Up to 10 million people could be in danger from a plumbing fault that led to boiling water bursting from a tank and killing a baby, an inquest jury heard yesterday.
Ten-month-old Rhianna Hardie died when scalding water cascaded over her cot after the tank exploded in the attic of her council home in Taunton, Somerset.
Coroner Michael Rose said the problem with an outmoded thermostat which allowed hot water to flood the cold water tank could have national implications.
As he opened the case, Mr Rose said 3.5 million homes could be affected by the problem, and later said that equated to 10 million people "including some of the jury".
Matthew Hardie and his partner, Charlie Haworth, were spending their first night in the house in Wellington Road with their two children when the tragedy occurred.
Both Rhianna and her two-year-old sister, Emily, were put to bed in the room below the attic where the system was kept.
Mr Hardie said: "I awoke at around 2.30am although I didn't know then that that was the time. I heard a loud bashing bang and then heard Rhianna crying.
"I ran upstairs. Luckily I was dressed. Charlie followed me. There was a load of water pouring through the ceiling and thick steam. She was very hot - soaked.
"I had difficulty carrying her because of the heat. I only just managed to carry her downstairs and put her on our bed in the front room because she was so hot.
"I put her on the bed, then Charlie put her in a bowl of cold water downstairs. The ambulance came very quickly.
"It looked horrific. We knew immediately that she was badly injured."
Mr Hardie burned his arms as he tried to pull the baby to safety.
She was rushed to Musgrove Park Hospital for treatment but died three weeks later at Bristol Children's Hospital.
The incident happened on November 19, 2006 - the first night the whole family had slept in the house together.
Ms Haworth, the baby's mother, said that she had noticed hot water coming out of the cold taps that evening.
After they were woke by the explosion, she followed Mr Hardie into the room before plunging her daughter into a bucket of cold water.
Ms Haworth said: "Her skin was hanging from her toes and fingers like gloves and rolling back from her face. Her mouth was swollen and her tongue was swelling up."
The coroner told the hearing at Taunton Shire Hall: "There's no dispute that the death was a direct consequence of a problem that occurred when the thermostat in the immersion heater failed and boiling water overwhelmed the cold water tank which spilt and cascaded on to Rhianna, who was asleep in the room below with her sister.
"The house at Wellington Road was subject to modernisation in 1973. You'll hear about the type of installation that was used and how the incident occurred.
"This is important not only for poor Rhianna, but it could affect as many as 3.5 million houses in the UK. There has only been one other fatality involving an immersion heater, in Penwith, Penzance in 2002."
The inquest heard that many homes still had an old-style of thermostat with only one contact, which would simply allow the water to boil if it failed.
Robert Sutherland, plumbing supervisor for Taunton Deane, said the new versions have a second contact as a "cut out".
Since the incident his local authority had replaced most of the old thermostats "as a matter of course" although there was no obligation to do so.
Bernard Thorogood, representing the council at the inquest, said there was no legal obligation to carry out replacements for existing users.
The safer versions are only fitted as standard in brand-new installations, or when faulty thermostats are worked on.
The couple, both 22, now have a third child, Kadie, who is six-weeks-old.
John Williams, chief housing officer for Taunton Deane Borough Council, revealed that safety inspectors were not expected to examine the attics of houses "because they don't have ladders".
Mr Williams said: "There would not be an inspection of the attics because officers don't have ladders. They're not expected to look into the roof spaces.
"It's never been considered necessary to do something like that because we've never had an incident like this before."
He agreed with the parents' barrister, Dr Michael Powers QC, that the safety checks in place were essentially "reactive".
Mr Williams said: "Obviously we would not wish to let a property in an unsafe condition. We were not aware that we were letting a property in an unsafe condition."
The coroner pointed out that apart from the episode in Penwith, no thermostat had failed in 50 years before the Taunton disaster.
Mr Thorogood explained that British Standards safety checks were not required on thermostats in any case.
The coroner said: "The law may change after today, but there was no breach of statute or standards here."
Building supervisor Richard Eastman said that the type of thermostat in the couple's house was the old design that would carry on heating up once it had failed.
Modern models automatically cut out. There was no requirement on councils to fit the new makes on a "retrospective" basis, he said.
Avon and Somerset Police, the Health and Safety Executive and Taunton Deane Borough Council launched investigations following the accident.
The jury is expected to retire on Wednesday morning.