You should read the dilution sticky. Without diluting, chances are you will piss dirty. Obviously there is no way to tell 100%, but in all likelihood you will.

It sounds like we have similar smoking habits and this is my 10th day clean. I'm still fairly sure I'd fail a UA without diluting.

And yes, it does work. It's not a foolproof method, but it can work, especially if you've been clean for a bit.