What Temperature Should Hot Water Be? | LEGIONELLA Explained

[@chrisfairbrother4077]

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.

[@HeatGeek]

Yes

[@bimiuk4051]

Sorry you lost me here! Are you saying with 45c in cylinder tank mean that u will use a lot of hot water ? And reduce bacteria growth?

[@Timberjagi]

@@bimiuk4051 you need less hot water to mix to a certain temperature with a higher temperature.

[@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.

[@HeatGeek]

Yes, as per the video use the graph for pipework too

[@davetaylor4741]

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.

[@alanclarke4965]

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

[@HeatGeek]

B) we looked for cases of legiona aors desies not cases of legionella bacteria. We found lots of cases of legionella bacteria in homes, infactbis was EVERYWHERE! What we were looking for was cases of legionairs desies that were ateibuted to a domestic source and homes are tested when someone contracts it as well as work places etc to prevent an outbreak. A and C.. sure where is why we hugely over estimated that half of the 216 cases were from home sources even though they're less likely to have dead legs, unused showers, humidifiers etc etc

[@nickwinn7812]

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.

[@brianpearson-w1v]

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 😢

[@charlie6actual113]

As a legionnaire i have survived much higher temps just saying

[@jacko101]

Finally someone challenging the old wives tale about cranking up the cylinder temp to kill legionella. I was thinking exactly the same when you said how many people actually get legionella from lower water temps. You confirmed my suspicion, I imagine years ago it was some H&S department putting out this theory and now everyone just repeats it without questing if it's correct. Well done thanks for the research! 👍 I did find your hand actions a bit distracting after a while, just like the sign language people on the news 😆. But seriously, thanks for the video.

[@ricos1497]

For a channel that is so obsessed with data and scientific examination, I'm really surprised they haven't done an experiment to see the effects of gaffer taping his hands to the table for the duration of the video. Would make great telly.

[@johnbull5394]

@@ricos1497 Anyone of Italian background wouldn't then be able to understand him if we tied his hands up :)

[@geraldelwood9660]

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

[@andywaring12]

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.

[@johnbull5394]

Neither have I. But then I don't work in the medical profession. May I ask what your background is and whether you have come across cases from vented hot water cylinders, if not unvented cylinders? Sounds like you have some interesting data to share!

[@glightsolutions]

On the heat pump we service, we usually turn legionella off and leave hot water set to constant on (not constant running obvs) and set DHW temps to 40 to 50 degrees depending on the heat pump, cylinder, customer etc.

[@tomm7886]

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

[@barneystevenson1]

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.

[@HeatGeek]

I. Love. This

[@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.

[@bimiuk4051]

Is 45c still safe? Also does it mean the boiler would now work more effecient as it's low temp and work on condensing mode?

[@stever7915]

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.

[@cerealkiller4248]

You can fit a TMV ( Thermostatic Mixing Valve ) at hot water outlets to reduce hot water temps at the taps. You take a hot and a cold supply to the valve which then blends the two together to attain a pre-determined outlet temperature. This temperature is usually 43 degrees for taps, and 41 degrees for showers.

[@lucwillems5211]

since 2016 i have a hybrid solar/electric warm water boiler. since 2017 i´m controlling the electric heating using temperature sensor located in the middle of a 300 liter boiler with small siemens PLC. during less sunny season i keep the temperature up to 50C and then run a legionella cycle of 60C during off hour in the night so each morning the temperature will be maximum. 7..8 months of the year this system is heated mostly using sun , only during winter is mostly electrical. changing this has given more than 30% reduction, in electrical cost 😀

[@normanboyes4983]

Thank you for doing this video. It accords with my research too. However there seems to be a real vacuum of data when it comes to domestic properties and legionnaires disease and I wondered if Public Health perceive it as such a low risk they do not set up the necessary data capture mechanisms for dwellings.

[@HeatGeek]

It seems like the risk is speaking out means you will be accountable when or if there's an issue

[@davidrunnalls3039]

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.

[@pumpkinhead456]

The lawyers must have spent a while pouring over this one!

[@HeatGeek]

Not really, it shows you how to avoid Legionaires desiease.. unless we would be worried about people be too safe???

[@markatchison9974]

Interestingly "Legionella" doesn't exist as a word. It appears to be a combination of Legionnaires disease & Salmonella disease. At least in the bookish sense. However; each disease is quite different. Both are bacterial infections, though Legionnaires is a respiratory disease & Salmonella is a digestive disease. One is airborne & the other is foodborne. Also; Legionnaires disease is far more common in commercial water (hotels etc) because they use storage tanks rather than heating water according to demand (a domestic combi' boiler). If you visit a hotel in a hot country, always run your shower for a minute & leave the bathroom without breathing. This is because the water in the pipes & shower head is often held stagnant at around 28c.

[@megapangolin1093]

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.

