on adding a small amount of acid to water it s conductance increases ,in what way,does common ion effect has no role to play here

On addition of acid to water its ionic product is increases, so that conductance is increases.The common ion effect is comes under solubility products.the common ion effect is in a sprangly soluble solution if acommon ion solution is added the solubility of the sprangly soluble salt is decreses.Here water is not a solution , it is a solvent.so common ion effect is not play any role.