When the condensing portion capacity is smaller than the boiling chamber capacity to produce steam, water will be lost as carry-over steam through the condensing unit. Periodic cleaning is required for all distillation equipment. Wasting water from the boiling chamber should reduce the frequency of cleaning but some precipitates will collect in even the best units. Because the precipitates interfere with heat transfer, they must be removed. The deposits are generally salts of calcium and magnesium but iron, manganese and many others may be included.
Acetic acid is the most common cleaner used in home stills.
Any strong acid would work, but acetic acid is much safer than most. Hydrochloric acid, for example, is very aggressive and so must be used with care. Manufacturers usually recommend a cleaning procedure, product and frequency for their equipment. Portable units typically have 500 to 700 watt heating elements and produce 3 or 4 gallons per day. The larger units have heating elements of 1,000 to 1,500 watts and produce 8 to 12 gallons per day.