G3 (1) of the Building Regulations (England and Wales) states that hot water must be provided ‘to any washbasin in, or adjacent to, a room containing a sanitary convenience.’1 Under the guidance it states that: ‘in the Secretary of State’s view the requirement will be met if: the installation conveys hot water to the sanitary appliances … without waste, misuse, or undue consumption of water.’2 G4 states that: ‘adequate hand washing facilities must be provided in rooms containing (or adjacent to rooms containing) sanitary conveniences.’ In the guidance to G4 it states that the hand washing facilities: ‘…should be sited, designed and installed so as not to be prejudicial to health.’

So my question is, given the above, why can’t we legally specify just cold taps to wash basins in a school? I think we can, albeit not in a straightforward way, but a current Building Control Officer and the CIPHE’s former chief technical officer both say I am wrong. My contention is that as it is G4 that ‘sets out the requirements for sanitary conveniences and hand washing facilities’ and there is nothing in the Regs about deferring to G3, if I meet G4 why do I have to meet G3 as well? Crucially there is no statement as to whether the Secretary of State considers that washing hands in cold water is prejudicial to health and I would argue that specifying hot water at public hand washing facilities actually causes waste and undue consumption of water.

Waste and undue consumption from hot water taps

In the UK we waste hot water in two main ways when washing our hands in (most) public toilets. We turn on the hot tap, wait for however long it takes for the hot water to arrive, and then quickly wash and rinse our hands before the water gets too hot. Or, more usually, we get fed up waiting and wash our hands in cold water from the hot tap leaving a plug of hot water in the pipe. To prevent this second scenario, the Water Regulations require that hot water is available at the tap after 30 seconds in new buildings. This is usually achieved by a secondary return on the hot water distribution pipework; it will save water but the electrical cost of pumping hot water continuously round the circuit and the resultant heat losses from the secondary loop are both high. Added to this is the fact that schools, offices, hotels etc. use hundreds of thousands of litres of hot water disinfecting against the Legionella bacterium every year. Surely this is undue consumption of water, not to mention unnecessary CO2emissions and increased costs.

Washing hands in warm water – is it necessary?

Whilst a temperature of 70 degrees C will kill most bacteria instantaneously it will scald human skin almost immediately and most hand washing occurs at 40 to 50 degrees C. Research has shown that, under test conditions, it makes no difference if hands are washed with warm water or cold water. One study in the US showed that people who washed their hands with soap for just five seconds did nothing to kill the germs on their hands, but people who washed their hands with soap for 30 seconds killed everything.3 In another study participants washed their hands in water ranging from 4 to 49 degrees C; the temperature of the water had little effect on how effectively hands were cleaned.4

It is soap and hand friction, not hot water that is key to preventing the spread of infection. Using soap to wash hands is more effective than using water alone because the surfactants in soap lift soil and microbes from skin, and people tend to scrub hands more thoroughly when using soap, which further removes germs. Warm water is slightly more effective at getting soap to lather than cold water, but at the same time it can also have an adverse effect on hygiene as warmer water can irritate the skin and affect the protective layer on the outside, which can cause it to be less resistant to bacteria. The World Health Organisation, in its official guidelines on hand washing, doesn’t specify a water temperature, but does recommend using soap and water and scrubbing vigorously for at least 20 seconds.

So why are we so convinced that we need to specify hot water to washbasins? A study by the Vanderbilt Institute for Energy and Environment found that 70% of respondents believe that using hot water is more effective than warm or cold water for ‘killing germs’, despite a lack of evidence backing that up.5 Other research has shown there is a “strong cognitive connection” between water temperature and hygiene in both the United States and Western Europe, compared to other countries, e.g. Japan, where hot water is associated more with comfort than with health.

Successful cold tap specification

I have heard anecdotal evidence of schools in the UK that have isolated the hot taps to washbasins once they realised the cost of the legionella disinfectant regime. In Germany, washbasins in PassivHaus schools are supplied with cold water only. And I found an inspiring example of a district council in the US that turned off the hot water heaters in their five health clinics (saving US$2,500 a year) after their literature search validated that hot water is not required for proper hand washing or hygiene.6 As Part G is unlikely to be revised very soon what we need in the UK is for just one client to agree, one architect to specify and one building control department to pass a cold tap only installation – and then shout about it when they are successful. After that we would be up and running. So, who wants to be first?

Published in Green Building Magazine, Summer 2014


  1. The Scottish Building Standards 6 (Energy) 2010 do not specifically state a requirement for a hot tap at every washbasin but do state the requirement for a hot water service system to be energy efficient.
  2. This is a new requirement from 2010 updates to Part G. The requirement was stated in BS 6465 Part 3 2006 and the Water Regulations 1999 before then.
  3. From a study at Northwestern University, Chicagohttp://www.pediatricsafety.net/2011/04/hand-washing-101-kill-germs-don%E2%80%99t-spread-them/
  4. A 2005 study documented in the Journal of Occupational and Environmental Medicine,http://www.nytimes.com/2009/10/13/health/13real.html?_r=1&
  5. http://news.nationalgeographic.com/news/energy/2013/12/131213-washing-hands-hot-water-wastes-energy-health/
  6. Escambia County Health Department (ECHD) in Pensacola, Florida

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Washing Hands in Cold Water