The fact specific exercise is: not {all acids} introduced into {all alkaline solutions} make for end-state simple (ie, potable) water. The result is often, water with residual mineral content. And often that is, in fact, quite toxic. EG,

Another definition of a basic salt would be a salt that contains amounts of both hydroxide and other anions. White lead is an example. It is basic lead carbonate, or lead carbonate hydroxide. These salts are insoluble and are obtained through precipitation reactions.

So good luck with that exercise.