Based on discussion I found in the archives from this list, I picked
up a jug of HTH-brand Ph Minus at Wal-Mart today for about $8. Ph
Plus was on sale for $6, but I noticed that it’s active ingredient is
Sodium Carbonate (Ph Minus ingredient = Sodium Bisulfate). I also
noticed that in both cases it claims only a 92% portion of the active
ingredient and 8% “inert.” I’m a little skeptical that the 8% may be
significant when used as a pickle (the swimming pools surely don’t
care). If Sparex is worse than 92% NaHSO4, it really must be dirty.