Abstract: Disclosed is a piston for a water pump, e.g., a pressure washer pump. The piston includes a piston body and a piston head and in the improvement, the piston body is solid, homogeneous ceramic. That is, the piston body has a generally cylindrical surface and the body is circumscribed by the surface and is homogeneous ceramic. A method for making a piston for a water pump includes the steps of providing a piston body made of a ceramic material, and making a piston head of steel and having a pocket formed therein. The head is heated, the pocket and the body are engaged in overlapping relationship and the head is allowed to cool and "shrink-fit" to the piston body. The piston head is formed to have a relief groove circumscribing the pocket for reducing compression forces resulting from such cooling.