Anyone who heard yesterday of the young girl eviscerated/disemboweled by the main drain in a kiddie pool (a kiddie pool, mind you), I'm sure, has heartfelt empathy for the girl and her family, and perhaps some wonder a bit about the safety of their own main drain.

Some months ago I posted a question asking what the purpose of a main drain was and, not getting a response, I figured it was a dense question for what purpose could a main drain have other than to, well, drain the pool? I have yet to replace the liner in my inherited pool of five years now, but my guess is that when I do, that main drain is configured with PVC to take the water into the groundwater system?

Are the main drains in commercial pools different? Are there pumping systems located beneath them such that it was not the gravity of water alone that caused this horrific accident, unlike the drains in our pools where the pumps are geographically removed and have no connection to that drain? Otherwise, how could the limited water in a kiddie pool create such a powerful vortex to do what it did? (And on an entirely other subject, why in hell's name haven't they covers that are so fiercely bolted down they cannot possibly come loose, and in fact, require a diver with wrenches to open?)

If the screws beneath the grate of my main drain came loose, and I were swimming along the floor of the deep end (or floating on a raft overhead), would I be sucked flush with that grate by the forces of exiting water and drown?

What can anyone tell us about main drains, their function, and if commercial drains differ from residential drains?