We consider the N=1 superpotential generated in type-II orientifold models by non-geometric fluxes. In particular, we consider the family of P fluxes, that are related by T-duality transformations to the S-dual of the Q flux. We determine the rule that transforms a given flux in this family under a single T-duality transformation. This allows to derive a complete expression for the superpotential for both the IIA and the IIB theory for the particular case of a T^6/[Z_2xZ_2] orientifold. We then consider the tadpoles induced by these fluxes, and we determine all the exotic branes that have to be introduced in order to cancel them. This is achieved by determining a universal transformation rule under T-duality satisfied by all the branes and generalised KK monopoles in string theory.