[@selfbuilder1342]

A neighbour linked his hot water tank (set to 52 degrees heated by heat pump) to his dishwasher as it could take up to 60 degree water. Cheaper to run and higher water turnover.

[@typhoon2827]

52 degrees heated by heat pump? What HP is that?

[@selfbuilder1342]

@@typhoon2827 I beleive his is a Daikin Altherma 3. Most modern A2W heat pumps can go to 55c or higher

[@typhoon2827]

@@selfbuilder1342 haha. Yes, good luck with the bill at SCOP of 3.5 at 55C flow rates. What an ASHP can do and what an ASHP can do realistically for most people's finances are totally different. There are very few running at 55C flow rates. Daikin good manufacturer though. So your mate's dishwasher might be using less electric to heat the water, but you can't get something for nothing, no matter what he tells you 😂

[@jorkirasalas2726]

So what happens with stratification, when the water in the tank at the level of the thermostat is 55-60C, so the stat has turned off the HW heating, but lower down the tank it’s 30C?

[@HorizonimagingCoUkPhotography]

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

[@MarkGovier]

Ours has been set to 45C for decades. Never understood why cylinder stats went above 50.

[@Group51]

Ah. That’s a SunAmp benefit I need then. I might not escape the red zone on your chart with a cylinder!

[@nico101gaming]

I never tell customers to go lower than 55degs. Water Safe approved plumbers are told they must always recommend to set the stat to 60degs. I do however tell mine to set it no lower than 55degs with the premise that 5-10 degrees differential from a cylinder stat to the top of the cylinder

[@tommieronen7424]

Excellent video! Wonder how UV light would help to safely decrease temperatures.

[@Kristopher342]

A house full of teenagers should have no problems 😂😂

[@jamesheyes]

Late comment, apologies. If we ignore the legionella considerations for a minute… if a tank is heated to a lower temperature, the user will run down the contents of the tank quicker to achieve the same temperature from the shower/tap. This also means that the boiler has to heat MORE cold water to reach the desired tank temperature. Does this mean the savings are less significant?

[@alexweej]

If I understand your question correctly, the volume/mass of water needed for usage is indeed more, but the temperature you're trying to heat it to is lower. Crucially, the energy _loss_ (heat radiating out from the tank) is proportional to the temperature difference between the environment and the tank (mitigated, but not completely, by good insulation on the tank). So the hotter your tank, the more you're losing in terms of kWh (or £). Especially in the summer months in small flats this extra heat is painful, on top of the money wasted.

[@sipkebijlsma]

This video deserves at least 10000000 views !

[@normanpouch]

Been setting cylinder stats for 40 years to 45C. Makes the solar do more work and saves energy. Everyone one wins and no scalding. This clip maybe a sales pitch for ASHP also.🤣

[@eugenebarnes-f6s]

For those larger cylinders with slow turnover you can always fit a de-strat pump to flatten out the temp. variation between top an bottom of the cylinder. a one hour run per day will probably be sufficient.

[@chloehelliwell]

Big topic now people are trying to save on bills by turning off the constant setting on your boiler.

[@johncantor4056]

Excellent Adam. Surely there has been an elephant in the room here. Question is this... what temperature does the bottom few millimetres of water in the cylinder reach. e.g bulk of cylinder may reach 65 weekly, but very bottom only 40? A de-strat circulation, and keep it at 50 might be much better. If held at 50 all night,(longer 'soak') it will slowly conduct to bottom. Surely, monthly sterilisation OK, but done properly.

[@johnbull5394]

I see your point and agree 40° at base is quite likely, but there is legionella in the water supply (I think?) and it breeds from there. If so, then there will ALWAYS be a certain level of legionella in the cylinder, so not sure how much of an advantage there would be in getting the entire cylinder sterile. If the cylinder is constantly heated, 50°C makes sense if the bulk of the cylinder is actually getting to 50 as you would be drawing water from the top of the cylinder which would, in theory, have been in the cylinder long enough for the bacteria levels to die down. I suppose if you're heating to 65 and then using the water immediately, then some of the water will have been at an 'unhygienic' temperature for longer, but the fact that it has now been heated to a high temperature should mean the levels of legionella would start to die off much faster?

