The major products during the removal of temporary hardness of water are

Temporary hardness of water is removed by Clark's Process and in Clark's process, slaked lime $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$ is added to hard water.

Clark's process involves the addition of a controlled quantity of slaked lime (calcium hydroxide) into the hard water

$\mathrm{Mg}{\left({\mathrm{HCO}}_3\right)}_2\left(\mathrm{aq}\right)+\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)\to {\mathrm{CaCO}}_3\left(\mathrm{s}\right)+{\mathrm{MgCO}}_3+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Insoluble calcium and magnesium carbonates precipitated out as end products of the reaction and no longer cause hardness.

Slaked lime is itself a source of calcium ions (and hence hardness) so care must be taken to avoid adding in excess quantity.