A reason why having two sinks, in a kitchen, is justified, is because hot meat and milk cleaned or mixed together in a single sink could constitute bishul; one of the three prohibitions of "לֹא-תְבַשֵּׁל גְּדִי, בַּחֲלֵב אִמּוֹ" (Shemot 23:19, 34:26, Deut. 14:21)
The hot water that arrives at one's sink comes from a boiler, which flows through pipes before it reaches your sink. Are there any opinions that suggest that pipes containing water constitute a kli sheini? The ramification being, that there could be no prohibition of cleaning/mixing hot meaty and milky items in a sink together (for those that hold that there is no bishul in a kli sheini, even when it is above yad soledet boh).