A man and his parents were electrocuted in 2020 in a case involving a water heater that had been installed in an unsafe manner, and on Friday (June 3), State Coroner Adam Nakhoda found the trio's deaths to be a misadventure.
The tragedy that took place in the elderly couple's HDB flat in Ho Ching Road in Jurong on Dec 10 that year claimed the lives of Mr Omar Abdul Manan, 80, his wife Asmah Bujang, 66, and their son Muhamad Ashikin Omar, 45.
On Friday, State Coroner Nakhoda noted that the model of the water heater in the case had been approved for use in Singapore.
Describing the case as a "truly tragic accident", he stressed that such appliances should be properly installed according to the specifications of manufacturers.
State Coroner Nakhoda said Mr Omar, who was found in the bathroom, was electrocuted when he was taking a shower.
Madam Asmah suffered a similar fate after she rushed in to help him.
Mr Ashikin, who arrived at the flat later, was also electrocuted when he tried to help his parents.
Following the tragedy, the elderly couple's daughter told investigators she did not know who had installed the water heater.
In an earlier proceeding, the court heard that a three-pin plug connected to an electrical socket had been used to supply power to the heater.
Senior associate engineer Goh Chin Fong from the Energy Market Authority testified in March that the heater should have been connected directly to a double-pole switch instead of a wall plug.
Mr Goh, who had given expert testimony, described a double-pole switch as one with an "on-off switch with an on-off light".
When investigators disassembled the water heater's three-pin plug, they found that the neutral and earth cables had fused together.
This caused the current to flow back to a heating tank in the water heater, energising a metallic hose connected to the tank.
Mr Goh said the cables in the three-pin plug could have fused together because of overloading.
A double-pole switch is safer as the cables are spaced further apart, minimising the risk of the cables fusing together.
The court heard that the water heater should have caused a power trip because of the electricity leakage, and this would have cut off power to the unit.
But when investigators checked the flat, they found that the residual current circuit breaker (RCCB) did not protect the main electricity circuit for the whole unit. Only the utility room was protected.
The elderly couple had lived in that flat since the 1970s. Back then, HDB homes were not installed with RCCBs, said Mr Goh.
He added that HDB installed the circuit breakers only from the 1980s, and an RCCB was added to the couple's home during an upgrading exercise about 30 years after they had moved in.
However, in their home, it protected only the utility room.
HDB flats in the 1970s also did not have double-pole switches, said Mr Goh in March, adding that it was because water heaters were not widely used then.
Investigation officer Mohamed Ariff Mohamed Khair testified in March that Mr Ashikin's daughter visited the flat on the day of the incident when she could not contact her grandparents.
When she could not enter, she alerted her father, who arrived soon after. They entered the flat after he broke a padlock securing the front gate and found the elderly couple in the bathroom.
Station Inspector Ariff told the court that Mr Ashikin touched one of them, believed to be Mr Omar, before he collapsed. The girl immediately called her mother, who alerted the authorities.
Responding to queries from The Straits Times, HDB said all flats built since 1985 have been installed with the RCCB.
It also said home owners of flats built before 1985 may have installed the RCCB as part of their own renovation.
This is especially so for flats which have been sold or resold since 1985, when renovation and electrical rewiring works are carried out.
It spokesman added: "As with all fittings and fixtures, RCCBs can be subject to fair wear and tear over time. Hence, as part of their regular home maintenance, flat owners should also test their RCCB regularly to ensure that it is in good working condition.
"Residents who are unsure what an RCCB is or where it is located can contact (an) HDB branch (office) for advice. We will explain to them what (it) looks like and where it is usually located."
HDB said that before testing an RCCB, it is important to switch off all sensitive equipment such as computers.
To test, press the "test" button to check if the RCCB switches off automatically and all power supply is cut off.
If the RCCB is in working condition, it should be reset after testing.
If the RCCB does not switch off automatically and cut off all power supply, it may be defective.
In such cases, a licensed electrical worker should be engaged to repair or replace the RCCB.
Four family members were in court on Friday but they declined to comment when ST approached them.