We are putting in a new sink and counter tops the sink will go under the counter. I noticed that the sink just has one hole for the faucet but no hole for the DishWasher Overflow valve, where does the overflow valve go? Will my plumber know? The counter tops are granite and so is the sink. Help Thanks in advance. CJ

Your plummer will know

That overflow valve is actually the air gap that prevents siphoning. Several plumbers have different opinions regarding the air gap verse a big, high loop in the drain line. Yes your plumber will know but if he is the kind of plumber who wants an air gap you should tell him long in advance. He would not necessarily have the tools to drill granite.