I'm quite sure that plenty of bacteria don't die at 40°, let alone ‘tap cold’.
> When a family member is sick, use hot water mixed with chlorine bleach to reduce bacteria in the bed linens and towels. The same goes for cleaning dirty cloth diapers, or other messes.
But also,
> Heating water accounts for about 90 percent of the energy needed to run a washer
So I only use heat for special occasions.
Article: https://www.consumerreports.org/washing-machines/dont-bother...
So a 40°C cloth can be washed at any lower temp but might deform or loose color or even breakdown if washed warmer than that.
> "Front-loaders and high-efficiency top-loaders run normal cycles 10 percent cooler than agitator washers, and the 'warm' wash temperature in the U.S. has declined by 15 degrees over the past 15 years," says Tracey Long, communications manager for P&G's fabric care products in North America. “Traditional detergent enzymes can be sluggish in cold water so we worked to create a mix of surfactants and enzymes that deliver cleaning performance in cold water across all product lines," says Long.
> Consumer Reports’ past tests found detergents have gotten much better at putting enzymes to work in removing dirt and stains at lower water temperatures, and are less effective at higher temperatures.
Source: Consumer Reports, "Don't Bother Using Hot Water to Wash Your Laundry: Consumer Reports' experts say cold water can get the job done", https://www.consumerreports.org/washing-machines/dont-bother...
If you want to sanitize anything, just use some bleach. It's harsh on fabric, but so is hot water, and the bleach will do a much better job. (FYI, I don't have any whites at all.)
(This might even help deal with the continually scummy front-loader problem, but I can't speak to that as we prefer our 33-year-old Kenmore top loaders that can still actually be repaired rather than replaced with expensive new Chinese/Korean crap every few years. Mechanical timer controls and durable design and mfg FTW! For what it's worth, our total cost of purchase and repairs over 33 years is maybe $1200.00 for the washer/dryer set.)