Abstract: A water boiler adapted for use in a fireplace is disclosed having an inlet header pipe, an outlet header pipe, and a series of pipes disposed parallel to one another and connected between the inlet and the outlet header pipes. The series of pipes is fashioned so as to form a grate suitable for supporting a log fire, including a horizontal portion upon which the logs may be supported and a remaining portion which extends upward along the rear wall of the fireplace through an arc back toward the top front of the fireplace, whereby heat rising from the fire passes between the series of pipes for added boiler efficiency.A heating system using the fireplace boiler and operating in conjunction with a conventional residential heating system is also disclosed. The fireplace boiler contributes heat a conventional furnace to reduce the amount of energy consumed by the latter.