High water source alk

[purge43]

If the water a person uses to make ro/di has a high reading from a fresh water test kit, will the resulting artificial sea water also have a high alk? Will 8+10=18?

 

[disc1]

The RODI filter will remove all of the alkalinity. The RODI water should have an alkalinity of zero. If it doesn't then there's a problem with your filter.

But yes, alkalinity is sort of additive. If you mix 2 gallons of water with an alk of 8 with 8 gallons of water with an alk of 10 then you will get ((2*8) + (8*10)) / 10 == 9.6 for the alkalinity of the mix.