Calculating PPM by hand

[jblizzle]

I do not remember the details, but there was something done in PoolMath to adjust between the weight % of bleach (reported for low % bleach) and the trade % (which is what the higher concentrations use). I am guessing a regression model was applied in to match the relevant percentages that may deviate at unrealistic percentages.

I think often people get tied up in the details.
How accurately do you really know your pool volume?
How accurately to you really get 10 or 25ml in the vial?
How accurately to you really measure the volume of bleach added?
And of course there is error in the test itself anyway.

Too many sources of error to be concerned about it on a something that will change in an hour in your pool anyway.

 

[smackdab]

Bleach is labeled as weight percentage (ie: 8.25% sodium hypo) and liquid chlorine is labeled as trade percentage (ie: 10%, 12.5% sodium hypo). 10% weight and 10% trade are not the same figures. Trade percentage is easy to do by hand.

What you need to know is the trade percentage of the product to make things much simpler.
Bleach concentration per unit volume and other calculations

10% chlorinating liquid is 10% trade:
1 gallon of 10% trade will raise FC 10 ppm in 10,000 gallons

12.5% chlorinating liquid is 12.5% trade:
1 gallon of 12.5% trade will raise FC 12.5 ppm in 10,000 gallons

6% bleach is 6.17% trade:
1 gallon of 6.17% trade will raise FC 6.17 ppm in 10,000 gallons

8.25% bleach is 8.7% trade:
1 gallon of 8.78% trade will raise FC 8.78 ppm in 10,000 gallons

You can see where things are going from here.