| 摘要 |
<p>PURPOSE:To provide a drainage pipe which does not generate a large flowing noise of the drainage when the drainage flows therein. CONSTITUTION:A drainage pipe is made of at least three layers. An inner layer is a hard synthetic resin pipe 1. An intermediate layer is composed of a lead plate, a lead fiber 21, or a resin sheet including lead. An outer layer is composed of a metal pipe 3. The three layers are integrated to each other by drawing the metal pipe 3 as the outer layer.</p> |
