Is it possible to do stress analysis of pvc lines. Even though we enter its properties ..the result represents the original case.

There are more topics in this forum about stress analysis of thermoplastic piping.
Personally I wouldn't do a stress analysis for them. Firstly because you have to do a short term and a long term analysis and secondly because due to (often) large deflection of the piping due to temperature differences your results will be not completely correct either.
All PVC suppliers have good engineering practice guidelines. Use those.