What Temperature Should Hot Water Be? | LEGIONELLA Explained

The last video about Legionella you will ever need. Adam explains the ins and outs of how to set your hot water for your personal circumstances!

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[megapangolin]

Excellent, helpful and very, very important video. I have learnt so much today in this one video. This should be on a government information programme and circulated to all councils for onward passage to everyone. There is health, safety, cost reduction and environmental guidance in here, and all done in a very listener-friendly style and presentation. Well done and thank you.

[johnmit]

It's also worth adding that in the UK the incoming water main (assuming it comes from a regulated supplier) will almost certainly have been treated with small amounts of chlorine to prevent bacterial growth in the supply network. So if you live in a house with modern plumbing (i.e. no redundant dead legs all over the place), and have a combi boiler or unvented cylinder with reasonable daily water turnover, then you are unlikely to have much (if any) legionella bacteria in your system to start with. If you however have a a vented cylinder with a header tank in the loft that has a lid that doesn't fit and old branches of pipework all over the place full that have been capped off and are full of stagnant water, then you might want to bump the temperature up as an extra risk mitigation. Or if you're vulnerable, worried and can afford it, consider getting rid of the header tank.

Commercial properties are more likely to have header tanks on both hot and cold supplies, and (from memory, but don't quote me), those are frequently identified to be the source of the contamination.

[brianpearson-wv]

My wife caught legionnaires 5 years ago. Spent 6 weeks on a ventilator and just pulled through thanks to brilliant NHS care. Still suffers after effects now. Believed contracted in rented village Spain as we were probably first users of season. Public health England took full details for notifiable disease but no feedback from Spain at all. My advice - if renting abroad water heating will be via storage cylinder so purge thoroughly at start of holiday. The 50% cases from abroad happen because we don’t do this 😢

[chrisfairbrother]

By dropping the tank temperature do you not also increase the percentage turn over as you’ll draw more hot water from the tank and mix less cold water. So the increased risk from dropping the temperature is countered by the increased turnover.

[andywaring]

I have yet to come across a single case of Legionaires disease from an unvented domestic hot water cylinder. Your reasoning is spot on and brilliantly presented with lots of info and clear explanation.

[alanclarke]

Thanks for refreshingly clear look at legionella risk. One push-back I've had on same evidence you raised for very low home risk is that
a)one cause of pneumonia is legionella, and pneumonia is not uncommon, especially in elderly
b)home hw is not tested for legionella, so
c)many cases of pneumonia could be home aquired legionella - but no one knows

[sietseroeda]

Thanks a lot. Exactly the information I was looking for.

[barneystevenson]

I went seeking information about the balance between boiler efficiency and risk of legionella infection. This answered all my questions and I am now running my condensing boiler at 45°C.

[nickwinn]

Solid advice. Storage vessel and pipework materials can also affect the risk of higher levels of legionella. Copper is toxic to the bacteria and as it tends to want to grow on a surface rather than in the body of the water, having copper pipes and hot water cylinders can reduce the growth rate of the bacteria.

[olivierboennec]

Adam, yodu nailed it again. I get into red hot arguments with my PH colleagues about resi hot water and they won't accept that 99% of home system already operate at 45 to 55 C. Great to meet you at the H&V awards and well deserved recompense.

[stever]

Another great video, thanks for helping us to reduce our energy bills.

When I moved into my house, I had an old Thorn boiler with copper cylinder and the only control was from a room stat and the boiler stat. The domestic water temperature was usually determined by the boiler output temperature and the boiler had a low output, so it was hard to keep the house warm. Accordingly the domestic water temperature was not particularly high, it was hot, but not uncomfortably, probably 40C.
That was the position for 30 years, with no adverse effects on our household of 5.
A new system boiler was then installed, with an S plan and a boost in room temperatures was noticed, a nice warm house and really, really hot water. Due to a fault on the boiler, I've had the boiler and hot water tank replaced. The new boiler temp was set at 80C and the cylinder stat at 60C. This caused the water at the tap to be scalding, but at least the house was very warm! I reduced the boiler output to 70C to reduce the domestic hot water temp, but it was still over 63C at the taps. Reducing the cylinder stat to 55C did not really result in a lower temperatures at the tap. It appears the hot water cylinder is heating from the top down, so the top of the tank is at the boiler temperature less any pipe losses and it warms down to the thermostat. I assume that when the water at the thermostat hits 55C it switches the boiler off and there is cycling on the thermostat. I have now reduced the boiler output to 60C to try and cut costs and importantly reduce the domestic hot water temperature. The water at the taps is now at about 57C, so some success, but I doubt that I'll survive the winter months without restoring the boiler to 70C, particularly during the really cold weather. Thankfully your video has given me more confidence to turn the cylinder stat down a little more. Thank you.

[kevingirdler]

Great video, I'm having these conversations daily with customers at the minute!

[davetaylor]

In Oz our domestic hot water comes set at 60C. Then there are compulsory tempering valves that come set at about 42C. The hot water cylinders can only be turned down to 50C min approximately. Our big thing in rural areas is tank water storage. Tens of thousands of litres of water just sitting there with minimal to no turnover as we have no mains water. These tanks can be plastic, tin or concrete and the temperature depends on the weather. In Summer we can have a shower straight from the cold tap. You don't need to add any hot water. Never tested to see what these tanks temperature range is but there are an awful lot of people on this system and never heard of any cases of Legionnaires disease. I have always associated it with commercial buildings as you say. Hospitals were always announcing cases. Perhaps that is the point. People get it but it is not diagnosed. You get crook in a Hospital and some test will tell them it is Legionnaires. The rest of us just think we have the Wog. Aussie slang for flu like symptoms.

[rrlabastida]

Finally what I wanted to check. We are happy at home with temperature set at 45C, but I was doing a manual legionella cycling twice weekly. I'll do eat once in a while now.

[tomm]

Absolute legend. I’ve been searching for these answers for a while as we have a water tank with an s plan system, so was concerned using low flow temps on the CH would cause the water tank to become an infested death trap. Very intelligent analysis and pragmatic especially the risk assessment

I already have my Heat Pump Boiler set at 45 degrees with anti legionella turned off. It's reassuring to see all this information that support my choice. Thanks for the really detailed information.

[davidrunnalls]

This is a very interesting video. As an marine engineer I have experience with potable water, there are a lot of other organisms living in water, so even with treated water you need to be careful about temperature in your hot water cylinder. I noticed after turning down the boiler and the electric thermostat that the hot water had an odour, as I have solar and battery storage I have turned off the gas boiler and use electricity only. I have found that the best temperature is 60c as this stops the smell. The amount of difference in consumption of electricity between 50 and 60 is negligible, I believe this due to us only having showers and have noticed that by having higher hot water we have the temperature on the shower much lower therefore using less hot water.

[geraldelwood]

Seems to be a very sensible approach of balancing the risks; accepting nothing is totally risk free.

[HorizonimagingCoUkPhotography]

Wow what an information packed video! 🤯 So helpful and clearly explained! Thanks so much! 🙏🏻😎