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By Stephen Walsh MSc, CEng., MCIBSE, FCIPHE, CMIOSH, MAE, Founding Member EWI and Accredited Expert Witness. Forensic Chartered Engineer and Expert Witness, Chartered Occupational Safety and Health Practitioner.

This is a Non-Medical article reflecting the Scalding experiences from my Plumbing, Public Health (Building Services) Engineering and Occupational Safety and Health investigations. Scalding is damage to the skin caused by wet heat. Excessive scalding to the victim’s body surface area can be FATAL. During the 1980 period when I became a Forensic Engineer / Expert Witness after 20 years of Plumbing and Public Health (Building Services) Engineering experiences in the UK and overseas there was no statutory or standards requiring control of hot water to sanitary appliances.

There were recommendations handed down from Plumber to Apprentice and continuum together with NHS requirements for their properties.. Initially when a victim had been scalded the Medical Expert would give the degree of tissue depth destroyed without having knowledge of the water temperature. In Litigation cases there was always a dispute as to the water temperature the victim had received. Then, as now, the only trusted data available to the Forensic Engineer being Dr.JP Bull of the Industrial Injuries and Burns Unit Medical Research Council “Temperature and Duration of Exposure Sufficient to Cause Burns in Thin Areas of Skin”. This information displayed in graph form with Time against Temperature in Degrees Celsius (°C) with the graph showing the “Partial Thickness Burns” and “Full Thickness Burns”.

Using this graph together from the information given within the Medical Expert’s Report it was possible to establish the range of temperature and duration of the victim’s contact. This information would be used to investigate the plumbing associated with the scalding incident with the view of finding the cause of the excessive hot water. The majority of my investigations were undertaken without the knowledge of the Medical Expert’s findings leaving me to assess the hospital notes of treatment and solicitor’s letter of instructions with or without photographs of the victim’s injuries.

With my personal interest in facilities for the disabled I wrote the first issue of the Institute of Plumbing (now the Chartered Institute of Plumbing and Heating Engineers) “Designing for the Disabled” within the Plumbing Engineering Services Design Guide which was published in 1988 and I set the temperatures for Wash Basins, Bidets and Baths at 38°C and lower for the user’s medical condition with the supply water being controlled by a thermostatic device. In 1998 with the death of 10 month old Rhianna Hardie, when a plasticised cold water cistern within a roof void collapsed onto this child sleeping in the bedroom below, I voiced my opinion for mandatory control to the Health and Safety Executive. They replied they would prioritise working to support the voluntary schemes for plumbers run by the Institute of Plumbing. Unfortunately volunteer schemes have no statutory control. In March 2006 there was a private members’ Bill tabled in Parliament Mary Creagh, MP for Wakefield, to stop Scalding Injuries and calling for all homes to be compulsory fitted with Anti-scald taps and controls on baths and showers setting the bath tap temperature maximum of 48°C. More than 600 people suffer from severe scalding injuries with a possible 75% being children. Scalding according to the NHS for healthy people without having a sensitive to heat medical condition can commence at approximately 40°/42°C. The causes of scalding from hot water have occurred during my investigations from Electric Showers, Combination boilers both condensing and non-condensing, gravity vented and unvented hot water systems.

A gravity hot and cold water system is one with an atmospheric cold water cistern installed at a higher level than the hot water cylinder. The cistern supplies cold water (cold feed) to near the bottom of the cylinder and hot water supplied from the top cylinder to the points of demand. The cylinder has a “Vent” pipe from the hot water supply pipe at near the top of the cylinder to allow the cold water to expand when heated inside the cylinder and to balance the atmospheric pressure in the water system when water supplied from the cylinder. The cylinder can have a primary heating source of a boiler. This primary water could be the same as the radiator heating system. This water does not mix with the domestic water used by the user of the domestic hot water. The cylinder could also have a standby/summer heating source provided by an electric immersion heater. The cylinder should also be provided with a thermostat to control the domestic internal water temperature. That was the easy principles now for the details which if not correctly installed can cause serious personal injury and a fatality.

