To reduce the quantity of work and to streamline packing and conveying work when the same portable piping units are employed for construction in the case where piping routes for water/hot water supply facilities are the same or symmetrical as in multiple dwelling houses and accommodations.

When a flexible portable piping unit is to be manufactured in a factory so as to correspond to a location of a connecting terminal at the construction site beforehand, a pair of right and left main pipes 41, 41 are disposed. Then, branch pipes 42A, 42B, 42C,... each having approximately twice a predetermined length are connected to the respective main pipes 41, 41, to thereby integrally form a piping unit 40A for two houses.