On Fri, 17 Jul 2015 15:08:49 +0100, Chris French wrote:

snippage

And unless the clothing has been exposed to some significant nasty, I'm
not sure what we are supposed to be catching from clothes washed at 30C
or whatever (and again, surely the detergent will get most of them?)

A lot of the clothing I have is limited, on the label, to 40C; some to 30C,
so a higher temperature would risk damaging them.
The bedding and some clothes are rated for 60C - that's not high enough to
kill the nasties.
Now, I can't recall the exact temperature, but ISTR that the water samples I
used to test for bacteria were incubated at somewhere close to 40C as being
the ideal temperature for the bacteria to multiply. This seem to make 40C
the worst temperatu doesn't kill and does encourage bacteria whilst using
significant energy(1).
At 30C, it's about the same as the clothes would be when worn as a single
layer, so no change; at 20C, if the detergent does work well(2), the energy
is much less than at 40C (obviuosly) and the bugs will be "out of their
comfort zone" (sorry).

(1) Sadly, I log the energy per wash. The difference between 30C and 40C,
with the smae loading and close in time so that the incoming water will be
about the same, is around 35%.

(2) In Asda t'other day (sorry again - looking at LED lamps, honest) the
own-brand non-bio powder boasted of being suitable for 15C. A recent wash at
20C used about 30% of the energy of a 30C one, although I didn't see the
current go up to indicate the heaters being on, but I might have missed it.
--
Peter.
The gods will stay away
whilst religions hold sway