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Guide to Warewashing & Janitorial Equipment
How to Descale a dishwasher
Even the best-maintained dishmachine is vulnerable to one of the most stubborn
maintenance challenges in foodservice: limescale buildup. Caused by dissolved
minerals in water — primarily calcium and magnesium — scale forms when hard water
is heated, leaving behind white, chalky deposits on heating elements, spray arms, and
interior surfaces.
If not addressed, limescale:
• Reduces heating efficiency, forcing the booster heater to work harder
• Clogs spray jets, leading to uneven washing and failed sanitization
• Damages gaskets and seals, causing leaks
• Triggers service calls and unplanned downtime
• Voids warranties if manufacturers find excessive scale during service
The solution is regular descaling — also known as deliming — using approved
chemicals to dissolve and remove scale buildup.
When Should You Descale?
The frequency of descaling depends on your water hardness and usage volume:
Water Hardness (ppm)
Description
Suggested Descaling Frequency
0–60 ppm
Soft
Every 2–3 months
61–120 ppm
Moderate
Monthly
121–180 ppm
Hard
Every 2–4 weeks
180+ ppm
Very Hard
Weekly or install a softener
• Water hardness across Canada varies by region. Ontario, for example, often
ranges between 120–180 ppm.
• Use test strips or consult your RED Dealer to assess your local water profile
• Keep a descaling log sheet to track cleaning frequency and performance
• Combine descaling with weekly deep cleans for best results
• Use acid-safe plastic bristle brushes — avoid metal scrubbers that damage
surfaces
• For glass or visible components, vinegar can help remove minor film, but
commercial delimers are required for full-scale treatment
• For ventless machines, descaling should include heat exchanger tubing —
consult the manufacturer
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