Thank you all for your input! Very informative. Alex Chernov seems to be the masonry heater expert. He designed an experimental heater/boiler for a shop in Perth Ontario. Look at Lopez Labs Masonry Hydronic Heating, great series of photos and some early resuts. This system seems like what I envisioned, although I would want a water/heat storage tank. I thought a well insulated 200 gal tank would do, but the plumbing, need guidance. I need a basic, safe system. Heater/boiler to tank, safety valve location/s, circulatory pump, size of lines, heat dump to garage from tank…