UPDATE 2015-07-03 - I tightened the tolerances slightly for a better fit. Make sure your printer is well calibrated before printing.
Here are 4-Way and 5-Way Tees designed to fit 1/2" Schedule 40 PVC pipe. They are part of a series of 1/2" PVC fittings I'm designing to supplement conventional plumbing fittings.
I put the triangular holes in the pipes to help the glue dry. On the first iteration, I noticed that being air tight prohibited drying. The ledges on the top of the horizontal holes make it printable without support structures.
I will continue to add new fittings to the series and share them as a derivative of my original 3-Way Elbow. Please let me know if there is a fitting you need that I haven't created yet.
You are highly encouraged to make new derivatives. Please tag your new creations with #HalfInchPVCFittings.