Of course you can shut off the water, but that mostly defeats the purpose of a surprise warrant and puts more people at risk because of the time involved sneaking around the plumbing. If you shut off an entire building, you are probably violating the warrant limitations specifically naming the place; and the rights of all the other residents.
People flush drugs and swallow drugs all the time to avoid being caught. I agree with you, usually small-ish quantities not kingpin size stashes. Doesn’t always work... they will find it in the pipes, bowls etc... and sometimes ends up killing the suspect via overdose.
Not at all. It’s a matter of timing and preparation. I used to live in an area where the cops staged for raids all the time. I don’t know why my street was safe but there were so many raid near but there it was. Every few months there’d be a ton of cops in battle gear and an evidence van and prisoner van. And they’d just be hanging around talking and then somebody would give the signal and boom off the went. So for these raids that included water cutoff it’s the same thing, so they all gather, guy turns off the water as everybody loads in, boom boom. Water is off for maybe 30 seconds before the bust hits.