According to canine and feline specialists, conditioned water is not a health risk for pets.
The water softener uses ion exchange to remove the hard minerals, usually calcium and magnesium, from water. Most of the salt is used to regenerate the ion exchange beads at periodic intervals, and only a small fraction is actually added to the drinking water. Softened water typically only contains a fraction of a pet’s normal daily salt intake, the rest being present in food. Animals on salt-restricted diets, such as those with heart failure, may require salt-free water.
Hard water is also fine to give the pets. Excess minerals are just excreted out of the body and do not cause adverse health effects.