My project is to heat a cast concrete counter top. I want to thermostatically control the temperature. I would like to circulate through my Hot Water boiler. I want to achieve this result as inexpensively as possible. I plan to use 1/4" O.D. PEX within the cast. If I tie in the ability to back flush the system I am hoping that I can avoid the heat exchanging expense. I am hoping to be able to tap into the DHW supply with a small inline pump thermostatically controlled and return directly to boiler. I am not a plumber but I hope you can appreciate my project and give helpful suggestion. Thank You very much!