Trial of the effectiveness of thermostatic mixing valves



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Childhood injury in the UK

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The trial of the effectiveness of thermostatic mixing valves to reduce bath water scalds was a collaboration between the University of Nottingham, University of Wales Swansea, and Child Accident Prevention Trust (CAPT).  The project was led by researchers at Nottingham University's Division of Primary Care and Nottingham Primary Care Research Partnership.

Why are bath water scalds important?

Approximately 2000 children attend accident and emergency departments and 500 are admitted to hospital in the UK each year following a bath water scald. Most (86%) admissions occur in children aged under 5 years and two thirds involve a prolonged inpatient stay.1 The long term effects can include disability, disfigurement or psychological harm and repeated skin grafts as the child grows. Socially disadvantaged children are at greatest risk, with hospital admission rates three times higher in children living in the most as compared to the least deprived wards.2 There has been no discernible downward trend in attendances1 or admissions for bath water scalds over recent years.3

Water at 600C can result in a second-degree burn after 3 seconds and a third-degree burn after 5 seconds.1 The Child Accident Prevention Trust recommends that the water coming out of the bath's hot tap should be no hotter than 460C.4 However, boiler and immersion thermostats are frequently set at 600C or above.5-7 Attempts to reduce scalds by encouraging families to test their hot water temperature and to reduce thermostat settings have been largely unsuccessful. 8-11

Thermostatic mixer valves (TMV2s) have the potential to reduce bath water scalds. They are fitted across the hot and cold water supply pipes to the bath and restrict hot bath tap temperatures to 460C or below, but do not reduce the temperature of water stored in the hot water tank or produced by the boiler. The Housing Corporation’s Scheme Development Standards recommend their installation,12 but we do not know how effective they will be in day to day use by families or how acceptable families will find them.

Purpose of the research

This research assessed the effectiveness of TMV2s in reducing bath hot tap water temperature in the homes of families with young children living in rented social housing and assessed acceptability and adverse and potential adverse effects of fitting TMV2s.

Where did the research take place?

One or more local authorities, housing associations or similar organisations.

Who took part?

120 families with pre-school children living in rented social housing.

What was the intervention?

The intervention involved fitting a TMV2 valve to the hot and cold bath water supply by a qualified plumber. The cost of the valves and their fitting was borne by the housing provider. Families with children aged under 5, who agreed to participate were chosen at random to have:

  1. installation of TMV2 valve (60 families in intervention group)
  2. installation of TMV2 valve after follow up measurements have been made (60 families in control group)

How did we know if TMV2s are effective?

We measured bath hot tap water temperature before and three and twelve months after fitting of TMV2 valves in the intervention and control groups. Twelve months after fitting the valves we also measured 

  • valve failures, repairs and replacements

  • unofficial adjusting of valve temperatures by families

  • acceptability of valves to families

  • adverse effects such as scalds

  • potential adverse effects such as “topping up” the bath with hot water from other sources, reduced supervision of children during bathing or reduced checking of bath water temperature prior to putting a child into the bath.

Other sources of information about TMVs - the website of the Thermostatic Mixing Valve Manufacturers Association

There is a factsheet on TMVs in the FAQs and Factsheets area of the Child Accident Prevention Trust's website

Papers associated with the study

Kendrick D, Stewart J, Coupland C, Hayes M, Hopkins N, McCabe D, Murphy R, O'Donnell G, Phillips C, Radford D, Ryan J, Smith S, Groom L, Towner E. Randomised controlled trial of thermostatic mixer valves in reducing bath hot tap water temperature in families with young children in social housing: A protocol. Trials, 9: 14. March 19, 2008.  (Link)

Phillips CJ, Humphreys I, Kendrick D, Stewart J, Hayes M, Nish L, Stone D, Coupland C, Towner E.  Preventing bath water scalds: a cost-effectiveness analysis of introducing bath thermostatic mixer valves in social housing.  Inj Prev. 2011 Aug;17(4):238-43. doi: 10.1136/ip.2010.031393.

Kendrick D, Stewart J, Smith S, Coupland C, Hopkins N, Groom L, Towner E, Hayes M, Gibson D, Ryan J, O'Donnell G, Radford D, Phillips C, Murphy R.  Randomised controlled trial of thermostatic mixer valves in reducing bath hot tap water temperature in families with young children in social housing.  Arch Dis Child. 2011 Mar;96(3):232-9. doi: 10.1136/adc.2009.175059. 



1. Department of Trade and Industry Government. Consumer safety research: Burns and scalds accidents in the home. London: DTI, 1999.

2. Hippisley-Cox J, Groom L, Kendrick D, Coupland C, Webber E, Savelyich B. Cross sectional survey of socioeconomic variations in severity and mechanism of childhood injuries in Trent 1992-7. British Medical Journal 2002;324(7346):1132.

3. Eadie PA, Williams R, Dickson WA. Thirty-five years of paediatric scalds: are lessons being learned? British Journal of Plastic Surgery. 1995;48(2):103-5.

4. Child Accident Prevention Trust. Scarred for life.  Preventing bath water scalds in the home.  Discussion paper. Armagh: CAPT, 2002.

5. Huyer DW, Corkum SH. Reducing the incidence of tap-water scalds: Strategies for physicians. CMAJ: Canadian Medical Association Journal 1997;156(6):841-844.

6. Kemp A, Sibert J. Preventing scalds to children. BMJ 1995;311(7006):643-644.

7. Stephen FR, Murray JP. The prevention of hot tap water burns--a study of electric immersion heater safety.[comment]. Burns. 1991;17(5):417-22.

8. Katcher ML, Landry GL, Shapiro MM. Liquid-crystal thermometer use in pediatric office counseling about tap water burn prevention. Pediatrics. 1989;83(5):766-71.

9. Katcher ML. Prevention of tap water scald burns: evaluation of a multi-media injury control program. American Journal of Public Health. 1987;77(9):1195-7.

10. Webne S, Kaplan BJ, Shaw M. Pediatric burn prevention: an evaluation of the efficacy of a strategy to reduce tap water temperature in a population at risk for scalds. Journal of Developmental & Behavioral Pediatrics. 1989;10(4):187-91.

11. Waller AE, Clarke JA, Langley JD. An evaluation of a program to reduce home hot tap water temperatures. Australian Journal of Public Health 1993;17(2):116-123.

12. Housing Corporation (2003). Scheme Development Standards. London, Housing Corporation.