I don’t care if there is some bacteria on my pants – I wash my hands before I eat, and (at least where I live) nothing exists that is going to burrow through the skin on my knees to infect me.
For clothing, clean = not dirty. I don’t need clothing to be medically sterile, and I prefer not to contribute to the creation of superbugs by trying to kill everything in my environment.

I can see why in some washing machines, cold water doesn’t do as well. But in mine, I haven’t noticed any difference from switching to cold.
I would feel perfectly comfortable sleeping in motel sheets washed in cold water. I might prefer that they be bleached, but I don’t care about the heat. Even if I was highly concerned about motel linens, there’s a huge difference between the kind of washing I want done when sleeping where others have slept, and the kind of washing I need to do to clothing which has simply been on my own body for a day.
I *have* noticed a difference in whites, but hot water didn’t fix it, so it might just need bleach. As my ‘whites load’ is merely one t-shirt, I have taken no action to rectify this problem.

Why is this an all-or-nothing for so many people? The point is that for a lot of people, at least some loads don’t need to be washed in hot water to be sufficiently clean for the needs. That doesn’t mean you have to defend your diaper-washing regimen…

I would be interested to see how much of a difference it really makes. Theoretically it makes a difference… yes… but HOW MUCH? I mean are we talking 10% difference?… 1% difference… 0.001% difference?

Assuming the water temperature and viscosity impacts the dry time to a measurable amount then I would think the simple solution to that would be to just spin the clothes a little more. Increased spin time would not be much difference and would cost very little. It wouldn’t be hard at all to setup the spin cycle to to spin the clothes until X amount of water is removed. Or they may just set the spin cycle to spin for more than enough time to make sure as much water is removed as possible no matter the water temperature. e.g. if we know that a typical load of laundry washed at 60C temperature takes 5 minutes of spin to get as much water out as possible and you would have to spin it 10 minutes to get all the water out if its 40C then they may just build washers to always spin 15 minutes. The ‘overkill’ system.

Generally they don’t cause a problem, especially if you practice good basic hygiene (washing hands after using the washroom and at intervals during the day, using a fresh dish cloth and avoiding cross-contamination in the kitchen, etc). In fact, coming into regular contact with bacteria and viruses is good for most people; it helps keep your immune system in good working order.

There are thresholds for levels of certain types, for instance fecal coliform bacteria, and there are some types of bacteria that are more likely to make you sick, but in general simple counts of the number of bacteria on a surface doesn’t tell us much. The type of bacteria is much more important than the number.

Like I said, for the vast majority of people, using regular (non-antibacterial) soap and water and regular detergent in cold water will keep things under control and within the range of what our immune systems can handle on a daily basis.

I did change my detergent, multiple times, and yes, I used the cold water formula. No change. The only thing that worked was using hot/warm water.

A phrase that has always stuck in my mind is: “The solution to pollution is dilution.” In other words, short of an operating room, the goal is not to create a sterile environment, but to reduce the number of nasties to a level that your immune system can handle without becoming overloaded (sick).

Even for soiled cloth diapers, I would think that soaking and bleach would be more effective than hot-water wash.

According to this article, washing everything in cold or cool water put your family at risk from fecal germs and the norovirus remaining on clothes, but the machine itself becomes contaminated. The council recommends that all clothes, linens and other fabrics should be laundered at a high temperature — i.e., 60c (140F) — to be sure bacteria, viruses and dust mites have been destroyed

40 degrees celsius is 104F (will kill some germs); 60 degrees celsius is 140F (even better). And maximize the wash time & use higher heat for drying, according to a biologist friend of mine.

I wash in cold water and definitely do a lot of re-wearing before washing my own clothes. I have found a lot variation between detergents, though — there are some that left my whites a little bit dingy after a few washings. Fortunately I found one that works very well in cold water.

Change your detergent.

Some detergents are specially-forumulated for cold water. You were likely using one that wasn’t, and expected it to work the same in cold water as it did in warm. Hence, splotches.

(Re: Wearing clothes more than once)

I agree, for the most part. I’ll wear shirts twice before washing. I’ll wear a pair of pants all week.

But underwear is strictly a one-wear item. I actually go through at least 2 pair a day (I go to the gym after work, and can’t bring myself to re-wear the pair I’ve already had on all morning).

I’d never thought about it before, and it sounded like nonsense to me at first, but I looked it up, and it makes sense – the viscosity of any liquid changes with temperature. You know how when you heat syrup or honey it gets thinner? It’s the same for water. You don’t notice it because water is so thin to begin with, but on tiny size scales – like the spaces between the threads in your clothes – it makes more of a difference. So the spin cycle should be able to get more of the water out when you rinse in warm water, so the dryer has less to do.

(If you want to get into the physics-nerdy details, look up “Reynolds numbers.”)

And, warm water is more fluid? (comment #13) Maybe it doesn’t take quite as much heat to dry, but that would only be a small marginal decrease.

Our dryer runs based on time, not dampness of the clothes (I know, new ones have sensors), but I’m guessing the dampness and drying time isn’t impacted all that much between water temps.

I can’t believe the difference it made in our son’s allergies when I started washing EVERYTHING in hot. He’s highly allergic to dust mites and it has allowed him to stop having to take Zyrtec daily. His sheets are washed weekly and we have gone fiber free otherwise in him room! It had never occurred to me that his clothes – stored in the closet of the same room he slept in would be contaminated with dust mites, but they apparently were.

I’ll take the <$5 increase on our gas bill (I went from running 2 hots loads – sheets & towels – to running 7 hot loads a week, so about 28 loads a month) and buying clothes slightly more often. I also noted that stains on my kids play clothes that had been washed multiple times on cold (with Tide!) suddenly disappeared also.

Bottom line – if you want CLEAN – not just "not dirty" – clothes, you need to wash on hot and dry on hot.