To reduce field work by preparing piping design, conventionally done at a laying site, with CAD based on a site plan and a foundation plan in order to enable adjustment of necessary members in advance and their dimension, in a piping method for a hot water floor heater designed to embed into a newly built multiple dwelling house and the like and a supply/drain twin piping member used therefor.

Supplying and discharging soft pipes are disposed in parallel so that two covering resin tubes 2A, 2B formed in a tubular shape with soft heat insulating material on each outer periphery thereof are joined with each other at their side belly parts, and at its joining part a signal line 3 is fixed along the tubes 2A, 2B. This enables the advance dimensional adjustment by performing the piping design with CAD design based on the site plan and the foundation plan that allows for immediate start of piping and connecting.