Arg-g-gh! 1/2 tsp in 1 gallon?? You're going to make me work hard. I'm used to figuring doses in 10,000 gallons of water or even 120,000 gallons. But working with 1/2 tsp in 1 gallon? Sheesh.

Ok. Better do it here so someone can check my math.

1 US teaspoon = 4.92892159 milliliters
1 US gallon = 3,785.41178 milliliters or 3,875 gm

1/2 tsp = 2.46 ml = 2.46 gm/H20
at 6% bleach that's approximately 0.148 gm Cl2 equiv

so your dose was
(0.148 / 3 875) * 1 000 000 = 38.1935484

or 38 ppm chlorine.

Yep, if my math and your testing is correct, you've got a lot of chlorine demand there.

I'd recommend using 4 gallon (~10ppm) doses in the evening, and continuing till you hold a residual.

Watch your pH during this, and add borax a box at at time, to keep it above 7.6


Have fun!

PoolDoc