Why do firefighters recommend the use of a deluging volume of water when extinguishing an oxidizer-supported fire

Why do firefighters recommend the use of a deluging volume of water when extinguishing an oxidizer-supported fire? What may happen to a large (i.e., 30-50lb) container of trichloro-s-triazinetrione, or calcium hypochlorite, if it is left to sit in the water and muck remaining in a building after fire fighting efforts have ended, but clean-up will not begin for several days? The assumption here is that the plastic container has been compromised in some way by the heat of the fire and possibly creating cracks in the base or sides.