A method of installing plumbing in a building, comprising the use of a plumbing support panel that enables outlet pipes and other plumbing pipes to be pre-assembled at the correct relative position with respect to each other for the installation of fixtures, and installed as a unit by mounting the panel to studs or to other parts of a building's structure. The panel comprises holes through which outlet pipes may be installed and mounting holes for the installation of pipe clamps to hold the pipes in place and for the mounting of the panel to a building's structure.