Floor goes in tomorrow

Diiferent construction practices throughout the country. Here, we are putting in a walkout  basement and the framer wants the floor in before he starts to frame. The plumber got the infloor heat pipe in this morning. I had finished putting in the styrofoam on the weekend and we pour tomorrow. We have been praying for no rain because I didn't want a bunch of water trapped in the basement above the poly and looks like we are going to be in good shape. We ran 1/2 line (PEX)  through the basement floor area and roughed it in to the mechanical room. Now I have the option of doing something with it after we move in. I want some combination of solar heat to preheat for the water heater and running the infloor heat off the water heater. More research required but now I have the option.