today at the pool

 today at the pool,  I'm thinking about Plumbing. And wondering how on Earth, unless there was a horrible cataclysm, that children who grew up with plumbing would lose that skill. Unless there was an unimaginable level of death, certainly the rich people would have retained it.     With only a few With only a few examples of Plumbing in existence, and if you crafty people, who aren't fighting for their lives, the technology would have continued, no question.    Why build Versailles if you don't have Plumbing? I don't get it.