[@johncantor4056]

@@johnbull5394 I think the amount of legionella in incoming water is tiny... nobody worries about legionella with a cold shower. I am no expert, but have always believed that conditions where slow build (up to big numbers) can happen is the area of concern. Many controllers allow 1-month period, backing this thought. i.e. I feel it's those cold bottom areas where legionella could slowly build up over weeks. Are some strategies thinking that you accept legionella growth living at the very bottom, then kill it off before it gets to the top?? I would rather focus on the areas where growth might happen

[@justinjoanknecht3475]

Looking for some advice here. Am trying to minimise my energy bills with my new Daikin Altherma ASHP and Tank. It's a 210 liter tank and, with only 2 of us in the house, we will have either 2 or 3 showers a day plus use general DHW for washing hands, occasionally a sink of hot-water for non-dishwasher products. I'd estimate our daily usage of DHW to be 120 - 150 liters a day, so approx 60-70% of the tank. We also (as we are EV users) have much cheaper electricity from 2330 to 0530 in the morning (7.5p vs 27.94p /kWh, so nearly a quarter of the price) so the thinking is to put all DHW heating in that time frame. I've slowly brought the DHW setpoint from the installer settings of 60c down to 45c, heating from 0400-0530 on schedule only and this has been fine, this temperature of hot water comfortably lasts us all day, with it maybe once getting ever so slightly not hot enough after a particularly late night tennis match meant a shower at 10pm for me. Whilst I know that, though form a COP standpoint, 4am is probably not the most efficient time of night (as air temperature outside is probably at it's coldest), it actually seems to complete the heatup back to 45c in about 40-50mins (although I do concede it is May at time of writing and I suspect will take longer in winter!), my thinking here is that with my morning shower happening ~8am, it will have had less time to lose heat from the tank than if I did it at 2330-0100) - interested in anyones thoughts/comments on this logic? My main query though, is regarding ALC [disinfection] - I feel totally comfortable with reducing the ALC to 55c as my plan is to do this from 2330hrs once a week; whilst only 90% would die in 20mins, the rest would die in 5-6 hours which would be fine, as we will be asleep whilst that happens. Thoughts/comments from anyone on this logic? HOWEVER, according to the installer, the ASHP won't reach 60 or 55c without use of the booster heater which I'm loathe to use. Plus, having it on even on standby is incredibly noisy and of course it does just have a COP of 1.0 at best - yuck! I've tried turning it off [enjoying the silence instead of this godawful hum and gurgling all the time) and setting disinfect to just 55c and the tank reaches that temperature but the system still reports AH-00 disinfect error, which makes no sense to me. Can anyone help here? As it stands, I am thinking of either manually remembering to turn the booster heater system on once a week on "disinfect night" and suffering the hum all night or maybe installing a timer on that switch? Or do you think I'm totally fine to just let the ASHP get to 55c once a week on the ALC schedule itself and ignoring the AH-00 "error"? thanks for any and all help

[@kevingirdler3698]

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

[@mrcagas1158]

A very amazing video. A few questions please:- Is there legionella in all water regardless how old ,new,rain,hot or cold and it's just waiting for the right temperature or none movement. And once killed at 60° is there a time scale for it to reappear being open to atmosphere. Or if water was sealed from atmosphere once killed at 60° would legionella never reappear until open to atmosphere again

[@alcurtis93]

I have a big 150L water tank and there's only me and I barely use any hot water as wash hands in cold water and have a dishwasher and have very quick showers maybe 3x per week. It's quite frustrating paying to keep a tank hot all the time and needing to keep it at a high temp to avoid legionella due to low turnover but there we go. Can't see a way around it in a rental for the moment

[@effervescence5664]

Great info, domestic wise it makes no sense to be heating hot water over 60c. Yes the relative boiling point is higher in pressurised yet all the temperatures on the legionella course only talked about sea level legionella (open vent/gravity systems) rather than how it grows in pressurised. This is due to pressurised systems normally being chlorinated and although at a higher pressure increases boiling point slightly it doesn't increase the bacteria's resilience. The irony is doing the course basically tells you to heat it to 65c regardless. Although the temperatures on this video are correct should be taken into account for the care homes hot water regulations as it's a good rule set to follow. In where assisted bathing is 47c and unassisted is limited to 43c. Generally all new build homes are limited to an average of 46c via TMV at the outlets so there's not much point having the stored water hotter than that unless there's considerable heat loss before it gets to the TMV valves. Sadly as a commercial entity it doesn't matter what type of property we work in it has to be set at 65c because we get pulled up on it during legionella audits. So we just don't write down the information we provide the customer verbally for efficiency sake in domestic settings. Another case of one set of regulations not keeping up with others and new technology.

[@DanielOlivierArgyle]

I turned mine down recently so the temp comes out perfect for the kids baths. If we need to wash things up that can't go in the dishwasher, we just boil a bit of water. Painful to think how much money I've wasted in the past by not tuning it properly.

[@jwfukkink1608]

Currently I am installing an electric boiler, which will only be heated with excess solar power. The boiler will feed my current (natural gas-fired) heater so I will always have hot water even on cloudy days. Thanks very much for all your information on choosing the right boiler temperature etc. regarding the prevention of legionella! Crazy question: What if I would fill my electric boiler with demineralised water and run an electric pump to circulate the hot water through a plated heat exchanger in a closed circuit? And then run fresh, cold tap water through the other side of the heat exchanger? No tap water would be stored at all, so zero risk on legionella (and no legionella run needed). Optimisations: run the circulation pump only when hot water is demanded (flow detector); and add glycol to the boiler water to increase the heat buffer capacity

[@ebebop]

I’ve converted my combi to run a 300l unvented tank. The boiler has no option to high fire when heating the tank I had planned to use the immersion once a week to boost to 60c so I could maintain optimal heating flow and return. I’ve just set my Evo home to 50 (May go less) and I’ll boost once a month possibly. I have 4 kids 5 and under so high water use.

