Exactly, at least one flush and more if you have 2 toilets. Or keep a bathtub full of water and plug the drain. As for shutting off the water, not sure you can do that so easily in apartment buildings. And either way the time it takes to do, the police are already basically announcing their presence by sneaking around the pipes or opening the street covers, leaving themselves exposed.
The drug problem is a demand problem not a supply problem; fighting the suppliers may be legal but it isn’t great public policy imo. Especially busting low level types. OK, flipping a low level dealer to find out the big importers might be a decent strategy... except when you bust down doors of a drug dealer you lose all leverage since everyone in the neighborhood knows the dealer got raided he isn’t going to turn rat.
Of course you can. When pipes get broken it’s vitally important to be able to turn off water. To apartments. To buildings. To neighborhoods. Can’t really fix pipes that are still active, water kind of gets in the way. No they didn’t announce themselves. For one thing they didn’t do it. That’s what the water department is for. Really guys, I don’t know why you’re so incredulous. It was common practice. Flushing was a non-issue. Still is a non-issue.