I got a custom plastic container that telescopes and is airtight to put a rifle in. It is great, and so long as I keep it out of the sun, it doesn't show signs of aging.

I've used gorilla glue on pvc pipe ends as well. You know, you can actually glue together two pieces of same diameter pipe with gorilla glue, and once it cures up completely, it is like you welded the pipe almost.

Keep in mind also that plastic pipe, especially pvc, will deform under pressure in time, so if you bury it, better to bury it in something that will take the load, otherwise it will go out of round or even collapse.