This report discusses the Production Test 105-2-P (Supplement A) -- Activity of Pile Discharge Water. Previous studies of pile discharge water have shown that one of two processes is responsible for the large but variable amount of Mn{sup 56} activity present in the water. One process is the production of Mn{sup 56} by the reaction Mn{sup 55} on manganese impurity in the water. The amount of such impurity has been shown to be too small to produce the observed amount of Mn{sup 56} unless the mean irradiation time is increased by a large factor due to temporary sticking of manganese on the surfaces in the tubes. The other process is the production by the reaction Fe{sup 56} on iron in the film. The present production test was designed to determine which of these processes is responsible for the troublesome Mn{sup 56} activity and to what extent the activity is increased due to sticking of manganese or iron in the tubes. 4 figs.