[@HeatGeek]

Evohome comes preset atb50 because they're aware 60 can be wasteful

[@ebebop]

@@HeatGeek What are your thoughts on the EVO home? I have it for every radiator and find the individual room control to be excellent. just a shame my 4 year worcester Cdi (not fitted by me) doesn't support opentherm out of the box.

[@HeatGeek]

@@ebebop room accuracy is amazing. Not the most efficient. Don't like battery replacement but think this kind of tech is yet to be fully harnessed. Tech/ai will harness more than people can

[@ebebop]

@@HeatGeek I get over two years per change on most of them, the lounge was just under two years, other rooms are looking like 3 year plus.

[@givemethejob3293]

Get rid of hot water cylinders, fit heat batteries like Sunamp, I do not work for Sunamp.

[@MrAshman3000]

Any saving we make on storing at 45c seems to be lost when the ALC does it's thing each week (ASHP) vaillant heats the water to 75c I'm thinking to turn the ALC off now.

[@johnc4323]

What time of day is your ALC set for? Make sure its early afternoon and not 4am, overnight is the coldest source air to the ASHP, vs a little after midday could be 5-10 degrees higher source temperature and higher COP

[@MrAshman3000]

@@johnc4323 It was originally set at 11am but I changed it to 2pm as the sun has come round then and warmed the air in the back garden 👍 Starting to notice it use more elec now it's getting a bit cooler

[@v_0]

This channel is gold. Shame most owners don't give a crap about 'the plumber's job'.

[@michaeldepodesta001]

Really helpful. Thank you for giving clear advice is this area which can induce anxiety in many older people. M

[@imranmajid1978]

Thank you for this extremely informative video; but please, please, please can you make a short video about possible planned power outages and what average home owners can do, will a small UPS/solar generator keep things running for a few hours at a time, how much power would a heat pump consume in around the same time?

[@colinnich]

There won't be any planned power outages - that's just scaremongering to try and stop people using too much energy now the price has been capped. And surely your house will stay warm enough without heating for 2 hours? If not, your heat loss is way too high to have a heat pump.

[@alanhodgson7857]

No "small UPS" will power a heat pump for any length of time, because it can't supply the startup power requirement.

[@alisoncarney1745]

hi i watch your video's on you tube but i am not a installler etc but intrested all about storage lowloss headers and efficiency etc but there is one question i have not had a video on this is i have a good effecent boiler but i have not found a electrical backup to power my 222f and extra pump and motorsed valves if we have power cuts or interupt supplys can i run it ie is it pure wave ups or invertor and will i damage my 5 year warranty as this year there might be power cuts and i can havd a ups with 33ah battery charged by mains then to a ups or invertor taking out there smaller 7ah battery as ups server unit are all over the place but no batterys can you do a video on what you would need ups or invertor ups mine ups 1.5kw but will i damage the boiler or warranty and i dont want to do that as this is best boiler i have ever had and gas usage etc is great but i dont want to be cold this year if cuts ps iam 67 BUT LEGIONNAIRES NEEDS TO BE ADDRESSED HOT WATER AND SHOWER HEADS LUCKLY MY VIESMANN TANK HAS THIS FACILITY THANKS ALISON

[@nickwinn7812]

UPS's always have pure sinewave inverters, to my knowledge and they will not harm your system. Make sure the inverter has enough power handling capability to handle the start-up of pumps etc and that the battery will give a good long run time at the average power consumption of your system (you can always add a bigger battery external to the UPS for this purpose, but be aware that it will also take longer to charge a bigger battery).

[@peterjones6322]

No need to bump up the temperature if you have a dishwasher because they take in cold water only, and heat it internally.

[@paullenton2076]

Another school day even after over 30 years in the trade 😊

[@radishpea6615]

If a tap is 10 yards from the hot water tank and used once every 3 months, do I need at least "55" degrees at the tank or the tap?

[@Game0verFool]

My Vaillant Ecotec Pro 28 has DHW set to 40° but if I check the boiler while hot water is running I see it reaching up to 63° 🤔

[@roberthuntley1090]

Good video, with lots of common sense. I was thinking the other day, if legionella was a major risk in domestic systems we would all be worried about the cold water tanks in the attic (of traditional build houses). The water from the tank is usually directly connected to the cold inlet of the bath mixer tap (which often includes a shower hose) and over the summer months the water must spend many days between 20 C and 45 C, given the ambient loft temperature (which peaked at 45 C in my case) will stay in that range. The tank is insulated to prevent winter freezing, but that just slows down the rate of heat ingress. Its also topped up with chlorinated mains water, but that flow stops when the family goes away on holiday for a week or more. However, as far as I'm aware there is no evidence of an uptick in infection rates afterwards.

