[Dan Richardson]

Often plummers that need to run pvc on the oustide the house will cover the pvc coat the pvc with some sort of plastic polymer. The reason being is so that the pvc is not as exposed to the sun. Additional reason it adds additional support.

But the glue/resin as some have pointed out is important. I remember the "blue" pvc glue was rated for something like 180-200 psi max operating pressure.

When applying pvc glue make sure you are careful to first clean the ends of your pipe that you are applying. Bevel the edges slightly with paper or a file. Then proceed to place a thin layer on both the inside of the cap and the pvc you are using. When insert turn the pvc slightly, about a little less than a quarter of a turn.

Most important is beveling the edges and applying to both sides, often when cutting the pvc it becomes very sharp and jagged. There is often a lip on the edge and when inserting into a connector the bevel can push the glue out. So instead of an even gluing you have it bunched in certain spots. Not good for adhesive properties.