[AnthonyMouse]

That isn't actually removing anything, it's just spreading it around.

Removing dirt from the carpet and washing it down the drain is fine because ordinary "dirt" (i.e. soil) is made of non-toxic or biodegradable stuff. By contrast, washing toxic materials or heavy metals into the water table is the place you don't want them. There's a reason it's illegal to pour used motor oil down the drain.

[wizzwizz4]

And there are plenty of things it's legal to pour down the drain, but illegal to put in rivers, because it (grey water) needs treatment before release into the environment.