You are using a thermostat with the uth? Right???!!! I would assume you also have a fail safe Tstat running as well? I hope so. This method is fraught with risk. Liquids, out gassing, fire hazards. I hope you are using a waterproof UTH that is designed not to outgas and low temp? I have serious concerns about using a pad that specifically states it requires air flow across it for safe use.