SINGAPORE: People should check their water heaters regularly and make sure it is not using a three-pin plug, experts said.
This comes after an elderly couple and their son died in a flat in Jurong Lakeside in December 2020 after being electrocuted because the cables in the plug supplying power to their instant water heater fused together.
The flat’s heater was powered by a three-pin plug connected to an extension outlet, which was in turn connected to a power outlet in the kitchen, said an Energy Market Authority engineer who testified during a coroner's inquiry.
When the plug to the water heater was opened after the incident, the cables inside were “badly burnt” and the earth cable and neutral cable had fused together.
The engineer said that the cables fused because they were overloaded. The plug had a 13-amp fuse but the maximum current when the water heater was operating was more than 14 amps.
CNA spoke to experts about how you can ensure your water heater is safe.
- Water heaters should be connected to a switch for water heaters, not a three-pin plug
Electricians and engineers CNA spoke to said a three-pin plug cannot support loads higher than 13 amps, and currents for water heaters are larger than that.
Instead, water heaters should be connected with a switch meant for water heaters. These are usually ones with indicator lights when they are turned on.
Mr Benetton Chan, director of electrical and plumbing services company Sparkflow, said it is still common to see three-pin plugs used for water heaters in some homes.
Many homeowners have been using water heaters with this setup for more than 10 years with no incidents, he added.
“The plug itself supports up to 13 amps. The heater uses, let’s say 14 amps. That means the plug itself will have to work even harder to fulfil that 14 amps, but the limit for that plug is only 13 amps. It gets hot because it works even harder, and that’s why the wire burns,” he explained.
"The regulation has always been to use a heater switch."
If the water heater has already been installed wrongly, homeowners should call an electrician to change the wiring, he stressed.
“We will have to run a new set of wires from the main circuit breaker, all the way to the toilet,” said Mr Chan.
His team usually charges about S$100 to S$200 for this, depending on the distance, he added.
- Look out for other changes to the water heater that might indicate electrical damage
Connection points are the “most common places” that start to heat up when water heaters run into issues, said Mr Wang Gucheng, senior manager of the clean energy research centre at Temasek Polytechnic’s School of Engineering.
People who notice a burnt smell should call a professional electrician, experts said. If the switches start to turn black, this could be a “telltale sign” that the wires are burnt or about to start burning, said Mr Chan.
They should also contact an electrician if any part of the water heater or switch feels unexpectedly hot, said Mr Wang.
- Buy water heaters with the Safety Mark and a leakage detection protection function
Experts stressed that people should make sure that the water heater they buy should have the SG Safety Mark.
“Some water heaters have a leakage detection protection function. If you purchase that one, there is a test button that allows you to test that function. Test the protection function regularly,” said Mr Wang.
A normal water heater may last between eight and 12 years, he added. If the water heater becomes old, homeowners should get professional electricians to check on the condition of their appliances.
A typical water heater has a warranty of up to five years, said Mr Chan.
“As long as it crosses the warranty period, it’s better to check already. I think that’s the safest way,” he added.
- Installation of a water heater should be carried out by a licensed electrician
Mr Chan and his team have also encountered people who have tried to install their own water heaters, even though they do not have the appropriate electrical work licences.
“They think it’s not working, then they call us. They complain that it is the heater’s problem. In fact, it is their installation that is incorrect,” he said.
When hiring an electrician to install a water heater, homeowners can ask the worker to show them their licence card. The card should have their photograph, their name, identity card number and licence number, said Mr Wang.
These electricians have been trained to ensure that the wiring is done correctly and safely. They also have professional equipment that can detect any potential risks in the current wiring or connection, he added.
Mr Chan also advised homeowners to have a professional electrician check their water heaters “every once in a while”.
“There are a few things you have to check. First is if the wires are still intact or not, if there’s any sign of burnt wires. Also the switches – switches could burn as well, depending on how the previous installer tied the wires, or ... the quality of the wires,” he said.
“All these things will not happen suddenly. It will slowly build up, so (it's) better to get an engineer to check for you.”
It can be difficult for people without a proper electrician licence to check on the status of the water heater and the wiring, he noted.
“You don’t know what’s inside ... unless you open up everything,” said Mr Chan, adding that he has seen instances of correct wires being used in the visible parts near the switches, but the wrong wires used in the parts that are not exposed.
“There will be instances like that, so first thing ... is to get a proper electrician to do all the wiring.”
- Check your earth leakage circuit breaker or residual current circuit breaker in your distribution board box
Homeowners should also check regularly that their earth leakage circuit breakers or residual current circuit breakers are working properly, experts said.
In the Jurong Lakeside flat incident, the engineer who testified in court said that the household’s electrical circuit comprised two wiring systems: An older system installed in 1971, and a newer system installed when the flat underwent the Housing and Development Board’s (HDB) Main Upgrading Programme completed in 2003.
As part of the HDB upgrading, a residual current circuit breaker (RCCB) was installed for the newer wiring system. The RCCB would trip the system and cut off the current when an earth leakage was detected.
The water heater drew electricity from the older wiring system, which was not protected by the RCCB as there was no such requirement at the time the system was installed, he told the inquiry.
He said that if the RCCB had been installed in such a way that it protected the household’s entire circuitry, it would have detected the earth leakage during the incident, tripped and cut off the current.
Homeowners should ensure that there is an RCCB in their house’s distribution box. They can ask a licensed electrician to teach them how to test it regularly to make sure that it is working, said Mr Wang.
If the earth leakage circuit breaker or RCCB is working correctly, it will trip during the test, and all the electricity in the house will immediately shut off, said Mr Chan.
If the electricity does not shut off, something is wrong, and homeowners should call a professional electrician for help, he added.
- What to do if electrocution occurs at home
Beyond checking the water heater and its components, homeowners can wear slippers when they are showering to reduce the risk of getting electrocuted, said Mr Wang.
They should also stop using the water heater if they feel any tingling sensation when using it, he added.
“When you’re electrocuted, you don’t have the time to react,” stressed Mr Chan.
In the Jurong Lakeside case, one of the deceased was holding onto a metallic water hose and not wearing any shoes as he was taking a shower. This caused the man to be electrocuted, said the engineer at the coroner's inquiry. His wife died after she went into the bathroom to help her husband.
Water was still flowing from the shower head when their son arrived to check on them. Upon seeing his parents on the floor, he ran to them, and then collapsed and fell on his mother’s body.
If someone at home gets electrocuted, family members should immediately cut off the main power supply using the distribution box, said Mr Chan.
“Do not try to touch the person if he or she has been electrocuted,” said Mr Wang.