The exhausted permutit is generally regenerated by percolating through it a solution of:

The temporary hardness or carbonate hardness is due to the soluble $\mathrm{Ca}({\mathrm{HCO}}_3{)}_2$ and $\mathrm{Mg}({\mathrm{HCO}}_3{)}_2$ . The permanent non-carbonate hardness is due to ${\mathrm{CaCl}}_2, {\mathrm{MgCl}}_2, {\mathrm{CaSO}}_4$ and ${\mathrm{MgSO}}_4$. The process of removal of ${\mathrm{Ca}}^{2+}$ or ${\mathrm{Mg}}^{2+}$ ions is called softening of water.

Which is not present in clear hard water?`

The temporary hardness or carbonate hardness is due to presence of soluble $\mathrm{Ca}({\mathrm{HCO}}_3{)}_2$ and $\mathrm{Mg}({\mathrm{HCO}}_3{)}_2$. The permanent non-carbonate hardness is due to  ${\mathrm{CaCl}}_2, {\mathrm{MgCl}}_2, {\mathrm{CaSO}}_4$ and ${\mathrm{MgSO}}_4$. The process of the removal of ${\mathrm{Ca}}^{2+}$ or ${\mathrm{Mg}}^{2+}$ ions is called the softening of water.