An ice machine is a food-contact surface, and neglected units grow slime, mold, and scale. These answers cover cleaning frequency, filters, and how to keep ice safe. Primary source: U.S. Food and Drug Administration.
There is no single mandated interval, but FDA Food Code 4-602.11 requires that food-contact surfaces of equipment such as ice machines be cleaned at a frequency that precludes the accumulation of soil, mold, or slime. In practice, most manufacturers recommend a full deep clean and sanitize of the ice-contact components at least every six months, and many high-use or hard-water locations do it every three to four months. Follow your manufacturer's manual, and clean more often if you see any buildup.
Ice machines are dark, damp, and often warm around the head, an ideal environment for mold, yeast, and pink or black biofilm (slime). Airborne spores and sugars from a nearby kitchen settle on interior surfaces and multiply between cleanings. Because the ice itself is a food, this contamination can transfer directly to drinks. The fix is a full disassembly, cleaning, and sanitizing of the ice-contact parts on a regular schedule, as FDA Food Code 4-602.11 requires surfaces be kept free of such accumulation.
Scale is the chalky mineral deposit (mostly calcium and magnesium) left behind as water freezes and evaporates, and it is worse in hard-water areas. Scale reduces ice production, harms ice quality, and shelters bacteria and mold from sanitizer. Remove it with the nickel-safe ice-machine descaler or cleaner specified by your manufacturer, following the dilution and dwell-time directions, then rinse thoroughly and sanitize. Never substitute a random acid; using the wrong chemical can damage components and leave residues on a food-contact surface.
A water filter is not a food-code mandate, but manufacturers strongly recommend one because it reduces sediment and scale-forming minerals that shorten machine life and degrade ice. A filter cuts down descaling frequency and protects internal components. Filters are consumables: replace the cartridge on the manufacturer's schedule, commonly every six months, because a spent filter stops working and can itself harbor bacteria. Keep filter changes on the same maintenance calendar as your cleaning so neither gets missed.
Cleaning removes visible soil, scale, and biofilm using a descaler or ice-machine cleaner. Sanitizing then reduces microorganisms on the already-clean surface using an approved sanitizing solution at the correct concentration. Both steps are needed and in that order: sanitizer cannot penetrate scale or slime, so sanitizing a dirty machine does little. FDA Food Code 4-602.11 governs the cleaning frequency, and food-contact surfaces should be sanitized after cleaning. Always rinse between the cleaner and the sanitizer unless the product directions say otherwise.
No. During a deep clean you must discard the existing ice and take the machine out of service, because cleaning and descaling chemicals must never contact ice destined for guests. Empty the bin, clean and sanitize the ice-contact surfaces and the storage bin, rinse thoroughly, and only return the machine to service once it is producing fresh ice on a sanitized surface. Plan the cleaning for a low-demand period and, if needed, arrange backup ice so service is not interrupted.