Starting from Scratch

[Watermom]

Trichlor is acidic so if you decide to use it for awhile, it will drop the pH for you. The only drawback to using the trichlor is that until you have some CYA in there, you'll have to be adding chlorine often. So, you might want to go ahead and add your 4 lbs. of granular CYA which should add about 25ppm of CYA, to get some stabilizer in there more quickly. Then, use your trichlor for awhile. Once your CYA is 40-50, you'll want to switch to an unstabilized form of chlorine like bleach. Alternately, if you don't mind having to add chlorine so often (as in several times per day at first), then you can just use trichlor and not add the granular CYA. Either of these options will work just fine.

(Don't forget to watch your pH while using trichlor.)