[@HeatGeek]

This is why we meantion vold water stores in the video and advise to insulate them. The insulation advice isn't to stop them freezing, that's even less likely, it's to stop them getting too warm in summer.

[@MrFlyby34]

As a Dutch guy I often wondered why in the first place you would install a watertank in the loft? After some research I understood it's because if water mains fails. However this is an very old fashion method and not used as far as I know on the continent. A system like that is quite bad in terms of water quality and very prone to legionella....

[@roberthuntley1090]

@@MrFlyby34 Thanks for coming back. Another advantage of the tank is that its kinder to the water supply system by reducing peak flow rate demanded. You can run a bath full of water quickly, without knowing or caring that the tank will take tens of minutes to refill. Means smaller pipes and pumps in the supply system, so hopefully lower bills. Just to be clear, cold taps where you might ingest the water (drinking, cooking, teeth cleaning etc.) were supplied directly from the water mains so this mitigated the contamination risk. The cold water tank only supplied baths and showers. The system was pretty universal in the UK until combi boilers swept it way about 20 years ago.

[@rainbowevil]

Really good and interesting video! One question though: how do you measure or calculate or estimate your daily turnover percentage? You put a lot of focus on that but didn’t explain how you can figure yours out. I have a combi boiler, so does that mean it’s very high almost regardless of how much I use, since there’s no storage beyond what is in the pipes?

[@ajayshah95]

I was wondering this too.

[@joels7605]

Temperature stratification is insane, and much worse than you think. My tank will reach steady-state equilibrium with a 55C setpoint, but the bottom remains in the 23-25C range. It will not naturally equalize. I had to install a small mixing pump from hot outlet to cold inlet. My tank is quite large and made for solar installations. I had to install a 1100 watt heating element at about the 1/3 height mark. So there's about 400mm of water below the heating element. I can measure the temperature of the hot water tank at any point along its height by testing the outlets, of which there are many. The temperature stratification is wild. If left for a week with absolutely no water usage the bottom of that tank will stabilize between 23-25C, even if the rest of the tank is holding steady at 55C. The temperature drops off very quickly below the heating element. I would have bet that convection or conduction would mix the tank somewhat, but nope. It blew my mind.

[@chrislaf2011]

Conclusions all sound reasonable. Just one thing re the stats for risk of domestic incidents of Legionella. Is it possible, given the believed prevalence of 60C storage, that the lack of incidents is a kind of confirmation bias? In other words, the low number of incidents is due to this policy. Nonetheless, your arguments to lower temp to level appropriate to throughput and risk level all make sense.

[@HeatGeek]

Most systems are set to 50 not 60. Above 60 is against building regs

[@matthewwakeham2206]

Not everyone gets legionnaire's disease. You might just get joint aches and cold or flu like symptoms.

[@HeatGeek]

Shouldn't get anything if the video is followed though

[@johnbull5394]

Hi Adam, May I start by saying that I welcome the fact that we are having this level of discussion? To give the personal background, my cylinder stat is set to 60°C, but I actually ignored the stat dial (I find they are generally inaccurate) and measured the water temperature at the cylinder outlet when the thermostat decided it was satisfied, so that's 60°C at the top of cylinder. As the cylinder lagging has been improved by a Heath Robinson extra lagging arrangement, it is only necessary to heat water 3 times a week. This suggests that we are only using 30-40% of the cylinder's capacity on a daily basis. However, the shower is electric so the main way legionella could enter anyone's lungs from the DHW cylinder can be ruled out. I cannot really argue with your approach, and I think people in domestic properties would be generally wise to take your advice. Although I would note that the low number of cases in domestic properties is likely to be partially down to the fact that most people do store their water at a high temperature, because that's how most plumbers set up the cylinders. You mention that pipework and showerheads may contain legionella. I'd love to know if that's really a problem on pipework that is not subject to stagnation. Probably the distributing pipe to my bath is full of it as it's not even used weekly, but the fact is that once you start to run a bath, it's immediately filled with 60°C water means that the contaminated water is likely to represent less than 2% of the content of the bath, so the average bacteria content of the filled bath is still likely to be quite low. Same applies to my electric shower, which, once it has dumped the first pint of water, is running on water that has only been stored for a few seconds. Interesting as this technical discussion is, however, my understanding is that the so-called Water Regulations 1999 insist that stored water be stored at no less than 60°C. Technically, that's the DETR guidance note G18.2 of the blue book, so it's not technically law, but, if the DETR is recommending it, it kind of seems like official "best practice" even if I don't really agree with it. What I'm seeing in Part G is 3.64 which states not a maximum _storage_ temperature of 60°, but a maximum _supply temperature to the distribution system_ of 60°C if the water is normally stored above 80°C so if you can actually direct me to the part of ADG that contradicts what the DETR has said, that would be great.

