I have to launder a bunch of really dirty stuff. Is there any reason I shouldn't crank the temperature on my hot water heater all the way up? Half of me thinks that's completely nuts and something would surely explode, but the other half of me thinks it must be fine or they wouldn't put those settings on the hot water heater. I've got a 60 gallon natural gas tank that is only a few months old. I figure it would just take a few hours to heat up and then I could put it back. What do you think?
The only real danger in turning up the thermostat on your water heater is that you greatly increase the risk of scalding. Most water heaters will come from the factory with the thermostat set at 120 deg. F. I keep mine set at 130 deg. F. If you have small children or mentally challenged people in your family, it's best to keep your water heater temperature down so that they don't accidentally scald themselves. If it's all mature responsible adults in your household, then I'd say go for it. Just be more careful with that hotter water.
The higher temperatures WILL shorten the lifespan of your water heater a bit. That's because the lifespan of a water heater is largely determined by the lifespan of the porcelain enameled tank inside it, and the lifespan of that tank is determined by the lifespan of that porcelain enamel coating on the inside of the tank (which is similar to the porcelain enamel coating on a steel bath tub). The lifespan of that coating is largely determined by the cumulative "thermal shocking" the coating receives. The higher the temperature of the water in the tank, and the greater the drop in temperature when new cold water comes in to replace hot water drawn out, the greater the thermal shocking the porcelain enamel coating receives, and the sooner it will crack and expose the metal walls of the tank to water, and hence corrosion. This is why a larger tank that has smaller temperature drops will last longer than a smaller tank with larger temperature drops.
You don't have to worry about your tank exploding. It will be fitted with a Temperature and Pressure relief valve that will open if EITHER the temperature or pressure inside the tank become too high. I haven't had a gas fired water heater in nearly 10 years now, but if I recall correctly, the T&P Relief valve will open at either 200 deg. F or 150 psi, whichever comes first.