[mike31154]

That's strange. I've been using IO exclusively for years & my alk is always low. I find myself supplementing from time to time. Could be my test kit, but I've tried a few different brands of those & the results invariably come out low.

EDIT: I just remembered that a few years ago when starting my system (pre owned) the alk was quite high. I attribute this to the fact that I used treated tap water for the first year or so. Water source (Kalamalka Lake) is quite hard & once I switched to RODI, alk gradually dropped to the low side & has been that way ever since. If you're not using RODI, get some numbers/water report from your water supplier. City/municipal water reports will provide information on TDS levels and most organic & inorganic compounds that make their way to your tap. Alkalinity is usually in there somewhere.