First off, to those who think the clipping tool is the work of the devil...DONT CONTINUE

ok, now that that is settled, those of you still here will be learnning how to make three types of pipe junctions.

First, the 90degree pipe junction(old way). to create this junction you will first create 2 identicle cylinders, one horizontal, one verticle. make the ends of these cylinders overlap like this.


then simply make a 45degree cut using the clipping tool on the overlapped ends of each pipe like this.


ok, next is the 45degree diagonal pipe junction(first attempt). to create this we will again need 2 cylinders one verticle, and one horizontal, but this time we want to offset the ends instead of overlapping them...like this


now you'll want to duplicate either the verticle or horizontal cylinder and place it at the end of your duplicated cylinder like this(i did horizontal)


next you'll select your duplicated cylinder, doubleclick so your on the "shear" mode and shear the cylinder into the end of the verticle cylinder, or vise versa...like this


lastly for this junction, you'll want to clip off the extra bit which is purtruding into the verticle cylinder like so...


ok, i know these both really dont look that good, but they get the job done...but if your still not satified, read on.

lastly we have the 45degree curving diagonal pipe junction(final product). to create this we will yet again make 2 cylinders, 1 horizontal, 1 verticle. offset these like the last pipe junction. this time you'll duplicate both the verticle, and horizontal cylinders, and set them at the ends of there respective cylinders, and overlap the duplicates like so...


now using your side view(x/z) you'll want to shear each duplicate so that the top left points meet like so...


lastly you'll want to cut off the excess parts using the clipping tool, select each duplicate and clip the end at a 45degree angle like so...


great, now you have three different pipe junctions, its up to you which you choose.