Is this residential sidewalk (townhomes, condo's, apartments) if so you cant use 295 degree water or you will kill the grass with the water and hoses. If its commercial thats a different thing. I assume since its new its not moldy probably just tracked up with left over dirt stains, if thats the case you dont need hot water at all. Just chems to help gently lift the dirt and wash away. (woops I just saw the minimal gum part, you may need some hot water for that but not for the whole job)
Anyhow all of our washers are hot but I rarely need the hot water on new construction, it does not help with that.
Let me know what it is exactly you are cleaning and I will shoot you in the right direction with the proper materials to get the job done correctly, 99.9% of people dont have steam levers and 295 degree water, the job is already overwhelming if you have never done that much sidewalk, its way way different than a garage floor so I dont want you to feel its impossible and walk away, I do these all the time, its no biggie as long as you go into it with the proper stuff and set up correctly for time and speed. Let me know! I will check back in a few.
Another very very important thing is the type of finish on the concrete, this an overlooked area, some concrete has a rough finish and some smooth. Ask Tony Shelton, he and I took some time to look at some concerete at a local center here and ours is completely different from what he is used to seeing in Nevada. The smoothe finish will clean faster and is not as pourus, the brushed, rough or swept finish will allow dirt to go deeper into the cream coat and is more difficult to clean and easier to damage.