PLASTIC PIPE FITTING

PROBLEM TO BE SOLVED: To provide an anti-seismic pipe fitting made of plastics with which expansion/contraction and checking the separation can both be obtained compatibly. SOLUTION: The body 2 of pipe fitting into which two plastic pipes 1 are inserted, is configured so that a diametric enlarged part 23 of a socket inner surface is formed between a pipe end ridge 21 and an engaging ridge 22, that engagement with the outside surface 12 is generated at the time of normal water feeding therein so as to establish fixation of the positions of plastic pipes, and that a lock ring 3 is mounted slidably within a ring-shaped space S in the enlarged part 23 along with the pipes in case of emergency, for example in the event of an earthquake. According to this configuration, the lock ring is movable within the ring-shaped space freely while it bites into the outside surface of pipes, so that a margin for expansion and contraction to absorb an external force is assured. After the inter-pipe distance has expanded or contracted exceeding the specified limits, the side face of the lock ring 3 runs against the side face of the pipe end ridge 21 or engaging ridge 22, and a sufficient force for checking the separation will act.