[@JeremyCobb]

Hi, great video. We are about to move into a new home that has been standing for ages. It looks like it has a combi boiler. What should we do before using the water to be safe and before we can get an engineer in to service it

[@HeatGeek]

Just run the taps for 5 mins. Any build up will wash out almost instantly

[@aurimasgriskevicius]

What water heating scenario would you advise from your professional practice? - there is an electrical 2kW 200L water tank in the basement, which is used only on Saturdays for ~3 hours and only used a half of tank or less. - heat losses of the tank at T=65°C are 1.40 kWh/24h, but the basement temperature is ~16°C, so I think heat losses are bigger. - there is a thermostatic valve - there is no risk of burns. - there is a timer for a tank to work on sunny hours because there is a solar plant on the roof. Which scenario would make more sense in terms of energy efficiency, legionella and limescale prevention (as I know, above 60°C heating element starts limescaling): 1. heating for ~2h daily to reach 55°C. Daily water would be in the range of 45-55°C. 2. heating only on Saturdays for ~6h to reach 70°C. Weekly water would be in the range of 20-70°C. 3. heating only on Saturdays for ~4h to reach 55°C. Weekly water would be in the range of 20-55°C. 1 scenario is better for legionella and limescale prevention, but not energy efficient, because it is not only necessary to heat the consumed amount of water, but also the heat loss of 7 days. 2 scenario is better for energy efficiency and legionella prevention, but over time, the heating element will become limescale and will no longer be energy efficient. 3 scenario is the best for energy efficiency and limescale prevention, more water passes through the tank than at 70°C, but the risk of legionella is big, because for 7 days the water will be below 40°C and will drop to 20°C. And only for 1h will be 55°C. Maybe the solution is to discover the number of hours at 55°C to destroy the bacteria that have multiplied in 7 days? Thanks for the information! Amazing clips. Very useful information.

[@bimiuk4051]

Interesting! I got a 170L invented cylinder tank (round 27yrs old) And a new Ideal Vogue Max. Wanted to get OpenTherm and PDHW but not having much luck at moment. All this cos I wanted to have a much lower temp flow for the CH but but but .... Since it's possible to actually lower the cylinder stat boiler to round 50c - does it also means the CH will automatically work in a condensing mode ??? Or does it have to be at 45,c to achieve best performance? We are 2 adults and one little child. I am not sure how much hot water we use from tank. No idea how to calculate the turnover in tank.

[@jeanforthewin]

I like the way the mitsubishi QUHZ units and thermal stores do it - your "hot water" storage is actually a sealed system and your actual hot water is done instantaneously via a plate heat exchanger (like a combi boiler). As water is heated straight from cold incoming to hot outgoing you can store at whatever temp you want to allow you to get the outlet temp you want. So you could store at 45 to get 40 out with the worries about legionella. Would like to see this implemented with other heat pumps as well

[@HeatGeek]

Lower scop though. Every time you heat 1 medium to heat another you have to increase source temp and lower effy

[@jeanforthewin]

@@HeatGeek but increased scop with lower storage temp and no legionella cycle

[@HeatGeek]

@@jeanforthewin it won't be a lower storage temperature and ALC aren't needed in most cases

[@jeanforthewin]

@@HeatGeek if you're coming from the commercial world where you have to comply with L8 it's way better than storing at 60.

[@johnnyfandango1625]

It's what I have been saying for years. The amount of energy wasted getting water too hot to then be blended down is huge nationally. I have been running our heat pump cylinder at 45 degrees for 6 years now and I have never run an anti-legionella cycle.

[@ricos1497]

Me too. I've had legionella less than three times in the last five years. Completely ridiculous guidelines from the nanny state.

[@johnnyfandango1625]

@@ricos1497 Less than 3 times? I've had covid more times than legionaries disease in the last 6 years. Or maybe it wasn't Covid!!

[@alcurtis93]

i would run it occasionally. You are asking for trouble eventually

[@nickbea3443]

@@ricos1497 Nice try.

[@Ribeirasacra]

Safety in Domestic buildings is ok for housing. However what about vacation rentals? Buildings are empty at times no regulations of cleaning or how low temps they have to maintain. I have read that owners of these properties are looking to save money in heating. If that is the case will cases of Legionella rise. Is it time to revise regulations to include vacation rentals?

[@AlfisGarage]

Very well presented. One question - most modern homes have circulating pumps to have hot water right at the tap - I guess that would help with the "stagnant water" issue? In theory, there should be no stagnant water in the cylinder even if not all of the water is used.

[@Muppetkeeper]

Soooo, as most homes in the UK either have a combi boiler, or a hot water tank set to 60°C, we shouldn’t expect to see any legionnaires disease from homes should we. I’d be interested to see what happens if we all turn our tanks down to 50°C.

