pic: T Shirt Shooting Robot

[EricH]

The only thing I'm going to say to that is: You don't know what you're talking about, and you're comparing apples to oranges.

PVC is NOT used within houses. It's commonly used outside, underground, for irrigation systems. Note that irrigation systems are never used with air, unless they are being drained (and, in that case, they are left open at at least one point to release pressure). Also note that the ground will contain most catastrophic failures of reasonably sized PVC pipe. Within the house is always metal, often copper.

And no, PVC isn't used for sewers, either. I would guess that either that's ABS or it's a specialized pipe plastic. Again, note that sewers are underground and are often not pressurized (at all).

Note: in all of the cases you cited, the PVC is underground and used for liquids, not gasses. A T-shirt cannon is above ground and used for compressed gasses, which is a completely different case. If you're going to use parallel examples, then please use examples that are truly parallel.