If it is what I think it is, it is an adaptation of a drum trap. They tend to clog up with deposits, hair, soak scum, etc. much more often than a standard p-trap. Do you have a link to a picture or description? My guess is that it is not accepted by US plumbing codes. I've seen them in Europe, but never took one apart to see exactly how it worked. Just wanted to verify we're talking the same thing.