Some dishwashers can boost the water temperature. Another case of contradictory legal mandates. For burn safety for children / elderly / not fully adult competent, my state law requires that domestic hot water heaters be set no higher than 125°F when installed, and when unit occupancy changes. Occupants are free to push the setting higher, but installers and landlords mustn't do it.
Factory default for Takagi instant heaters is 122f. My newish Sears 30gal short tank has 108f as default setting. Above 130f mineral slag and scale start to form or build up. 140f minimum for food service chemical sanitized dishes. 180f if using just hot water to sanitize. No way you can hand wash at 140f or even maintain that temp in the sink for very long. Looks good on paper or at some lab but just doesn't work in the real world. "For burn safety for children / elderly / not fully adult competent, my state law requires that domestic hot water heaters be set no higher than 125°F when installed, and when unit occupancy changes. Occupants are free to push the setting higher, but installers and landlords mustn't do it." There should be or is a dual requirement to have temp regulating mixing valves so you can have the high temp and be scald safe at the same time. That said I have yet to see a plumbing guy do the installation temp adjustment for these properly. Fingermometer and/or just screw the handle on and forget it.
Yes, some can. But why don't all of them? Then the domestic water could be set at a safer temperature that would prevent scalding, and we'd all be healthier and use less energy. Sounds like an obvious solution to me. I wonder how many years it will take to either educate the population, or have it mandated into law.
Here is what the CDC has to say on the subject: Legionella Infection Risk from Domestic Hot Water - Vol. 10 No. 3 - March 2004 - Emerging Infectious Disease journal - CDC But read the whole thing if you are concerned. (Not for the faint of heart.)
I installed my water heater on the back of the shower enclosure upstairs, there is less than 3 feet of pipe to the valve, then about 3 feet to the shower head. Yellow is gas, Blue/steel is cold, Red is hot, White is Pressure relief, grey is the line to the shower head/faucet
If you have city water, there should be enough chlorine to kill bacteria. It's a valid concern for well water, however. In any case, if you're worried but still want to save energy, you can rig a controller to heat it up to 140F a few times a week (perhaps an hour or two before you normally use the dishwasher), but drop it to a lower value like 110F most of the time.
