When distillation is continuous, the boiling chamber should be emptied more often. Mineral scale buildup from hard water can be difficult to remove without the use of an acid-type cleaner. Commercial cleaning agents are available. The cleaners usually contain sulfamic acid or other organic acids. DO NOT use strong mineral acids like hydrochloric, sulfuric or nitric to clean distillers.
Strong acids can damage stainless steel and aluminum.
Check the owners manual or consult your local distiller dealer for the appropriate cleaner to use. Let the acid solution sit for the proper amount of time, then discard and rinse. An alternative cleaning agent is vinegar because it contains acetic acid, a weak organic acid. Let the unit sit over night, then discard and rinse. If mineral scale is still present, increase the vinegar concentration or cleaning time.