Cylinder and Legionella

[omph]

If a cylinder has a high turnover, can the water temp be lowered ? Since a major contributor to Legionella growth is stale water, hence heating it above 60c. If the cylinder water has a turnover of 2-3 per day, can the temp be lowered to 30-40c ?

 

[flameport]

The temperature can be lower with high turnover if it's an unvented cylinder but 30-40 is far too low for any hot water system.

If the outlet temperature needs to be that low for safety or whatever reasons, then install TMVs at the outlets.

 

[omph]

The temperature can be lower with high turnover if it's an unvented cylinder but 30-40 is far too low for any hot water system.

If the outlet temperature needs to be that low for safety or whatever reasons, then install TMVs at the outlets.

I was thinking of adding a small unvented cylinder for the kitchen taps. 35c is usually more than enough to wash dishes.
Is there any guidance on temp and turnover ? i.e. 2 turnovers per day, min temp = 45c

 

[Johntheo5]

I think Cylinder temp should be increased to 60c once/week for legionella protection.

 

[Harry Bloomfield]

I was thinking of adding a small unvented cylinder for the kitchen taps. 35c is usually more than enough to wash dishes.

For baths or washing up, I would find 35C not very satisfactory. My cylinder is set for 60C, all the time it is on, makes washing up much easier, with proper hot water.

 

[Madrab]

Is there any guidance on temp and turnover ? i.e. 2 turnovers per day, min temp = 45c

Under current HSE guidance for domestic properties the only real advice that can be referenced is what is documented for Landlords and Legionella avoidance where stored HW should be kept at a temp of 60Deg, being the temp that legionella bacteria is destroyed. 50deg is understood to be the temp where the bacteria will start to die off so that is the min recommended in a domestic setting.

The time taken where legionella can get to dangerous levels isn't fixed and really depends on initial bacteria levels and how long it is kept at optimum temps for multiplication, that being between 20 and 45deg. It also has to be understood that it's not just the cylinder that's at risk, so is the pipework & outlets (shower heads/sprays/taps etc) where hot water is used, so that needs a regular flow of water hot enough to sanitise or a strict cleaning regime, also the removal of dead legs and a scheduled use of rarely used HW outlets to allow any bacteria to be flushed.

New lower system temps are now becoming more common with ASHP and new building standards and the current approach is that HW storage is raised to 60deg at least once week but this is a relatively new standard and in the case of ASHP's use other heat sources (boiler/immersion/solar) to supplement that requirement.

The long and the short of it is - the current standard of 60deg is currently the accepted temp for stored HW to ensure any risk of legionnaires disease is kept to a minimum.

 

[ChrisJP]

With a well insulated HW cylinder I don't see any advantage of only heating the water to 30-40C.
If it's heated to 60C then, when you need HW from a tap, you dilute it with cold to get the temp you want. So you use less of the HW supply. Thus there is little or no difference in the energy cost for 30-40C or 60C HW and, with the latter, you're sure that they'll be no probelms with legionairres disease.

 

[Mister Banks]

It’s seems like a waste of energy to heat water in the cylinder and then add cold water to cool it back down. Especially when, allegedly, there has not been a single instance of legionella reported in the UK due to a domestic water system.

 

[Harry Bloomfield]

It’s seems like a waste of energy to heat water in the cylinder and then add cold water to cool it back down. Especially when, allegedly, there has not been a single instance of legionella reported in the UK due to a domestic water system.

Equally, I simply don't see the point in the OP having is HW set at such a low temperature, barely warm at all, not even hot enough for a bath, and useless for washing up properly. If the OP is heating the water with gas, the cost is minimal.

 

[Notch7]

I found this article very useful on legionella.

On my tank the stat is about 1/3 up from bottom, I’ve found setting it to 50 deg gets the water at the taps around 60.

Personally I think in terms of legionella both cylinder stat setting and where it’s positioned, as stratification means a big temp range in the tank

Although I’m just a DIYer, so could be talking rollox

Legionella and Water Temperature: What You Need To Know

Stay informed about Legionella water temperature management! Learn about the risks in water systems and how water temperature can prevent Legionnaires' disease

www.heatgeek.com

 

[Stivino]

BBC Two - Trust Me, I'm a Doctor, Series 9, Episode 2 - What's the best way to clean your dishes?

How do you make sure your dishes are germ-free? Hot water or cool? Air drying or towel?

www.bbc.co.uk

 

[Harry Bloomfield]

BBC Two - Trust Me, I'm a Doctor, Series 9, Episode 2 - What's the best way to clean your dishes?

How do you make sure your dishes are germ-free? Hot water or cool? Air drying or towel?

www.bbc.co.uk

I disagree with part of that - liquid plus cool water doesn't remove grease. I use as hot a water as I can bare, liquid, then rinse very quickly under running cold water - idea is for there to be still some heat in the items, to speed up the draining/air drying.

 

[aveatry]

I have an unvented cylinder and in the Summer hardly use any hot water from a tap, have showers (electric ) all the time, and a dishwasher but I do make a note to heat the tank up once a week or so and the other taps in the house that are not used much do get run off too.
So in the Summer we tend to heat it up and use it until its cold and then heat up again so hopefully along with the heat the tank is also replenished enough in-between heat cycles.