So I have an old cast iron main stack which appears to be slowly eroding in the middle. The ends are solid, but for some reason the middle just isn't looking copacetic. I was thinking of getting some PVC that would fit around the pipe the whole length and cutting it down the middle. Then wrap it around, glue it back up (PVC glue for the pipe itself, Loctite on the ends), and give it all a fresh coat of paint. Any plumbers or those with plumbing experience can say whether this is a bad idea or not? Been living in my house for 10 years, no plans to go anywhere.