Can someone please explain this gas water heater thermostat marking
So, according to a manual I was able to finally find, the box with a slash through it indicates 120F (similar to the triangle commonly seen). Each marking above that represents a 10F increase in water temperature. I am going to guess that they wanted to indicate a scald free setting and a typical setting differently; my understanding is that 120F does not sanitize, but 130F will.