Hi, there.Does anyone knows where to find a library for PVC pipes reducers,tee,elbow etc for autocad ?

Have you checked the CAD Blocks section of this website yet?Blocks/symbols only have to be saved in either DXF and/or DWG file format to be inserted into AutoCAD.  Check the version of AutoCAD that the blocks were created in too.Can we assume you are working in metric units?
John Connor2017-05-10 16:55:11

Thank you for answering me. I have already checked the site, but i didnt find anything, except one file with few pcv elbows, tees, reducers (file : PVC-FITTING-ELBOWS-TEE-REDUCERS.DWG), im using a metric units

Well there are other places that you can check.  One of them is the AUGI website.  You might get lucky and find something there.  But you will have to sign up first.There is also this app at the AutoDESK App Store....https://apps.autodesk.com/ACD/de/Detail/Index?id=5542906462405181104&appLang=en&os=Win32_64The symbols are metric.
John Connor2017-05-10 17:57:25

Put something like "free cad blocks" into a web browser Search window, and you'll get more sites than you can ever look at.  Most have categories, many have both 2D and 3D versions of things, etc., etc.  You should also look into manufacturers' websites.
Kent Cooper2017-05-11 16:26:39

Thanks everyone for helping me. I find the George Fisher AutoCAD Library useful