Abstract: The cast iron housing of a pump for conveying gravel or the like can be repaired by inserting into a recess in its internal surface a casting which at least substantially fills the recess. The recess develops as a result of washout, cavitation and/or other influences when the housing is in use. The casting is obtained by pouring molten metal into an impression which is formed in a mold by a pattern obtained by filling the recess with a hardenable plastic surface. The impression is overlapped by a cover having a surface which is complementary to the internal surface of the housing, and such cover is used for admission of molten metal as well as for escape of air from the impression. The casting is fastened to the housing by bolts portions of which are embedded in the casting during pouring of molten metal and extend through complementary holes of the housing or through the deepmost portion of the recess if the latter extends all the way between the internal and external surfaces of the housing.