Alas, something that can easily ruin my "casual plumbing" experience is when there's plaque in the pipes. For those who haven't messed around with pipes much, it's not uncommon for kitchen drains to get this plaque not unlike the stuff that builds up between your teeth. Alas, it's not just the yogurt-type of stuff that ends up due to bad flossing.
It's like.. it's like mildewy rubber that's starting to fall apart. Or like mold that's started to solidify into a stage just thicker than custard. And it smells exactly like halitosis, which is one of the smells that, although I'm not allergic to it, I can stand the very least. I'm now doing my best Lady MacBeth imitation, scrubbing my hands every five minutes since I'm positive I can still smell it on myself.