Adding calcium only works for some, calcium morphinate is only soluble at a very narrow pH range, for most people it will cause some of the morphine to become insoluble due to the pH of their water, overall it is better to leave it out unless you have a good pH meter. Also, always start out with COLD water and bring it up to a boil, hot tap water has all sorts of nasty salts and hard water stuff in it that accumulates on the sides and bottom of your hot water heater.