To provide a rainwater storage tank, which is lightened and simplified, the cost of which is reduced, which is enlarged easily and in which environmental load in the case of a disuse is decreased, and to enable various forms such as a ground installation, an underground installation, an upstair installation or the like even in an installation method.
A corrugated polyethylene or polypropylene pipe is used as the tank body of a water storage tank. The form of a corrugated form is formed in a trigonometric functional curved shape or a rectangular crease shape, and the size of the corrugated form is specified in 0.05≤/D≤0.20 and 0.07≤1/D≤0.30 when the height of the corrugated form is represented by (h), a pitch by 1 and the outside diameter of the pipe by D. Density is set from 0.930 to 0.980 in polyethylene.
YASUNO HIROSHI
ONO KEISOKU
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