Bathtub drain

I took the kids with me to church yesterday. When we got home, hubby announced he had fixed the bathtub drain. Yay! The problem we had with it was that the lever to hold the water in with hadn't been working at all. It wouldn't move. This is the only tub in the house, so when I learned that I couldn't take baths, I was not too happy. Anyway, when we had all gotten into the house, hubby said, "Everybody come into the bathroom so I can show you how this works." All four of us stood in there, looking at the new drain. It's one of those pull-up-and-twist types, and he said that it drains real fast (our old one took FOREVER to drain, sometimes hours). He said that if anyone wanted to take a bath ever, they'd have to make sure the water level NEVER gets within two inches of the round silver thing (he didn't call it that, but I don't know what it's called - it's the thing under the faucet) because, and get this, if the water touches and/or goes over the round silver thing, THE DOWNSTAIRS WILL FLOOD. Omg.