'Flight Shame' - Legionella - water safety

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@Robert_Hodge

That’s fascinating, thank you. Are there exceptions to this tho’? Only the other day on the thread re air source heat pumps Paul Flimders wrote

“Turning the flow down to 55° (line 3) mitigates the performance at low air temps quite a bit but, while the system will produce some heat down to -10, it’s only kicking out half its rated output at that point though. Also 55° is a bit low for the hot water temp, so if you are using the heat pump for domestic hot water you need to make sure that there is an immersion heater and that the system is setup to do a pasteurisation cycle once a day - I’m a bit stuck as there is an immersion but not controlled by the system controller so I have the hot water set at 56° - just hot enough to kill legionella, with the flow a couple of degrees above that, not brilliant for efficiency but as low as I dare go.“

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Robert’s comments make some sense, however I believe the NF require storage at 60°

Don’t forget that, although there are bacteriological standards the water supply must meet they aren’t “zero bacteria” and water is often stored in the distribution network (eg in château d’eau).

Also, you actually want the water coming out of the hot tap to feel, well, hot (preferably not scalding though).

Finally I should add that in my own system I have the additional constraint that I’m not there 90% of the time so I have a 300l tank sitting at whatever the basement temperature is (typically 20° or a little higher in the summer down to about 10° in the winter), so I do want that up to a temperature which will be bactericidal when we arrive.

It doesn’t alter the basic fact that air source heat pumps are not a good match to traditional radiators or DHW systems.

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There are of course many different variations in domestic water installations here in France, especially with some older properties where the system has been altered over the years.
However, let us consider a few basic facts.

  1. The cold water delivered from the mains supply is safe to drink and it’s quality is checked on a daily basis by the water company.
  2. If the cold water remains in a pressurised and sealed pipe or tank that was clean at the time of installation, then it is difficult to see how bacteria can enter the system.
  3. Where the piping system consists entirely of approved grade plastic or copper pipe, it is virtually impossible for the water to become contaminated.
  4. Thermostatic mixer taps on baths and showers are fitted with with a safety stop set at 38 deg C.
  5. There is no way that anyone would wish to hold their hand under a running tap where the water emitted is at 50 deg C or above.

Therefore, in the case of a correctly designed and fitted direct feed system such as an electric ‘ballon’ type of hot water heater that is in permanent daily use, there is no problem with turning down the thermostat to a lower temperature.

Having said that, I do accept that there are folks whose water comes from a private well or ‘forage’ where the quality may be variable and is not subject to daily laboratory checks, and also folks who leave their system drained down for periods of time with taps left open where insects and microbes could enter the system. It’s these differences in standards of installation / use that gives rise to the advice to flush the system out if it has not been used for some time.

Where the water system is of the constantly pressurised direct mains feed type, and the system is in constant daily use, then there is no problem at all with turning down the thermostat because there is no need to kill germs that simply are not, and cannot, be there.

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44

Rather than drinking, I think it is the droplets containing bacteria - which can be inhaled - that give rise to the disease in us humans.

I’m fairly sure I read somewhere (ages ago) about some shower-heads possibly harbouring the bacteria, if they were left unused over a period.

For a while I got into the habit of tapping/banging/changing the angle of our large shower head - so that the water trapped therein actually drained out. Now that the shower is used regularly, I don’t bother - although, perhaps I should. :upside_down_face::thinking:

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In respect of Legionaire’s Disease that is indeed correct in over 90% of cases. It’s the reason why outbreaks of the disease are often associated with faulty air conditioning systems in buildings frequented by a large number of people.

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Yes, but it’s easy to get an aerosol - turning the tap on full will generate one quite nicely a lot of the time as the stream of water hits the bottom of the sink.

I’m not sure I’d turn the thermostat below 50° but low 50’s is probably a good compromise.

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Ah well, our boiler has a safety setting of 60c for Hot Water and specifically states that care must be taken when using hot water during the CH cycle - as the 60c will be over-ridden. :upside_down_face:

So we have fitted thermostatic mixer taps on the showers.

No mixers/thermostats on the baths or basins. Never had a problem so far (touch wood) as most folk seem to run both taps at more or less the same time.

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I don’t disagree at all with the domestic water being delivered being safe to drink. It is, but I don’t think that is the same as bacteria free. And there are things other than legionella that can cause problems if the population builds up.

