CareHomeDeskCareHomeDeskTarget temperatures, monitoring points, and what to do when readings are out of range.
For Legionella control, hot water must be stored at a minimum of 60C and distributed so that it reaches at least 50C at all outlets within one minute. Cold water must be stored and distributed below 20C. These temperatures prevent Legionella from multiplying -- the bacterium grows most rapidly between 20C and 45C.
The calorifier (hot water storage cylinder) flow temperature must be at least 60C. Monthly monitoring at the calorifier flow and return is the minimum required. A calorifier return below 50C suggests inadequate heat-up or excessive heat loss and must be investigated. Calorifiers should also be thermally disinfected (pasteurised at 70C for one hour) at least annually.
Monthly temperature checks at a sample of hot and cold water outlets should be recorded. If a hot outlet fails to reach 50C within one minute, or a cold outlet exceeds 20C, this is an out-of-range result requiring immediate investigation and remedial action before the outlet is used again.
TMVs blend hot and cold water to a safe delivery temperature (typically 38-43C) at high-risk outlets such as showers and baths to prevent scalding. TMVs must be serviced annually and tested to confirm they fail safe (default to cold on failure). Do not confuse the TMV delivery temperature check with the Legionella temperature monitoring -- both are needed.
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