Hot water cylinder boils
Listed under: water heating, hot water cylinders, Services
Cause
Thermostat setting is too high
Repair
- reset the thermostat to 60°C. Stored hot water should reach no less than 60°C to avoid the growth of Legionella bacteria. However, the delivery temperature of hot water to sanitary fixtures used for personal hygiene in housing such as baths, showers and hand basins must be no more than 50°C. (The maximum was reduced from 55°C when G12/AS1 was amended in November 2023, with a 12-month transition period.)
Cause
Faulty thermostat
Repair
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turn the cylinder off
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homeowners are permitted to remove and replace a water heater thermostat so long as it does not involve work on a switchboard. (The details are in the Electricity Act 1992 sections 79 and 80, and NZECP 51:2004 New Zealand Electrical Code of Practice for Homeowner/Occupier’s Electrical Wiring Work in Domestic Installations.) Landlords/ business owners cannot carry out electrical work in their rental properties or workplaces unless they hold the relevant licence
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homeowners should only make this repair themselves if they have the skills, experience and tools to be able to safely and competently complete the job. You are required by law to carry out the work “in a workmanlike manner” and in compliance with all the relevant laws and codes
• most homeowners should call a licensed plumber to replace a faulty thermostat