"Things go better with Coke"

I had this stubborn calcium buildup in the for'd head for some time.  Tried some of the usual stuff with limited success.  Then in a moment of inspiration I poured in a liter bottle of coke that was laying around after a party (our one marina kid wouldn't touch the stuff with a barge pole).   Left it there for a week while I was away and voila;

If you Google "toilet + coca cola" you will discover that I'm not the first to try it.  I just hope my through hull and hoses are intact.