| 摘要 |
PROBLEM TO BE SOLVED: To prevent scientifically polluted outside air, an insect, and dust-dirt intruding from the pipe end by installing the water level environment opening- closing device of a water overflow port in an overflow pipe provided in a water storage tank of small exclusive water supply system. SOLUTION: This water level environment opening-closing device drains water (W2) by lifting lids by buoyancy of a floating ball 1 at emergency water level time, and the lids 5 and 6 are put in close contact on the water overflow port 7a by dead weight at ordinary time to thereby prevent the scientifically polluted outside air intruding from the pipe end 13 of the overflow pipe, and water W of the water storage tank is used to be supplied as life water suitable for public health.
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