Low energy lifestyle - in case it helps

Section62

Auti said:

Hi, sorry for my not understanding of legionella and I am getting more confused and worried (autistic). I use gas to heat water in a tank (I have yet to find out if it is fed directly from mains water or from a storage tank, there is a little plastic box type thing with water in the loft which I think the man said was an expansion tank - it is small) and it is set to 50 degrees for safety temperature wise. I heat once a week using the hot water button on the programmer rather than setting timer for it to come on and go off. I use water for my child‘s shallow bath and then for my shallow bath about 2/3 hours after it has been heated. The next day I use the hot tap and the hot/warm water to wash my hair and hand wash clothes. My questions are: If my tank is fed directly from the mains is there any risk of legionella as it is treated water from the  mains? But, if my tank is fed from this plastic box (no idea where this water is coming from) am I putting myself and child at risk of Legionella? What also of using the cooled down water on the subsequent days given legionella can grow in pipes etc, is that dangerous too? I am getting to the point I should use a kettle for everything and now worried about washing clothes at low temperatures as legionella will be on them. Sorry for my not understanding but everything is now becoming scary as trying to be frugal but now maybe putting my child and me at risk of serious illness.

Try not to worry. It doesn't matter much whether the hot water tank is fed directly from the mains or a tank in the loft.  The key point is heating the water to 50C should kill any legionella present.

If you then let the hot water tank cool down then even if they were some legionella present, they will become dormant when the temperature drops below 20C.

The golden rule is to keep hot water hot and cold water cold.  You are achieving that, albeit on a weekly cycle.

ariarnia

Section62 said:

Auti said:

Hi, sorry for my not understanding of legionella and I am getting more confused and worried (autistic). I use gas to heat water in a tank (I have yet to find out if it is fed directly from mains water or from a storage tank, there is a little plastic box type thing with water in the loft which I think the man said was an expansion tank - it is small) and it is set to 50 degrees for safety temperature wise. I heat once a week using the hot water button on the programmer rather than setting timer for it to come on and go off. I use water for my child‘s shallow bath and then for my shallow bath about 2/3 hours after it has been heated. The next day I use the hot tap and the hot/warm water to wash my hair and hand wash clothes. My questions are: If my tank is fed directly from the mains is there any risk of legionella as it is treated water from the  mains? But, if my tank is fed from this plastic box (no idea where this water is coming from) am I putting myself and child at risk of Legionella? What also of using the cooled down water on the subsequent days given legionella can grow in pipes etc, is that dangerous too? I am getting to the point I should use a kettle for everything and now worried about washing clothes at low temperatures as legionella will be on them. Sorry for my not understanding but everything is now becoming scary as trying to be frugal but now maybe putting my child and me at risk of serious illness.

Try not to worry. It doesn't matter much whether the hot water tank is fed directly from the mains or a tank in the loft.  The key point is heating the water to 50C should kill any legionella present.

If you then let the hot water tank cool down then even if they were some legionella present, they will become dormant when the temperature drops below 20C.

The golden rule is to keep hot water hot and cold water cold.  You are achieving that, albeit on a weekly cycle.

just mentioned this bit of the thread to the OH. he's said as far as he knows there's not much issue with combi boilers because the water coming in from the mains (cold) is chlorinated and it doesn't hang around before its heated for use. when you heat chlorinated water or let it stand the chlorine filters out and that's why water tanks kept at below 60 are a risk. not that there might be legionella in the water when its coming into the house. according to himself anyway. i guess if you left it standing in the pipes for a long time that might be a problem. so maybe if you're like the poster who goes away for 4 months of the year you might want to run the taps for a bit when you get home?

wrf12345

If you are going away for three months I would drain the system before going, esp as it is unlikely to be covered by insurance. 

Section62

ariarnia said:

just mentioned this bit of the thread to the OH. he's said as far as he knows there's not much issue with combi boilers because the water coming in from the mains (cold) is chlorinated and it doesn't hang around before its heated for use. when you heat chlorinated water or let it stand the chlorine filters out and that's why water tanks kept at below 60 are a risk. not that there might be legionella in the water when its coming into the house. according to himself anyway. i guess if you left it standing in the pipes for a long time that might be a problem. so maybe if you're like the poster who goes away for 4 months of the year you might want to run the taps for a bit when you get home?

Chlorination (or other disinfection) at the treatment works should kill legionella in that water, but it doesn't guarantee that the water arriving at your property is legionella-free.  Most people's water supply comes via a storage tank (typically underground reservoirs in towns, water towers in rural areas) and pipework which may be a source of legionella in water which no longer has a disinfection concentration high enough to kill it. (although if kept below 20C the legionella should be dormant).

In normal use the water in a domestic cold water storage tank should be getting topped up regularly with fresh (chlorinated) mains water, which in theory would keep the storage tank legionella free - if it is assumed that mains water is inherently legionella-safe.  In practice that's not guaranteed.

I agree with your OH that there's not much issue with combi boilers - but with a bit more emphasis on the 'much'.

That's the point I was making to Planeteer - the issue with legionella is about temperature and time, there's nothing about a combi system which makes it inherently safe vs a storage system.  It comes down to the way in which the hot water system is used in practice.

Planeteer

wrf12345 said:

If you are going away for three months I would drain the system before going, esp as it is unlikely to be covered by insurance. 

Are you talking about draining the rads, or the water supply pipes? I only have a main water type (in the loft for some reason) which I have never touched, tbh, but don't know how to drain any water supply pipes?