do not want to blow face off

How hot does the floor of the heat bell get. My riser sits on a fire brick. The firebrick sits on the floor of the heat bell. In my haste I burried a 3/8 inch 20 ft copper coil 2 inches below the floor packed with cob and small rocks, so I could heat water. I was going to have an elevated water barrel ( 18 inch rise) and hook up two pipes from the barrel to feed the coil. I have good ideas, but sometimes lack the thinking it thru part. Is the temperature in the floor too high? Will I blow my face off? Help me Obiwan, your my only hope. I hope my description is good enough, I can explain further.

Just so you know Im for real, here is a picture. note the copper feeds sticking out. As you can see, I used scrap tile and stone from some of my jobs. I mined the clay from my crawl space. This whole project has given me a primitive satisfaction of working with the earth. I think cob is my new favorite medium!!! Hopefully some one can enlighten me on the water/coil deal. Id buy the 4 disc dvd set, but I am extremely poor rt now. Take care all.

Looks cool! Check out Donkeys Rocket Stove boards for more water heating expertise.