Unfortunately, both the chemistry AND the terminology for pool pH and alkalinity is confusing. "Alkalinity" is sometimes used to mean "the pH is alkaline or above 7.0". But with respect to water chemistry, when the term "alkalinity" is used technically, it does NOT refer to water pH levels, but rather to the water's resistance to pH *change*.
Thus, water can be "acidic" -- low in pH -- and yet have "high alkalinity" -- high resistance to pH change.
Where it gets even more confusing is that most POOL alkalinity is based on carbonates, which tend to be active when the pH is higher and the water is "basic" or even "alkaline". So, while "alkalinity" in general is not necessarily associated with high, carbonate alkalinity is!
Let me make it simple. Taylor's book is the worst thing about the K2006, and like many other pool guides, creates the false impression that pool water chemistry can be managed like a recipe: 2 eggs, 1 cup of flour, 1/2 cup of milk -- mix with 1/4 cup of butter and pour into a hot greased pan for pancakes.
The problem is, recipes are for EVENTS, not for PROCESSES. Pool management is a process, not an event. For this reason, it's much, much more practical to follow the "test, adjust some, re-test, and adjust some more" PROCESS MANAGEMENT approach, then it is to follow the "test, calculate exact dose, dump and hope for the best" EVENT or RECIPE approach.
So . . . do this:
1. Lower your pH to 7.4 or so. You can try a quart of muriatic -- just keep dosing till you get there.
2. Then, add a dose of baking soda. If you want to start with 2 lbs, that's fine.
3. Then CONTINUE adding acid till your pH is OK, AND
4. CONTINUE adding baking soda till your Alk is high enough.
Get your pH in range ASAP. But otherwise, no hurry --if you get it all balanced in 2 weeks, that's perfectly fine . . . because you are managing a PROCESS, not an EVENT, and because plaster damage (if any) is very slow when the pH is between 7.2 and 7.8.
Realistically, you are probably looking at gallons of muriatic acid, and way more than 2 lbs of baking soda . . . but that's OK. READ the muriatic acid guide linked in my signature; get your baking soda at Sams Club or Walmart. (At both locations, it's less than $0.60/lb as "baking soda" but more than $1.50 as "alkalinity increaser"!)