Abstract: A pipe connecting structure for a heat exchanger having a header portion or manifold defined by a plurality of parallel elongate header tubes, connector block having a side face adapted to abut against a side region of an outer one of the header tubes and connection means configured to connect a pipe thereto, and joining means. The joining means include at least one elongate tubular member having a first end adapted to be inserted through a hole formed in a first side wall of at least the outer one of the header tubes, and a second end extending through a corresponding hole in the side face of the connector block, whereby the second end communicates with the connection means.