Internal Stainless Steel Coil (shown connected to our Aluminum Water Holding Tank).  The coil allows water to circulate through the burn box and heat the water tank continuously! To be attached to our 12 Gallon Water Tank or a standard 30 gallon water tank that you provide. Have lots of warm water on hand for bathing! Order one with your stove today! Can be positioned to either the left or right rear of the stove, an elbow pipe can allow the coils to be plumbed to the side rather than the rear of the stove (also illustrated in the photo).