A cleaning system for cleaning the interior of a boiler wherein the system includes a cleaning solution reservoir adapted for mounting within an appliance in which the boiler is housed, and a flow conduit circuit having eductor means operative to draw cleaning solution from the reservoir and pass it to the interior of the associated boiler when water under pressure is introduced into the eductor. The system finds particular application in descaling boilers employed in steam cooking ovens and the like wherein the boilers are relatively inaccessible.