1. The primary heating source to the cylinder heat exchanger has a flow and return pipe. The flow pipe from a boiler might have a thermostatically controlled maximum temperature of 82°C. The primary heat exchanger traditionally positioned towards the middle of the inside of the cylinder. The top of the cylinder containing the domestic hot water might reach the same temperature as the primary flow water should the cylinder thermostat be installed too close its base, equally the thermostat temperature might have been set too high. This thermostat should be connected to a solenoid control valve on the primary flow to stop the supply when the domestic hot water pre-set temperature reached.

2. The cylinder thermostat should not be set at a temperature higher than 65°C and not lower than 55°C. The BS 6700:1997 recommends not higher than 65°C and the Water Regulations Advisory Scheme (WRAS) Water Regulations Guide guidance states hot water be stored at a temperature of not less than 60°C. On larger vertical and horizontal Calorifier stratification can occur. This is when the hot and cold water volumes inside the vessel do not mix resulting in hot water to the top and cooler water at the bottom. There are plumbing engineering solutions to resolve this situation. The situation can occur with the cylinder thermostat in the cooler water zone and the top of the vessel has excessively hot water. The distributed water temperature should not be less than 55°C. The water temperature of 50°C should be supplied at the point of demand within 30 seconds after opening the tap full. The distribution temperature in excess of 50°C shall control microbial growth such as Legionella bacteria and unfortunately it shall also cause scalding.

3. An unvented hot water cylinder has its control valves set below 100°C. This system having its cold water supply provided directly from the water mains or similar high pressure source.

4. The supply pipe at the top of the cylinder must have a 90 degree bend immediately after the pipe connects to it. This bend is required to stop internal circulation within the vertical pipe which is extending the vertical capacity of the cylinder and the highest temperature the user of the system might come into contact after 30 seconds when fully opening the tap. This bend has an historical emergence (“Old” plumber’s technique handed down to apprentice), which has been found by present day investigations to be very important for energy conservation.

5. Another important issue is the height of the vent pipe top bend level above the cold water cistern. With the correct height as the water in the cylinder becomes heated it expands and the expanded water volume rises up the vent pipe. When the vertical pipe has been installed with insufficient height and/or reduced internal pipe diameter the expanded water flows from the open end of the vent pipe into the cold water cistern. This flowing motion has now created a circulation of hot water entering the cold water cistern. To replace this hot water, cold water flows from the cistern into the cylinder. This situation can continue until the cold water cistern contains very hot water for which it was not designed and the vertical walls and/or base collapse spilling the hot water contents into the roof space and the bedrooms below. However, not all cisterns collapse as might be made of metal or other temperature resistant material. In some situations the cisterns do not reach failure temperature. There is a plumbing engineering formulae for calculating the correct vent pipe height. Also should there be a circulation situation and the water not used from the cistern or cylinder the water expands and discharges hot water through the cistern’s warning pipe (overflow pipe). The domestic warning pipe normally manufactured of a plasticised material which can also collapse spilling hot water into the roof construction and the living spaces below. The final failure concerning the cistern being the float valve (ball valve). The plastic float fails due to the high temperature which results in continuous supply of mains water into the cistern for which the warning pipe cannot accumulate resulting in the water over spilling the cistern into the roof construction and the living areas below.

6. When the vent bend has not been installed correctly and the electric immersion heater’s own thermostat fails in the on position, the immersion heater continues heating the water with 3 kilowatt of energy which can result in the domestic water reaching boiling temperature. In this case steam will vent out of the open pipe installed at the correct height. However, the incorrect installed vent pipe shall result in boiling water flowing into cistern and causing circulation as previously explained.

I have investigated too many cases of collapsed cold water cisterns and warning pipes which have resulted in serious medical conditions and fatality. With the vent pipe bend being too low the cold water supplied to the tap or shower is hot and again I have investigated many scalding causes where the user had operated the cold supply only to be covered with hot water. Thermostatically controlled showers might have stopped this type of scalding incident. There have been incidents where people have turned the taps of the bath on and hot water was supplied from both. The users failed to check the water temperature before entering the bath resulting in serious scalding especially when one young mother put her young baby in the water before carrying out the “old grandmother’s test” of putting her elbow in the water. Yes the old tests are still the best. Another user had her feet amputated due to killing the tissue. Another where a disabled person in a nursing home was lowered in a hot bath and they died due to the degree of scalding and shock. A mother connected the two ends of a plastic hose to the taps and showered her child resulting in serious scalding requiring plastic scalp and facial medical surgery. The Building Regulations 2000 Approved Document “G3” Bathrooms, 2010 Edition, paragraphs 3.65 and 3.66 now states the water supply to a bath should be limited to 48C by using in-line blenders or similar approved device.

