On 16/04/2012 07:06, harry wrote:
> On Apr 15, 9:58 pm, John Rumm<see.my.signat...@nowhere.null> wrote:
>> On 15/04/2012 20:21, Tim wrote:
>>>> Well if they're only turning the circ pump on intermiitantly when
>>>> water is required the water will cool and legionella is what they'll
>>>> get. Whether they catch it of not is another matter.
>>>> An ideal system for breeding it.
>>> You mean just like a conventional system when you turn off the hot tap
>>> leaving a long "dead leg" of water cooling?
>>> Can't see why it would be much worse with a circulator.
>> It would actually be better, especially if you blended it down to final
>> mix temperature at the point of use - since you would be periodically
>> raising all the pipework to full temperature.
> You need a temperature of 80-90degC to kill off legionella. The
> normal 60-70 is not enough.
Note also many boilers with capabilities for split temperature operation
also allow for routing anti legionella cycles to ensure the system is
heated to a higher temperature at least once a week.
> The best you can hope to do is to flush it away in a domestic system.
Since it is easy to kill, why?
> But what happens with a circulator is that you pump it back into the
> So instead of just having it confined in a "dead leg", you have it in
> the whole system.
If its there, its in the whole system anyway. A circulation loop
eliminates any deadlegs on infrequently used hot taps, and thus reduces
the possibility of breeding happening there.
> So water in the DHW loop cools, you may get legionella breeding , pump
> starts, sends the polluted waterback to the tank and pollutes the
> whole system.
Mixes with the hot water and dies...
> Wonderful eh?
> Legionella breeds best at around human body temperature,
Is your body routinely at the 60 - 70 one would run a cylinder at?