A 4-component model for settling slurry pipeline friction loss has been previously described by Wilson and Sellgren. The goal of the present work is to adapt the concepts of this model to the calculation of centrifugal slurry pump performance deratings (i.e. pump solids effect). Tests were carried out using four different graded silica and crushed granite products representing the four model components. These were then combined and tested in permutations from the individual components to the complete mixture at various concentrations. Closed-loop run times were limited to minimize solids degradation. Primary experiments were carried out using a GIW 8×10 LSA-32 pump and selected corresponding experiments were repeated using a smaller GIW 3×4 LCC-12 pump. In all, 40 tests were performed with particle sizes ranging from minus 40 μm to 12.5 mm, dso particle sizes from minus 40 um to 7.5 mm, and delivered solids concentrations from 4% to 38% by volume. Particle size distributions varied from very narrow to very broad, with d85/d50 ratios ranging from 1.3 to 30. A new 4-component model for the pump Head Reduction Factor (solids effect on head) is proposed and compared with the existing mono-sized model described in the Centrifugal Slurry Pump Standard ANSI/HI 12.1-12.6-2016.