[@HeatGeek]

Most tanks are set to 55. Not 60.

[@Muppetkeeper]

Ahhh, ok, mine was set to 60°C, until it was ripped out and replaced with a heat pump and new tank. Now at 48°C, with a legionella cycle every two weeks. I may see if I can turn that down to 55°C though.

[@MrDavegeo]

How do I find out how much hot water I'm using? We're a youngish family of four, but all told we probably take about 8 showers (pretty short with water off while we soap up) over a week and wash at the sink the rest of the time so I'm thinking that we'll be lucky to use much more than 100l of our 250l tank (40%) a day? Presumably there's no chance of me turning the temperature down below 65 on our unvented system boiler to allow for 53 degrees plus to cater for such a low turnover?

[@mushtaqshah9390]

Many thanks for the video. I have a system boiler. If the flow temperature set to 60 and I have cylinder stat temp on the cylinder to 50. Regardless of the flow temperature, the cylinder will stop when it reaches 50? Am i doing anything wrong by setting the flow temp higher ? I have just done this for the radiators to be at a higher temp. I have a vailent ecotec 635. Any advice would be welcome. Thank you.

[@Duncan-Bizkitts]

Great informative content as always. I looked at my water temperature on my Vaillant ecotec plus 837 and have adjusted down to 53 degrees, however I’ve found it overrides this setting and gets as high as 69 degrees according to readout. Any idea what the problem might be………

[@Bob_too]

If the Cylinder Stat is say set to 45 degree, what level would it be economical to run the Boiler HW at ? Note Boiler HW is currently set at 80 and has Domestic HW Priority, and CH is set to 60.

[@ReneMaurin]

Very informative - thank you. But I still have a dilemma. My situation is such we don't need overly how water most of the day. We need hot water in the morning and just luke warm water the rest of the day. I have set a DHW schedule so we heat up to 50 at 6 am and then let it drop to min 35 to boost it up a bit again in the evening (to 40). The water surely goes into the "danger zone" each day for some hours and as we have two elderly I don't want to risk anything. What would be the best safety / economy approach? A weekly anti leginenella cycle or raising the temperatures all together? I guess with present low temperatures setting we do turn around most of the tank. I am thankful for your take on such regime!

[@MrTrevorroe]

I have brought the same idea from Telford cylinders for years, KIWA and Wras stoped this cylinder due to first 1 litre of water doesn't get heated and may cause legionnaires, glad you have got round this with WRAS, good job 🎉😊

[@pedromonteiro6043]

My heat pump cylinder (Ariston Lydos 80 L) only does an anti-legionella cycle once a month and only if you activate it. Since everyday our water is kept at 53⁰C and 4 people take daily baths, after watching this video I will deactivate the anti-legionella cycle.

[@Pegasus4213]

Your commentary with its smart cutting-out breath pauses reduces comprehension time for older perhaps slower comprehending adults. Which is surely the point of making such videos. What do you gain by cutting our breath /comprehension pauses?

[@firmbutton6485]

I Like facts. So much hygiene overkill out there. Ie ads showing moms of young kids wiping surfaces with raw chicken breast!

[@rutger1963]

I have an Intergas xtreme 24, hot water temperature set to 45c, flue gas temperature is 30c, as soon as you not purchase hot water, the exchanger block temperature goes to 85c, so no legionella here, and a nice and economical boiler!,and pipes and shower head I'm not so afraid of, 2 x shower x 2 people, per day, there is more than enough flow,legionella has no chance to grow!

[@tomkirkland]

Central Heating Header tanks in the middle of the Summer, there’s your Legionella breading ground. 🤢 Gloves and masks are a must. Never heard of a case myself from a Domestic Cylinder.

[@nigelbamford7206]

Excellent evaluation of risks, especially important when energy savings are needed more than ever.

[@mosfet500]

Our hot water is tankless, the holding tubes are less than a gallon, also I have UVC to protect the system. This is why I like tankless systems, no legionella, no cryptosporidium, no standby losses and the water temp is 40.5 C (105F), so no mixing losses and very low line losses. I think tankless is better than tanked and even heat pumps, it's cheaper, simpler and longer lasting. A tankless will last indefinitely, even after 25 years if you have a tube or element go you can replace it.

[@vvv435]

Aren't there so few cases of Legionella because all domestic tanks in the UK at the moment are set to 60 degrees to prevent it? That only means that the current protection is actually working. Are we really suggesting for non-specialist people to asses their own risk of Legionella and would you anybody take responsibility for such advise if somebody dies or becomes crippled? The safety requirement to store water at 60 degrees is there for a reason.

[@supersai4198]

460 cases per year, so basically it's not even worth mentioning.

