Clorox shock

[Rickmart]

How much chlorox to shock a 20x40, 28,000 gal., in-ground? What are the advantages of chlorox over cal hypo?

[CarlD]

Chlorine is chlorine whether it comes from bleach, cal hypo, di-chlor, tri-chlor or salt water chlorine generation (SWCG). The AMOUNT of chlorine you need to shock your pool is based on two factors: the volume of your pool, but also the level of cyanuric acid (Stabilizer or CYA) in your water. For that level, check out the Best Guess table.

Cal-hypo adds calcium, which you don't need, but anything up to about 400ppm is no big deal. Bleach adds nothing but chlorine.
Di-chlor is slightly acidic but adds CYA--good if you need it, bad if your levels are already where you want it.
Tri-Chlor (usually as 3" tablets) is more acidic than Di-Chlor and also adds CYA--Again, good if your pH is a bit high and you need CYA, bad if you have low pH and high CYA.
SWCG adds nothing but chlorine.

Each gallon of 6% bleach will add 2.14 ppm of Free Chlorine to your pool. The newer 8.25% bleach will add almost 3ppm of FC per gallon to your pool. But how much you need depends on the CYA level.

[Rickmart]

Thank you. Very helpful. I'll have to check the CYA level..