Bathroom sinks (vanity) pipe size is 1.25 inches. It's a small hole too, so the strainer or stopper is specifically bathroom-sink-sized. Small = smaller than any other sink's hole (laundry tub, bar, kitchen, etc). The size is standard in the US and Canada (and maybe everywhere else too). Kitchen sinks have a 1.5 inch pipe. And a large size hole. A standard size. Bar sinks always have a 1.5 inch pipe. Bar sinks may or may not have a kitchen sink sized hole or a smaller hole. You can call a couple manufacturers like Franke and get them to guide you to the bar sinks that have small holes. Or... You can web search for bar sinks with small holes, but it is difficult. This is because search engines cannot figure out what to do with inches (or " ) and most manufacturers don't write inches in longhand form. There are more details to know, if you wish. Here are a few more. The pipe that comes out of the sink is called a sink tailpiece, and this can cause some confusion because the P trap also has a pipe coming out of it called a tailpiece (or, a P-trap tailpiece, to be explicit and precise). Also, the pipe that comes out of the sink is "tubular" and that is the one key word you need to use when you go a-web-searching. Plug these words into a search engine and see images showing pipes under a sink. E.g. tubular continuous outlet E.g. tubular end outlet After the P trap, the name of the pipe TYPE changes: it is DWV and no longer tubular. Wow. -- Bathroom sinks often have a pop up stopper or something. Kitchen sinks can have this but it's seldom seen. -- Bathroom strainers are good to catch hair. Hair does not decompose. Not fast. You want to remove hair manually instead of putting it down the drain because it just clogs the drain somewhere, unless you are lucky with the geometry of your drain. Bathroom sinks with a pop up stopper have a hair strainer inside, and one unscrews the thingie from time to time in order to remove the hair and gunk caught on the hair. -- If I had your two sinks I might install the sinks and have the stone overhang a lot. A bathroom is a lot cleaner than a kitchen: it's only skin cells and hair. So underneath the overhang there is no big splash of grease and compound organic rotting stuff. Even in a kitchen, a sink overhang is not a problem, for me. Stainless can be re-polished and this changes the surface which changes its characteristics and properties. The sinks may be repolished by any handyman. Or by you. If you get a stainless steel shop to mold you a two tier counter top they can weld these sinks into the counter and repolish them to suit the water bead test. I have in mind a two tier counter with a little swooping curve not a discontinuity. This might be good. It might to get water to flow off the upper part of the counter if your cats let water get anywhere. I know of cats that use a drain as a urinal and then rinse it out after use. Urine left stagnant in the P trap is bad for the pipe; it needs to be rinsed out or diluted a great deal. Hth

We had basically what looks like white yogurt that was almost filling our shower drain. I tried all of the commercial drain openers to no avail, including the slow-drain enzyme cleaners. Of course, I also tried vinegar, bleach, ammonia, and so on. (By the way... don't ever believe that combining vinegar and baking soda is a remedy to anything. It's a fun chemical reaction and seems like it's doing a crazy good job but what it's actually doing is nothing. Soda neutralized vinegar and basically turns it to water. So it's pointless.) Anyway, I had the same fear as many others have posted about what the rest of the pipes must contain. So I search around and found a couple references to the bio-slime, most of which didn't include a white version, but they seemed to be the closest resemblance to my drain problem. All of them talked about bacteria and fungus. You know what kills bacteria and fungus? Vitamin C. Yep. Otherwise known as ascorbic acid, you can buy it in powdered form and in various volumes. I thought it was worth a try so I ordered a 5 lb. bag for 30 bucks. You may be able to find it cheaper if you can find a non-consumable one somewhere. The process I tried was to wait until the water had drained after a shower and apply just enough to cover the white slimy stuff I could see and just let it sit there until the next shower. When I looked at it the next morning, I was happy to see that (even though it looked awful) the white stuff was turning yellow and drying out. So apparently this was killing it. I kept that process up for 4 more days. Toward the end of those days, I was adding a just a small amount of water so it would carry the powder down into the pipes. End result: It worked! I no longer have the white slime build-up. I only used about half of the 3 lb. bag so I'm ready if the blob attacks again!

A slow drain is first cousin to your next stopped up and overflow. It’s a partial clog and drain cleaner is useless. Drain chemicals are actually VERY DANGEROUS YO YOU. It will burn you. It will dissolve the heck out of marble tile Heck, it can eat the gloss right off of ceramic tile. It can eat holes in galvanized plumbing and make a bad situation much worse. It’s not really safe to use and should be taken off the market. That drain needs to be augured. You obviously aren’t up to the task. Pay a Pro. Or have the super do the job he gets paid to do. And you better darn well be sure that your insurance covers flooding from negligence. Because it probably won’t. And your neighbor is gonna have a 59K judgement against you for ruining his apartment. If you rent instead of own, you will be asked to leave. If you own, the super is going g to have the right to enter your apartment at will to inspect, because you were negligent in reporting issues that caused building damage. What kind of “home professional” are you? Dare we ask? CPA? Accountant? Masseuse? All three? It certainly doesn’t involve anything design or construction related, that’s for sure.

greg_2015, I'm really glad you got back to me on this. I'm not a plumber (obviously) but figured there had to be a different place where the plumbing is vented. But since I'm in a condo building and on the top floor, I did not want to take a chance and simply go ahead and cap the pipe. I even went as far as to consider that maybe the sink bowl holes are the vents, especially when I saw the black holes in the black pipe (see photo in my first post). After I got your response I went onto my deck, which gives me a clear view of the roof, and indeed saw what I consider to be the vent stack. By examining its location and the location of my kitchen and bathroom sinks, I could clearly see that the vent stack it right above the sinks. The photo below is of the vent stack. While standing on my deck I can touch the edge of the pitched roof with my hand. In fact, just below the photo is my deck door which leads into my kitchen. So the distance between the stack and me, from where I took the photo, is quite close. And here's a photo of the bathroom sink pipe after I capped it: By the way, something strange has happened. My kitchen sink clog seems to have gone away! This may have happened before I even capped the bathroom sink pipe. After I capped the bathroom sink I ran water down my kitchen sink which is on the other side of the wall from my bathroom sink. I was expecting to see the water back up into the kitchen sink. But no, the water kept draining away. Is it normal for some sink clogs to go away on their own after a number of days or weeks?