An RCCB was installed when the flat underwent an upgrading programme in the early 2000s, but it only protected circuitry at the utility room and would not have interrupted electricity supply to the water heater, Mr Goh said.
It is also good practice for homeowners to regularly test their RCCB by pressing the test button monthly. Electricity supply in the premises should be completely cut off — if not, homeowners should engage a licensed electrical worker to rectify the problem, he added.