PURPOSE: To facilitate replacing and repairing of an existing pipe by enveloping a target part of a water distribution pipe with a seal casing cover, cutting in its inside two parts of the water distribution pipe, and further freezing it outside this cover.

CONSTITUTION: A seal casing cover 2 of two-part divided form is mounted from the outward in an objective part of a water distribution pipe 1 to coat the objective part. Next in the seal casing cover 2, by an oil cutter mounted in an introduced oil feed pipe, two parts with a suitable space apart of the water distribution pipe 1 are cut. Next in a cut part S of the water distribution pipe 1, a stop cock 4 of rubber quality is press fitted, to close the pipe. In both outer sides of the seal casing cover 2, water in the water distribution pipe 1 is frozen by using liquid nitrogen or the like, to function as a temporary gate valve. After ending replacement, repair, etc., of the pipe, the stop cock 4 is removed, to restore the water distribution pipe 1 to be communicated into an ordinary condition.