He went to take a shower but was found motionless minutes later.
Gregory Ng Kok Rui, 17, an Institute of Technical Education graduate, was taken to Changi General Hospital last August, where he was pronounced dead about 1½ hours later at 11.50pm.
The teenager, who was waiting for his National Service call-up, had been electrocuted.
Yesterday, a coroner's inquiry into his death found that he could have received the fatal electric shock when his left hand came into contact with an electrically energised metallic shower outlet hose that was attached to a water heater.
Investigation officer Staff Sergeant Hendry Johan told State Coroner Marvin Bay that the water heater had been installed by an unlicensed electrical worker.
Taxi driver Beh Kim Ek, who had been working as a freelance technician since 2000, had done electrical work in Gregory's family flat at Block 1, Hougang Avenue 3, about three months before the fatal incident.
They included replacing a socket outlet in the kitchen to which the water heater was connected.
An electrical appliance shop owner, Mr Peck Yew Hai, had recommended Mr Beh to Gregory's grandfather, Mr Anthony Ng.
Sometime in May last year, Mr Beh went to the flat to replace the socket outlet.
About a week later, Mr Ng bought a new water heater from Mr Peck's shop, Seng Ann Radio Electrical Company, and which Mr Beh installed.
Staff Sgt Hendry said that one night after the new heater was installed, Gregory was having a shower when a power trip in the flat caused a blackout for about two minutes.
Mr Ng reset the flat's circuit breaker.
"(After this) the water heater functioned well without any further incidents of power trips," Staff Sgt Hendry said.
But tragedy struck on Aug 29.
Five minutes after Gregory went to have a shower at around 10.15pm, his family heard him shouting.
His grandmother, aunt and brother rushed to the bathroom and saw smoke coming out from the socket outlet to which the heater was connected.
Staff Sgt Hendry said: "(Gregory's grandmother) immediately turned off the switch while protecting her hand with a (piece of) cloth. (His) aunt also noticed that the faceplate of the socket outlet was burned with visible black soot."
They forced open the bathroom door and found Gregory motionless on the floor. After calling for an ambulance, his aunt performed cardiopulmonary resuscitation on him until paramedics arrived at 10.40pm.
Mr Loh Mun Wah, an investigation officer from the Energy Market Authority (EMA) told the court yesterday that he found that parts of the neutral cable and the earth cable in the socket outlet had melted and fused together.
This indicated overheating that could have been caused by factors such as a loose connection.
As a result, when the water heater was being used, electric current flowed to its copper water drum which was connected to the shower hose that Gregory had touched. The court also heard that a power trip did not occur as the circuit breaker was found to be faulty.
Staff Sgt Hendry said: "When the current flowed from the metallic outlet hose into (Gregory) as he was showering, he was electrocuted as the (circuit breaker) was faulty and did not operate as intended to cause a power trip."
Mr Loh said that homeowners should test-trip their circuit breakers once a month to ensure that they are working properly.
Coroner Bay will give his findings on March 12.
This article was first published on February 28, 2015.
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