Lowering water boiler temperature - health hazards?

ioealshk

I've got an old type two chamber copper water boiler that feeds my bathroom hot water tap. In the past I used to let it sit until the the water reached near boiling temperatures, but since the April price hike I decided not to waste the energy and tried to make sure that I only keep it for half an hour which was enough to bring the water to the right shower temperature. However because I was rubbish with keeping an eye on the time, I often let it run for longer, so in the end I turned the thermostat to 120 Fahrenheit (which turned out to be about 45 normal degrees). So now if I forget to switch the boiler off after 30 minutes the thermostat does it for me (and then I switch it off in the next 15-30 minutes).

However, I remember reading that a reason the boilers are set to heat the water to such high temperatures is to prevent bacteria, namely legionella, from growing inside the tank.

Does anyone know if that's true? How much of a risk is it to keep my water tank at 45 degrees as most? Or should I bring it up to the near boiling temperature maybe once a week as a safety measure?

Vincero

Yes legionella is the main concern. 60-65°C should be a safe temperature range to avoid it.

If that is proving too hot or the mixing tap for the shower or sinks around the house, you can get a thermostatic mixing valve (TMV) added near the cylinder which will mix the hot and cool water to provide around 45°C.

matelodave

No it's not a health hazard if you occasionally heat the water to 60-65 degrees a couple of times a month. You dont need to keep at 60 all the time, nor do you need to boil it

Our heatpump only heats to 45 degrees and boosts it to 60 for ten minutes on Saturdays.

Section62

Vincero said:

If that is proving too hot or the mixing tap for the shower or sinks around the house, you can get a thermostatic mixing valve (TMV) added near the cylinder which will mix the hot and cool water to provide around 45°C.

TMV's - if used - should be located as close as possible to the point of use, not the source of heat or storage.

EcoScruples

I'm sorry but that's actually some really bad advice.
There's an approved code of practice by the HSE that advises you heat hot water storage tanks to 60 degrees for a min of 1 hour on a daily basis to eliminate the risk to legionella growth.
If you're running your tank at 45 degrees for a week then you're promoting the perfect conditions for bacterial growth.

Ally_E.

EcoScruples said:

I'm sorry but that's actually some really bad advice.
There's an approved code of practice by the HSE that advises you heat hot water storage tanks to 60 degrees for a min of 1 hour on a daily basis to eliminate the risk to legionella growth.
If you're running your tank at 45 degrees for a week then you're promoting the perfect conditions for bacterial growth.

And then you kill all of that bacteria with 60C once a week. 

wild666

I'm running my hot water at 50 degrees all the time. I use the kettle to boil water for drinks and washing up and put about 4 titres of cold water into 1.7 litres of boiling water it hasn't had any effect on me since I lowered the temperatures in September 2021.

EcoScruples

Ally_E. said:

EcoScruples said:

I'm sorry but that's actually some really bad advice.
There's an approved code of practice by the HSE that advises you heat hot water storage tanks to 60 degrees for a min of 1 hour on a daily basis to eliminate the risk to legionella growth.
If you're running your tank at 45 degrees for a week then you're promoting the perfect conditions for bacterial growth.

And then you kill all of that bacteria with 60C once a week. 

Yes you do and that's fine if you use no water until you kill it, you see my point?
The risk is going to be low to medium so generally most people won't see any ill effects but to mitigate the risk the temp needs to be regularly maintained at 60 degrees.

People do contract legionella but not in huge numbers, it's mostly from hot water systems that supply showers that create that mist where the droplets can be breathed into the lungs. 
Running taps and having a bath is going to be very low risk.
As I have to maintain hot water systems at work under the HSE regs I'm extra cautious than most at home.

Ally_E.

EcoScruples said:

Ally_E. said:

EcoScruples said:

I'm sorry but that's actually some really bad advice.
There's an approved code of practice by the HSE that advises you heat hot water storage tanks to 60 degrees for a min of 1 hour on a daily basis to eliminate the risk to legionella growth.
If you're running your tank at 45 degrees for a week then you're promoting the perfect conditions for bacterial growth.

And then you kill all of that bacteria with 60C once a week. 

Yes you do and that's fine if you use no water until you kill it, you see my point?
The risk is going to be low to medium so generally most people won't see any ill effects but to mitigate the risk the temp needs to be regularly maintained at 60 degrees.

People do contract legionella but not in huge numbers, it's mostly from hot water systems that supply showers that create that mist where the droplets can be breathed into the lungs. 
Running taps and having a bath is going to be very low risk.
As I have to maintain hot water systems at work under the HSE regs I'm extra cautious than most at home.

I understand it from HSE point of view, however surely it takes bacteria time to develop. It won't be there an hour after the temp dropped below 60C. And isn't legionella killed at 50C too just over a period of 2 hours instead of 2min when it's at 60C?

Vincero

Section62 said:

TMV's - if used - should be located as close as possible to the point of use, not the source of heat or storage.

It's possible I've seen a bodge where it's been used before near cylinder to avoid using multiple of them and also to avoid needing additional check valves by using the hot water feed and the cool water from the header tank...
As always, one should consult a reputable plumber or if doing the work themselves RTFM.

EcoScruples

Above 45 degrees will do it and if you turn your water over regularly then that also lowers the risk.
The bacteria will potentially populate over a few days if water is stored at between 20 to 45 degrees.
I just couldn't advise anyone to run their tanks at 45 degrees for long usage periods thats all. 
In my eyes it's better to remove the risk completely. I'd rather spend a bit more on electric if it meant myself and my family had no risk from legionella at all.