White vinegar to the rescue
I recently bought myself a water distiller (tired of buying bottled water, and refuse to drink tap water) and the boiling chamber has to be cleaned of residues every few weeks. I had been using a cleaner from the company I bought the distiller from, which has several caution statements on the label, but after reading this thread, I remembered something about white vinegar being good for removing mineral deposits, so last cleaning, I poured some in and let it sit about the same amount of time as the other cleanser. It got rid of all the residue, even better than the more toxic cleaner does!