Hi Paul, this is a question for a water engineer, but just because the temperature in your garden office is 29.1 degrees C doesn't mean that the underground mains supply would be anything like that (even in the South East of England).

Have you asked South East Water what they would expect the mains supply temperature to be after a period of prolonged above average air temperatures and little rainfall?

Will depend on a number of variables inclusive of the material the pipework into a building is made of.

Hi Paul

Thanks for the added information.

Can't help with details of those who could supply such equipment but I wonder whether the investment could be justified except in situations with a particularly vulnerable population (such as the care homes you mention).

However even in such scenarios you could define the time when monthly checks should be carried out, so that you get a more representative idea of what the cold and hot water temperatures are for most of the day - legionella isn't going to suddenly breed exponentially when a hot tank has just been refilled with cold water and takes an hour to heat up to above 50 degrees C.

Also, I wonder whether businesses should be continuing to rely on raising cold water to elevated storage - that sounds like obsolete systems from days past when mains water supplies were less reliable (though I do realise that a village covered by SE Water is currently doing the news rounds!!)

The basic technology is different in the South East than up here in Glasgow - in the SE lots of abstraction from below ground whereas just about all Glasgow's water flows down from the hills - but the same overall principles apply - i.e. is the mains pressure sufficient to consistently get the water up to higher levels? - if, YES, then you should not need the high level tank storage.

But overall the question is probably one for a ("clean") water (as against "dirty water" - i.e. sewage etc*) engineer to answer.

*I have worked alongside many water engineers - most have tended to get specialised into either "clean" OR "dirty" - though perhaps less so in smaller engineering practices.

Thanks Peter and Chris for your comments.

This is one of those areas of compliance that has allowed a whole industry to grow around it.

my client has around  5 small estate agent shops that each have a toilet with hand basin and point of use heater and a small kitchen area for making drinke etc. with a sink and hot and cold taps.

a few years ago (before I was involved) they had legionella risk assessments and were told that despite not having showers or any aerosol making outlets, they needed to do monthly temperature testing. If you want to do this yourself, you can buy a kit for around £100, but for some reason, the legionella industry has got fixated on accurate thermometers. So you need to pay another £100 to get the thermometer checked in a lab. And recallibrate it every year or so. Personally, I think for low risk sites that this is ridiculous. 

Why would it matter if you were a degree or 2 out?  You are not constantly monitoring, just monthly temperature sampling, so very inaccurate for an overall picture. Maybe if you were right on the cusp - say 19.5 degrees, you could argue for greater accuracy, but a lot of the time, you cannot do much about slightly high summer temperatures anyway.

So, we also manage about 70 buildings for clients. Many are small residential blocks (4 -10 flats over 4-5 floors in London terraces). We need to check sentinal temperatures in these blocks because there is a genuine life risk as low water pressures mean some need communal storage tanks and all are going to have showers in the flats. We pay contractors to go around with their callibrated thermometers and take monthly temperatures.

I am aware that a lot of tech companies offer to fit thermometers to the hot and cold pipes in the sentinal flats and on the inlet/storage tank, with a transmitter, so you get 24/7 real time monitoring of the water temperatures.  This does away with the need to visit and gain access This is also much more useful, because whereas a hot tap might not be hot enough during a snapshot sample, the real-time monitoring will tell you if during the 24 hours, it achieved a high enough temperature for long enough to thermally disinfect the system. If the price was right, I could also use it in the offices.

But I don't know anyone who uses such a system and can advise on plus and minus points.

I was hoping someone would be using this type of kit.

Very interesting to read this topic, makes me wonder about my hot tub.  When filling from empty during summer months the temp. shows as 21C, where in winter it is much lower, about 16C.  I'm in Wirral.

When in the tub and using the jets I can see the "wet mist" appearing above the water surface.  I do use correct chemicals regularly and test the water but just wonder if I should be considering Legionella ?

I'm confident others have a Hot Tub and many holiday lets have them also.

Originally Posted by: firesafety101

Very interesting to read this topic, makes me wonder about my hot tub.  When filling from empty during summer months the temp. shows as 21C, where in winter it is much lower, about 16C.  I'm in Wirral.

When in the tub and using the jets I can see the "wet mist" appearing above the water surface.  I do use correct chemicals regularly and test the water but just wonder if I should be considering Legionella ?

I'm confident others have a Hot Tub and many holiday lets have them also.

There is a well known case (in the water industry at least) of a legionella outbreak at a hot tub supplier who had units running in the showroom but didn't do treatments etc as it no one was actually getting in and using them.

On hiliday a few weeks ago the park operators did a temp check every morning

I believe you're right about size of outbreak.

UK had its own though unfortunately; JTF in Stoke on Trent. Had to drop a few lines down my Google search to find a link that wasn't the Daily Fail ....

https://www.itv.com/news/central/2017-07-03/jtf-store-fined-1-million-for-legionnaires-outbreak-in-hot-tub-that-killed-three-people

MrAmerica might like to read the forum rules before placing a blatant advert - REPORTED

Thanks Roundtuit

Perhaps the next Space Invader on these Forums will be MAGA or even DonaldJTrump?