Sounds like a reasonable solution to me. I would use the hex head self tapping sheet metal screws.

I would take something with a couple hooks (like a tow strap to tow cars for instance) and hook it onto opposing sides of the pipe and pull some pressure on it to see if I could pull the pipe up any. I would be surprised if you could, but if you can it means the glue totally failed. What I would be more inclined to believe is that the pipe slipped before the glue had totally done its job. PVC glue will sometimes do this if the joint is not held together till the joint sets. On that big of pipe I would imagine the glue used would be fairly slow set to give time to fully slide the joint together. But I am just speculating.

I have used the described screws to hold PCV pipe joints together that I wanted to take back apart (a mechanical joint, not a pressure capable sealed joint).

John

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