OK, this is ugly, but I'll share anyway. I wanted to improve vacuuming optimization, so I had my pool guy install a valve that would divert all suction to the vacuum port, and remove the skimmer from the equation. Worked great, but...
I unknowingly requested a potential danger! It's my understanding that a two-drain system is safer for two reasons: it halves the amount of suction to each drain, but the second reason is more important: should someone block one of the drains (loose suit or long hair, etc), the entrapment danger is lessoned by the other drain, which "takes over" the suction and reduces the suction at the clog. I'm not doing a great job of describing that, but hopefully making it somewhat clear.
By closing off all the intake sources save my vacuum port, if someone were to come into contact directly with it, there would be no other intake to take up the slack. The full force of the pump would be directed at the contact point, and nowhere else. I have heard stories of people being eviscerated in this way, and I suspect they are not just stories. There is a safety flap on my port that is supposed to protect against this possibility, but it is, after all, just a small spring-loaded piece of plastic.
The way my system is set up, it would take a lot to go wrong for something like that to happen, but the possibility exists and I haven't quite figured out how to safeguard it (except to undo what I altered).
Just sayin'... I think it's possible to create a real danger, however remote, by what one does with their pool plumbing...
