In some cases, the heater unit is a part of the storage tank. In others, it is a separate unit, consisting of a smaller tank with pump and heater. Regardless of the system used, the heater unit must be inspected.

It should have a burner that can be regulated to alter the intensity of heat. The burner should direct the flame into the flues, similar to the arrangement in an asphalt distributor. The pump should circulate the asphalt through the heater unit sufficiently to prevent the asphalt from burning next to the flues and from sticking (from cooling) near the outside of the tank.