Means for cleaning heat conductive conduits in a heat exchanger which comprises an inlet conduit for introducing cooling water and an outlet conduit for exhausting the cooling water, said cleaning means including means provided in said cooling water outlet conduit for recovering resilient balls, means for separating the resilient balls from the cooling water, fluid driven pump means for drawing cooling water containing the resilient balls, means for introducing the resilient balls into the conduits, and further conduits for connecting the cooling water inlet conduit with the other components of the cleaning means.