METHOD FOR PURIFYING AND FEEDING RAW WATER

PROBLEM TO BE SOLVED: To provide a method for purifying and feeding raw water, which combines automatic feeding of raw water from an absorption tank, and natural feeding of rainwater on a roof floor. SOLUTION: A purifying device for use in the method, is a combination of a filter 4 and a cyclone 5, and has a bypassing automatic valve 6 and a backwash automatic valve 7. In automatic feeding of water, an intake pump 3 and the automatic valves 6, 7 are interlocked to each other, and feeding operation is automatically controlled between feedwater levels a, b, to thereby purify and feed water. In backwashing, the backwash automatic valve 7 is activated upon stoppage of the intake pump 3, and the valve 7 is restored based on a timer. In natural feeding of water, rainwater stored on the roof floor is introduced into the cyclone 5, and sand, dust, etc., are removed from the water, followed by feeding the rainwater via the bypass automatic valve 6 into a feedwater tank 8. Surplus water is introduced into an intake tank 2. The intake tank 2 stores introduced raw water therein, prevents backflow of water, sets an overblow 10 at the highest location, and stores rainwater therein, to thereby serve as a water storage tank. By virtue of this method, ground subsidence due to conventional pumping of groundwater can be suppressed, and use of rainwater contributes to relaxation of contamination of a filtering agent and saving of water and electric power, etc. Especially, natural feeding of water is free from an influence of power failure due to a typhoon.