Here's what I think....
and the really funny thing is about this is, I think EVERYONE is correct in nearly ALL of the previous posts!
First, I agree with others who have labeled Marc Edward's claim (quoted in post #1), as absolute hooey. The phrase "water-born outbreaks" means multiple cases, multiple houses... it's system-wide. Treatment plant failures, floods, and line breaks are the common causes. And in these "outbreaks", it's not the hot water which infects people-- NO ONE drinks hot water from the taps and fixtures! They're getting infected from the cold water. Lime and sediment deposits "grow" in water heaters. Microbial Pathogens don't.
But I also agree that HoracioO's experience is real, and it makes perfectly good sense to me. I think that he only got it wrong when creating a "theory" behind the experience. The smelly microbes aren't growing in the hot water system-- they're growing
in the clothes washer itself. Here's how: Although the water heater was set to put out 120F, the "hot" water inside the washing machine ends up being much, much colder. In the beginning, the "hot" cycle begins with a bunch of cold water pouring in from the cooled-down supply pipes. Then, when it finally does warm up, an enormous amount of heat is lost into the steel basket of the washer itself (and the valves, and the internal lines, and the clothes themselves). And because an HE front-loader uses so little water, these chilled-down issues constitute a much higher proportion of the total "hot" water being loaded into the clothes washer. (They'd be less significant in a "greedy" top loader, because the top loader would continue taking a lot more pure hot water after all of these losses have ended.)
So even at the end of the fill, it's definitely not 120F anymore. And as the wash cycle proceeds, the temperature keeps going down. So the microbes survive through the initial "pulse" heat (maybe 110F or so, maybe just 105) and as the temp continues to fall, maybe as low as 100, they're having a party-- it's like a whirlpool bath for the little buggers.
Over time, they grow into a big colony and create a mat of smelly organic muck. And once it's grown up, the thick mat further protects them from the initial "pulse" of high temperature at the end of the wash cycle fill.
In this scenario, bringing the water heater up to 140F brings death to the buggers-- you've got enough heat that even with all the losses in the pipes, valves, basket, and clothes, it's still killing them, and it eats away at the mat over time. Clean clothes washer!
- - - - -
I must disagree with just one thing in the post above (from prd823): He's right on the money about using too much detergent, but he might be wrong to recommend powders. In some machines, the detergent-loading compartment gets rinsed many times, and that helps some-- but once the powder chunks have washed down into the basket, HE front loaders use only gravity to agitate the contents, and they
must be used with low suds formulas, because the water volume is so small. A regular powder detergent suds too much, and the excess suds don't rinse off properly. Because of the low water volume, HE front loaders also make the washing solution much muddier with dirt and grime-- and the good HE detergents are formulated to suspend the higher degree of filth better. Just as they failed with their own suds, the regular detergents will leave dirt behind-- they just can't keep it suspended. So you end up needing two or 3 rinse cycles, which kind of negates the whole purpose of buying "High Efficiency" in the first place.
In my washer, which is very high-end, I tried it and looked. Powder remains undissolved for 5+ minutes at high temps, and remains undissolved through the entire washing stage in the cold/delicate cycle. The one which always works well is
Tide HE liquid. "All" doesn't work as well. There might be some other good HE products, but my DW needs fragrance-free, and there are very few options.
prd823 is totally
RIGHT ON! about the amount of detergent. With Tide HE, we've found that the best results come from using less than 1/3 the amount of the "normal load" line on the cap-- even though our clothes washer is one of the biggest front loaders which sold for non-commerical use, and even when we've filled it really filthy towels from construction clean-up. It isn't "just as good" as using the Tide-recommended amount: it's much, MUCH better to use far less. Cleaner clothes! Cleaner washing machine! Less detergent down the sewer for water treatment! Less Money! Less Shopping! Less totally wins.
So my advice is HE liquid, no powders, at about 1/4 the recommended amount. (Just like prd823 said-- in a normal load, that's about 2 tablespoons.) And for you, keep that WH temp up at 140F- you're clearly doing the right thing by leaving it there.