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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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  1.  
    Mine wasn't anywhere near that efficient at DHW temperatures, though the new ones are getting better. Still got transmission and tank standing losses on top of that though.

    Horses/courses though, sure that GE will be pleased with his and won't catch Legionella from it!
    • CommentAuthorMikel
    • CommentTimeDec 16th 2018
     
    Tony,

    You posed the question:

    "How many people have ever got ill from legionella in a domestic hot water system ?"

    I did a quick google and saw this from Health Protection Scotland

    https://www.whatdotheyknow.com/request/135812/response/335799/attach/3/FOI%20480737%20response.doc?cookie_passthrough=1

    This is the relevant section:

    "The second part of your request was for the following details:

    The number of cases where the infection was specifically determined to have been contracted from domestic hot water supplies in Scotland. (Specific information on the numbers resulting from *domestic* hot water supplies - not hot water supplies in hospitals, factories, hotels and so on.)

    For these cases, please indicate how many of them were confirmed by microbiological testing ie where testing showed that the organism found in the hot water system was indistinguishable from the infecting clinical strain.

    HPS Response

    For community acquired cases in 2009, 2010 and 2011, three have been linked epidemiologically to the case’s domestic water supply. In one case the evidence was highly indicative (same strain identified by culture in the case and the domestic water) and in the other two cases the evidence was indicative (strain cultured from the domestic water; tests from clinical samples indicative of this strain, but samples not taken from the case that were suitable for culture and therefore more complete strain typing was not possible).

    These three cases were in 2009. The environmental investigation for these three cases, carried out by local authority environmental health officers at the request of the NHS board,,found that the most likely source of exposure was a hot water tap within each of the cases homes. The presumed cause of the exposure was the build up of Legionella bacteria in the hot water system, in one case caused by recent plumbing work to the system.

    Cases are usually definitively linked to a particular source on the basis of microbiological, epidemiological and environmental evidence. With regard to the microbiological evidence, the same strain and type of Legionella bacteria are isolated from the patient and from water samples taken from the source. Legionella bacteria prefer warm and slow moving or stagnant water. The latter can occur in recently disturbed water systems – where repairs or replacements have been made. Environmental investigations focus on identifying if there is an increased risk of Legionella growth within a system, and may not result in samples being taken and tested. In short, not all cases of community acquired Legionnaires’ disease are accompanied by testing of water samples taken from the case’s home or suspected source in the community.

    For further information about legionellosis in Scotland in general, please see our webpage: http://www.hps.scot.nhs.uk/resp/legionella.aspx?subjectid=185,97"

    If you look into their reports in more detail, they state an incidence for legionella of 6-8 per 100,000 and that is a total for all causes not just domestic hot water.

    Considering there are over 2.4 million homes in Scotland, the incidence is quite low. However, we should be careful not to be complacent. As we move to renewable energy systems, it is likely that DHW will be stored at temperatures lower than 60C and instantaneous heating will be less prevalent.
    •  
      CommentAuthorDamonHD
    • CommentTimeDec 16th 2018
     
    IMHO the better solution as suggested above is not to store heat in the water that will come into contact with humans. Keep the DHW pipework short / low-volume and hold heat (where instant is not sensible) in a thermal store.

    That thermal store can be water or something like Sunamp's rather more compact and low-loss phase-change material.

    Rgds

    Damon
    •  
      CommentAuthordjh
    • CommentTimeDec 16th 2018
     
    Posted By: Mikelthe most likely source of exposure was a hot water tap within each of the cases homes

    Thanks for finding that response, Mikel. It's useful data. It's an interesting and worrying detail that the presumed infection source was a hot tap rather than a shower in each case. I must take care not to breathe whenever I use a hot tap!
    • CommentAuthorgyrogear
    • CommentTimeDec 16th 2018 edited
     
    Posted By: DamonHDThat thermal store can be water or something


    all the more so if said thermal store can be fitted with an immersion heater, controlled by a weekly timer and adjustable thermostat to guarantee the anti-legionella holding time/temperature...

    gg
    •  
      CommentAuthorDamonHD
    • CommentTimeDec 16th 2018
     
    If the thermal store is sealed, or not water, why waste heat 'pasteurising' it?

    Rgds

    Damon
    • CommentAuthortony
    • CommentTimeDec 16th 2018
     
    +1
    • CommentAuthortony
    • CommentTimeDec 17th 2018
     
    The hot water tap seems odd to me as Legionella is reportedly only dangerous as an aerosol and can be ingested without harmful effect.

    Something is not right here
  2.  
    Posted By: tonyThe hot water tap seems odd to me as Legionella is reportedly only dangerous as an aerosol and can be ingested without harmful effect.

    Something is not right here


    We have aerating taps and it is possible to see a very fine spray coming from the tap at high pressure.
    • CommentAuthorgyrogear
    • CommentTimeDec 17th 2018
     
    Posted By: DamonHDIf the thermal store is sealed, or not water,


    agreed, but if it is NOT (like mine...)...

    gg
    •  
      CommentAuthordjh
    • CommentTimeDec 17th 2018
     
    Posted By: PeterStarck
    Posted By: tonyThe hot water tap seems odd to me as Legionella is reportedly only dangerous as an aerosol and can be ingested without harmful effect.

    Something is not right here

    We have aerating taps and it is possible to see a very fine spray coming from the tap at high pressure.

    It would be even more odd if all the cases reported were from houses with aerating taps and especially if that fact were not noted. It would be very interesting to have detailed case information about those three cases, but I suspect it doesn't even exist.
    • CommentAuthorgoodevans
    • CommentTimeDec 17th 2018 edited
     
    Yes its not clear whether the 3 cases reported above in 2009 found a match in only one hot water tap per dwelling - or the strain was matched from a hot water tap but other taps /outlets were not tested or tested clear.

    It looks like for community infections the authorities only look for a source in large systems (workplace etc). I suspect the reason is that up till now a source is usually found in these locations and not in the domestic setting - or it is so difficult to find a source in the community they don't bother.

    So, as is often the case, - no testing to asses the risk for the millions of existing domestic installations, no testing to see if control measures reduce the (unknown) risk - but plenty of advice to 'do something' (of unknown efficacy) to reduce the (unknown) risk.
  3.  
    A friend of mine actually got Legionnaires. They never properly tracked it down, just that it was possibly from a roof mounted cooling tower in Chesham high street.

    He doesn't recommend it.
    •  
      CommentAuthorDamonHD
    • CommentTimeDec 17th 2018
     
    Chesham High Street?

    Seems harsh.

    Rgds

    Damon
    •  
      CommentAuthordjh
    • CommentTimeDec 17th 2018
     
    Posted By: goodevansIt looks like for community infections the authorities only look for a source in large systems (workplace etc). I suspect the reason is that up till now a source is usually found in these locations and not in the domestic setting - or it is so difficult to find a source in the community they don't bother.

    I think they look for sources in large systems when there is a group of infections, and similarly they test large systems because they can potentially infect large numbers of people. Domestic systems would usually infect very few people, and those very people probably carry resistance to any strain present in that system by repeated exposure so it's not cost effective or popular to require testing of all domestic systems.

    FWIW, my father had it, including a period in intensive care, and no it's not nice. He got it from a roof-mounted cooler in Spain.
    • CommentAuthortony
    • CommentTimeDec 18th 2018
     
    I have a comment from an expert and they would expect something like three random unexplained cases in that population over that time span.
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