputted to a controlling circuit. A feed pump of liquid disinfectant must faithfully execute the feed rate by a command of the controlling circuit. Therefore the liquid chemical of accurate quantity is fed. A tubular pump is used so that the rotary part of the pump is not directly touched to the liquid chemical. Further the required concentration is set by an operation switch. The correlation of both the flow rate of water and the rpm of the motor for the pump is previously stored in the controlling circuit. When city water starts to flow, the flow rate is measured by the flow rate sensor 2. The pump of disinfectant is turned ON after measurement and rotated only at the set concentration of the operation switch and the calculated result of flow rate and stopped. thereafter it is repeatedly performed.