Increasing Drinking Water pH

We are ​planning to use ​sodium ​carbonate (​Na2CO3) or ​sodium ​hydroxide (NaOH)​ in few ​drinking water ​applications to ​raise the pH: ​

• Na2CO3 to ​raise pH from 7.​ 1 to 8 ​
• NaOH to raise ​pH from 5 to 7. ​5

Do we need to ​use the food ​grade  ​sodium ​carbonate and ​sodium ​hydroxide? What ​are the ​possible ​dangers of not ​using the food ​grade  ​Na2CO3 and ​ NaOH?  ​

Is there a ​cheaper method ​of increasing ​the drinking ​water pH if the ​food grade ​ Na2CO3 ​and  NaOH ​need to be used?​