Interactions of rainfall with surface applied P sources can result in soluble and particulate P loss through leachate and runoff. Aluminum-rich water treatment residuals (Al-WTR) are being suggested as amendments to immobilize excessive phosphorus (P) in Florida soils that sorb P poorly. This study investigated the impacts of surface applied WTR on leachate and runoff P losses. Rainfall was simulated at 7.1cm h-1 on soil boxes constructed to national protocol specifications but modified by adding a second box under the first in a double decker design to collect leachates. Four sources of P; poultry manure, Boca Raton biosolids (high water soluble P), Pompano biosolids (low water soluble P) and triple super phosphate were surface applied at two rates (56 kg P ha-1, and 224 kg ha-1) to represent low and high soil P loads typical of P-based and N-based rates. Two WTR rates (0, 1% oven dry basis) were also applied in a randomized complete block design using three replications. Soluble reactive P (SRP) loss was greater in leachate (18.5 – 706 mg) than runoff (0.4 - 96.7 mg) and in absence (1 – 706 mg) than presence (0.4 – 524 mg) of WTR. On average mass of SRP loss was reduced by ~50% in runoff and ~30% in leachate by adding WTR. Total mass of P loss from each source followed similar trends with the percentage water extractable P (PWEP) and P source coefficient (PSC) of the sources. The trend of total mass P loss of the sources (PWEP and PSC in parentheses respectively) was TSP (84%, 1) > manure (18%, 0.6) > Boca Raton biosolids (12%, 0.7) > Pompano biosolids (4%, 0.3). Thus PWEP and PSC, or their combinations, are important factors that should be integrated into the Florida P index to account for differential solubility of P sources.