The water softener discussed here relies on precipitation softening also known as ion exchange. based o hte reactants used, what ions would remain in the softened water thaat would be consumed buy the homeowners

In a precipitation softener, you will get a double replacement reaction. The calcium carbonate will be precipitated, and since the calcium salts are responsible for the hardness it will soften the water. The introduction of sodium into the water can be perilous for people who have high blood pressure, while people that have low-sodium intakes cannot use water preserved by these softeners. Other forms of softener are mostly ion-exchange based, though purification and reverse osmosis are possible selections. These tend to be affluent for collective use, as distillation entails a lot of heat, and reverse osmosis involves pumps and distinct membranes, which have to be changed frequently. 

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.