[@swisby3820]

Great summary of the BIG debate….. BUT most shower thermostatic mixing valves need the hot water at least 10C above the desired mixed temp for the cartridge to work correctly, so 50C is my own base temp and it allows less storage as the lower you go in storage temp, the more hot water you use

[@ctrayes]

Great vid as a side note some countries such as Australia required a legonella kill according to the plumbing code at or above 60 deg C at least once per week or 55 Deg C for atleast 6hr per day. On top of this scald protection is required to prevent tap water being above 50 deg C in alot of cases. Over the top if you ask me.

[@Donevigor]

I purchased a new build recently which has a condensing system boiler for heating and hot water and a storage cylinder in the hot press with immersion. I was looking for a way to drop the heating temperature to 45 while keeping the hot water in the cylinder 50-55c. Sadly the boiler doesn’t have separate temperature controls so I can only change both. Would having the immersion on the timer during the night work to ‘boost’ the temperature? I’m not sure what happens when the water in the coil is cooler than the water in the cylinder?

[@hannahjones7281]

Great video - i suppose the challenge as a designer is we don't always know our end user! However we should design for flexibility and optimisation because a lot of this is controls based it can be altered.

[@PaulCiot]

Hygienic water tank is the solution. Or upgrade your boiler to hygienic type. Also you can increase the time lifespam.

[@1over137]

I have a combi. I set it to 42*C as that gives me a nice full open hot tap shower. For everything else, there is bleach or bleach containing spray.

[@keirstitt8277]

Really informative. On the stagnant water risk. Often circulation pumps on long lines can result in water being less than 40C [especially if cylinder is at 45C] but continuously moving until it returns to cylinder. Is this a risk already addressed by the fact the water is circulating? Or do additional measures need to be considered?

[@TheFriskyBiker]

I’ve got a gas combi boiler that heats water on demand, how would I know what my water turnover is and how much of the capacity I’m using?

[@loracle540]

BUT All the water coming into a property from the public main is clorinated! If you have been away for a few weeks, as you pointed out water does not remain long when a house is occupied so, when you return run it hot or run it cold and there will be no legionella

[@scraser77]

Please stop click baiting it destroys your credibility

[@HeatGeek]

What part of this title is click batey?

[@davidkelly4841]

Interesting chat, have you considered that the data showing the risk to be minimal, is distorted because we keep our water at 60c? The other point is even if shower heads and pipe work have a high concentration of legionella, there is not much volume, so pretty low risk, vs a hot water tank full of the stuff?

[@HeatGeek]

We don't. People who have been through nvq level 3 are told not below 50 for legionella and not above 60 for scalding. 50 is the standard most controls come pre set to like honeywell evohome, viessmann controls vailant etc etc

[@davidkelly4841]

@@HeatGeek ok, thanks for replying, same statement but for 50c?

[@HeatGeek]

@@davidkelly4841 yes sure.. but not 100% of people do.. some don't.. and in decades we haven't had an issue...

[@davidkelly4841]

@@HeatGeek Thanks! and thanks for making the video

[@duncan1945]

Great video, told me exactly what i wanted to know. Thanks.

[@pauls826]

I can see what your saying about running a low temps if you’ve got family and your hammering your hot water it’s not going to get chance to breed if fresh water is going in every few hours

[@WillsB3]

Silly question, but how do you measure what your water turnover is from the cylinder?

[@HeatGeek]

Good point shower uses around 75L. Bath is 130 odd

[@Etacovda63]

Test your flow rates from your fittings and calculate. The hard part is knowing how much cold you’re mixing in

[@mickinmerton8053]

I run the hot tap in the bathroom basin with a cooking thermometer in the flow.

[@Etacovda63]

@@mickinmerton8053 thats a temperature, not a flow rate.

[@alanclarke4965]

How long can you go without reheating the cylinder? Hot water stratifies, so hot stays at top and cold comes in bottom - when you start to get cooler water out of the tap you've used all the hot water so leaving reheat off till then should indicate turnover - 12hrs: 200%, 24 hrs: 100%, 48hrs: 50% - of course also few deg cool down from cylinder loss (but that should be well insulated by 2022, surely)

[@SuperJonArne]

I have a hot water tank and a single temp control on the front of my boiler. If I set thermostat on the hot water tank to 45 what do you recommend as the minimum flow temp on the boiler to make sure it doesn’t take an age to top up the hot water?

[@HeatGeek]

50 to 55

[@SuperJonArne]

@@HeatGeek I tried turning down the flow temp on my boiler to 55 but it doesn’t seem to fire properly. Turned it back up to 70 for now to be safe

[@Outdoorshuntingshooting]

I knocked my combi boiler down to 40 deg cel recently. As used everyday the pipes should be clear of any buildup ever occurring.

[@Commsfarage]

My thermo only controls the heat pump for radiators have a log burner with boiler.

[@scottticketsplz]

If I drink cold water out the tap why am I worried about legionella?