Another “old” plumbing tradition in England and Wales was to install the cold water and drinking water on the right hand tap of the appliance and the hot on the left except for the bath where the cold is always on the side close to where the user stands. This has been now written into the Building Regulations 2000 Approved Document “G5” Bathrooms, 2010 Edition, paragraph 5.5, “Where hot and cold taps provided on a sanitary fitting, the hot tap should be on the left.” Where the hot tap had been provided on a bath close to the standing edge I have investigated too many cases where young children have been allowed to play in the bathroom and it has resulted with them being scalded after turning the hot tap on. I can investigate the water temperature and plumbing system but the Court has to decide on whether there was negligence. I have also investigated cases where plumbers have undertaken work on systems without isolating the water supply which resulted in personal injuries due to being covered in hot water. There have been cases I have investigated where the personal injuries could not have resulted from the installed plumbing. Unfortunately for unknown reasons to me persons have in the past been prepared to submit themselves to personal injury and create an allegation for personal injury claims. It is possible to investigate such claims and provide plumbing technical evidence to the Court to substantiate a defence.

As an Expert I have a duty to the Court and to support the Court. I am a Chartered Engineer and Chartered Health and Safety Practitioner. I am an Independent Consulting Engineer since 1984. I have a wide experience of domestic plumbing, building services and maintenance issues relating to personal injury scalding accidents .

I have gained MSc Occupational Safety and Health specialising in the plumbing personal injury and industrial services accidents. I am a member of the Chartered Institution of Building Services Engineers, Fellow Institution of Public Health Engineers, Fellow of the Chartered Institute of Plumbing and Heating Engineers, Member of the Worshipful Company of Plumbers, Chartered Member Institute of Occupational Safety and Health, also Gas Safe registered in compliance Gas Safety (Installation and Use) Regulation 1998 reg.3 for domestic installations together with being a practicing Member of the Academy of Experts and a Founding Member and practicing Member of the Expert Witness Institute.

Below: View of an older type “Combined” Cold Water Cistern and Hot Water Cylinder” showing the Open vent and hot and cold water supplies.

I entered the profession as an indentured student apprentice Plumbing, Gas and Public Health (Building Services) Engineer during August 1964 and qualified as an Engineer in 1969. I continued my academic training and “hands-on” work development to complete my professional qualification when I was awarded my Chartered Engineer status in 1983. I became an Expert Witness during 1984. I have completed the Academy of Experts and Expert Witness Institute courses for Expert Witness. During 2005 I gained the Cardiff University Accredited Expert Witness Certificate by their examination. During 2000 as part of my on-going professional development I gained MSc. in Occupational Safety and Health. I specialise in personal injury caused by plumbing systems related accident investigations in the home and work place and accidents occurring to disabled people.

Since 1984 I have been instructed as an expert witness and given oral evidence in Civil and Criminal Courts. I have given oral evidence as an Expert Witness at High Courts in UK for gross negligence cases and at the Royal Courts of Justice, Technology and Construction Court London, together with regional County Courts. My Expert Witness duties are completed in compliance with B.S.EN. ISO 9001: 2008 “Quality Management” and BS.EN.ISO 14001: 2004 “Environmental Management” and BS EN ISO 18001:2007 Health and Safety systems to ensure compliance with CrPR Part 33 or C.P.R. Part 35 to the Instructing party’s instructions.

Stephen Walsh S.A.WALSH Specialist Consulting Engineers and Expert Witness Ltd., 27 Passey Place, Eltham, London SE9 5ZH
Tel; 0844 850 1918 Mob; 07786070333 Fax; 0208 850 6869. Email; This email address is being protected from spambots. You need JavaScript enabled to view it.


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