I think the Sink Twice idea has merits, but it does not seem that it is worth eighty dollars, especially since the warranty is apparently one year. You would need to flush the toilet (and wash your hands) over twenty-five times a day just to break even. Yes, standing over the toilet to wash your hands would be weird, but I am not sure how else to do it. I was surprised to read how many homes have a bathroom too small for a sink. I have never seen one. I guess situations like that require this, but how common is that?
Well, they have sold four thousand of these devices. I wonder at what point they would sell enough for the price to come down. It may not make financial sense, but I imagine there are many situations where early adopters make good things possible for the rest of us.
What if you used a T to hook up water that would flow into your sink to a small unit on your countertop, which then ran into the toilet? Yes, this would require the countertop space, although perhaps you could design something to attach to the end of your counter, or the wall, and you would not need to stand over your toilet. You could also design something more closely resembling a sink and not an inverted toilet lid. I wondered how much extra water a design like that would use, but if you designed something with six feet of quarter-inch tubing, it would hold less than two ounces, based on the math used here:
https://www.quora.com/How-much-liqui...-500-feet-long
If you used this enough to break even, you would use an extra 144 gallons.
A surprising number of people asked about brushing their teeth in this. Who brushes their teeth immediately after going to the bathroom, without washing their hands? You know what? I do not want to know, but they are concerned with brushing their teeth, but not about fecal hands?
Why would anyone do that if they had an actual sink? "I could use a normal sink like some weirdo, but I am going to bend over the toilet tank like a cool guy, flush the toilet, and now we are in business!"