Homemade Washing Soda | Penniless Parenting
Calcium Carbonate CaCO3 effects the hardness of the water. If the water is too hard, calcium residual build up could form on surfaces like pipes. But the original poster is correct. Washing soda (Sodium Carbonate) Na2CO3 can be substituted with Calcium Carbonate CaCO3, because all you want is the pH effects from the bicarbonate [CO3]-.