Permutit is also known as zeolite. When a sample of hardwater is percolated through a bed of powdered permutit the following base exchange reaxtion takes place making the sample of water soft.
 2Na-permutit + Ca${}^{+2}$ → Ca (permutit)2 + 2Na${}^{+}$.
 The ions Ca${}^{+2}$ causing hardness to water are absorbed by permutit releasing releasing Na${}^{+}$ and hardness is removed. When all the Na site in permutit is replaced by Ca${}^{+2}$