There are also time when the faecal matter content in our water analysis has risen, still minuscule but I’d prefer it not to be there at all.

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Anyone who is interested - here’s an interesting “water” link

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Ah, legionella. Now, I’m an actual expert on this, not an armchair one, as I am trained and qualified to write legionella risk assessments and management plans. Bear with me, I might rattle on a bit here but hopefully will set your mind at risk and keep you safe.

Legionella is a bacteria which grows in biofilm in water. Biofilm being basically, sludge. You can drink water which is infested with legionella bacteria and it will not harm you. The problem comes when you breathe in droplets with the bacteria in as it then goes into your lungs and reproduces, effectively giving you bacterial pneumonia. You have an 80% chance of surviving this condition. Diabetics and smokers are at higher risk than others.

Legionella cannot survive above 55 degrees or below 10 degrees, so temperature is an important factor in control. The recommended temps for hot water is 60 degrees at point of delivery and under 20 degrees for cold water. It’s not just the water system and where it comes from that is important though, so is design. Biofilm congregates in what are called ‘dead legs’ i.e. pipes which have water that sits in them for a long time. You’d think a nice modern building like the Scottish Parliament would be free from issues, wouldn’t you, but it isn’t. In their infinite wisdom, they put in a load of washing machines, all on the same pipe run and connected to the main supply. They don’t get used a lot, so water builds up in the pipes and so does biofilm. The whole site is on permanent disinfection because they can’t get the levels down to acceptable.

How does this affect you? If you have a second home, or stay in self catering and you are unsure how long it has been since the water was used, open the windows and turn the cold tap on. Flush the system for 10 minutes (ouch, cost, I know…) to clean the pipes. With the shower, best to take off the shower hoses before you leave your property, and when you return, disinfect them for 20 minutes in a bucket of Milton. When you put them back on, (or if you can’t do the disinfect) tie a bag around the head (with a hole in it), open the windows, run the shower for 10 mins and leave the room when you do it.

If you do rent your property out and you keep your thermostat at 60 degrees, please do put stickers up. Vulnerable users such as folk with MS may simply not register the temperature and end up with burns. Care homes and hospitals are restricted to 43 degrees at point of use.

Bearing in mind that legionella thrives in biofilm and at 38 degrees, personally, I wouldn’t get in a hot tub to save my life. Dead skin, warm water, bubbles, air full of moisture. I also avoid the salad sprayers in supermarkets like the plague too.

In short, flush the taps, keep the water hot, don’t breathe in the vapour until you have flushed the system. Oh and don’t have a jacuzzi bath with friends :wink:

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51

Hi , My wife and i are moving to France this summer.
As it happens i am a Water industry approved plumber and am currently employed as a water hygiene engineer .If anyone out there would like an evaluation of risk and implementation of measures to prevent legionella or other nasties Please feel free to contact me :grin:

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Hi Darren

Why not join our conversation on Legionella etc - if you have something interesting to say.

Re coming to France - will you be retired here - or are you planning to get yourself French Accreditation ?

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Hi Stella, retire without retiring and without a pension,52 at the moment. Not sure about French accreditation…

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Ah… so what is the Plan ?

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Hello Helen

Thank you for explaining the risks and how we can help protect ourselves so clearly.
Good advice for those with second homes and gites but difficult to implement if one is renting a holiday home.
Luckily not too many jacuzzis or salad sprayers in my neck of the woods (!) it’s something that most of us would never think about.

As is usual on SF we have strayed away from the original topic but it all makes fascinating reading.

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Will get to the plan eventually,for now take some time out and enjoy our cottage in the country.
Dont want to be alarmist a chap died last year in England watering his garden!!
Golden rule :Try to empty the water from hose and or remove the spray head for the first 30 secnds or so…Everybody waters the garden…?

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57

Well that’s a reason to be pleased that for the last few years we’ve had a hosepipe ban!

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Is that all of France ?
We are moving to Brittany, The heavens may play a large part in watering the veg.

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Not here they don’t, we are in a situation crisis red area and it’s banned !

Make sure that your area doesn’t have water restrictions or bonfire restrictions as the fines can be hefty, the powers that be are quite rightly having a crackdown …

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What area are you