Parametric library for generating any kind of planar pipe fittings. I'm using them for my plant-watering system, I guess it can also be used for aquariums, water-cooling etc.

Designed with OpenScad, source code there: https://github.com/bluesyann/openscad_shapes

From the code you can adapt these parameters to your pipes:

r: outer radius (mm) e: wall thickness (mm) l: fitting length (mm) b: ridge width (mm)