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Discuss Hot water temperature from Domestic immersion cylinder in the DIY Plumbing Forum area at PlumbersForums.net

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I have my immersion cylinder thermostat fitted to wall, at 90 deg to the inlet from the diverted valve, was told this was the best position.

I have a digital thermometer fitted at this point and it shows 43oC with an outlet temperature of 54oC, measured with an oven thermometer inserted against the copper pipe inside the insulation, with the hot water tap running slightly. Is it likely that the water is at 60oC ?

the cylinder temperature at the stat, is usually 47oC, so assume the outlet temperatures would be around 58oC, which I think could guarantee the water is at least 60oC, does that make sense ?

problem at the moment is the boiler, or more accurately the pump..( detailed in another post ) so the boiler spends an awful amount of time starting up and shutting down. Seems to be worse when hot water & heating on together.***.so heat hot water in the night between 3am and 7am, depending on how the boiler performs as to what temperature is achieved. Running the boiler at 72oC outlet to keep the inlet below 55oC , as its a condensing boiler. DT across the boiler only around 20oC
My other question is, if I don’t heat the Hot water continually, will this mean there is a risk of legionaries ? Or is it sufficient to heat it ups as I am doing over night ?

once the new pump is fitted, March / April, hopefully can leave hot water on constant..

thanks
 
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Heating up to 60 once a week is sufficient to prevent legionella. Without a photo your description is a bit confusing, cylinder thermostat should be attached to the cylinder.
 
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Heating up to 60 once a week is sufficient to prevent legionella. Without a photo your description is a bit confusing, cylinder thermostat should be attached to the cylinder.
Yes it’s attached to the cylinder wall....was just pointing out that it’s not directly opposite the inlet flow, as been told this can affect the stat.***.

gald to hear about legionaries, so HW in the night should be fine.***.

just need to ascertain from my figures available sensors that the HW is above 60oC
 
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Yes it’s attached to the cylinder wall....was just pointing out that it’s not directly opposite the inlet flow, as been told this can affect the stat.***.

gald to hear about legionaries, so HW in the night should be fine.***.

just need to ascertain from my figures available sensors that the HW is
 

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Thanks, just didn’t know that once a week at 60oC was enough, haven’t seen that anywhere else.***..
wonder if I can safely say I am at 60oC with my figures
To be fair the “committee” has produced HSC document L8 which recommends daily sterilisation to 60 WITH a destratification pump to make sure it’s all stirred up. This is very rare in a domestic setting and would use loads of energy. I suspect most tanks in the UK vary from room temperature at the base to 65 at the top.
 
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To be fair the “committee” has produced HSC document L8 which recommends daily sterilisation to 60 WITH a destratification pump to make sure it’s all stirred up. This is very rare in a domestic setting and would use loads of energy. I suspect most tanks in the UK vary from room temperature at the base to 65 at the top.
Thanks 👍👍👍
 
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Gbpeck stated heating HW to 60oC once a week is enough.***.but found this.***..not sure what to think now

Hot water should be stored at 60°C or higher at all times. Often homeowners reduce the temperature as they think it will reduce energy usage or turn off their hot water tank altogether when going away for some time. This can create favourable conditions (temperatures between 25° and 50°C) for Legionella bacteria to breed.



It is, therefore, important to maintain the hot temperature of at least 60°C in water systems and refrain from turning off the water heater. Please note; even cold water tanks can reach up to 25°C if in direct sunlight or warm environments, posing the same risk.



How to Prevent Legionnaires Disease in Hot Water Systems - https://www.smartwatertesting.co.uk/blog/post/how-to-prevent-legionnaires-disease-in-hot-water-systems
 
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There are plenty of guidelines re above but I have never seen any mention of electric showers, especially tank fed, where the temperature will often reach 20/25C in the summer and the shower is normally used at a showering temp of 38/43C and cannot exceed 48C as power to the heating elements is then cut off.
 
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IMO if it was so easy to breed legionaries in a hot water system, or electric shower, we would be hearing of infections daily. I wonder that taking a gas heated immersion cylinder as an example, the heating coil is at the boiler outlet temperature , typically 72-75oC so that water within the cylinder contacting this coil would immediately be ‘sanitised’ and as the cylinder water would be constantly moving around due to thermal currents, I wonder if all the water would eventually come into contact with the heating coil. Maybe this is why legionaries is very rare in domestic not water systems.

when I was working at one company, the maintenance dept insisted the hot water stat be set at 50oC to prevent ‘ scalding & calcium lay down, whereas the legionaries team who inspected yearly set it back to 60oC. Also all showers had to be run hot water only for 2 minutes before use. Could be this is all overkill and common sense with a scientific understanding of the risks is enough.

thanks

good point about electric showers
 
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Can’t see that any direct cylinder with a single immersion would ever reach 60 deg throughout without a destratification pump. Must be hundreds of thousands of these out there. So risks must be very low.
 
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Can’t see that any direct cylinder with a single immersion would ever reach 60 deg throughout without a destratification pump. Must be hundreds of thousands of these out there. So risks must be very low.
I agree....I think my theory of water contact with the heating coil @ 70+ oC does ‘holds water’ ( if you pardon the pun )
 

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