Since this sink doesn't come with overflow hole because it will build up bacteria the water will just go over to the floor and that would be a big mes

Hi Tracy, Thank you for your question. Our vanity top does not contain an overflow hole, the sink would simply drain slightly slower than a sink that has an overflow hole. As a leading manufacturer for baths sinks and vanity tops for the last 25 years, we have removed the overflow holes because it creates the opportunity for unwanted bacteria in the bathroom. Most overflows are designed so that they cannot be cleaned and, over time, will develop mold and mildew that usually will require the homeowner to change out their basin. With thousands of tops/sinks sold in the market today, our customers love not having the overflow/mildew issues. We can assure that all our sinks are IAPMO Approved to meet or exceed the national plumbing code. Our best recommendation would be for you to consult with your local Lowes Bath team member for the drain that will best fit your vanity top.