Chlorine concentration and Pool Math calculation

gorocket1981

Well-known member
Jun 8, 2018
127
Montreal, Canada
On the liquid chlorine gallon that I buy, there is 2 concentration written:
Sodium Hypochlorite: 10.8%
Available chlorine content: 10.3%

Which one is the concentration to use when doing calculations, like in Pool Math app? Until now, I used the lowest to be safe, but which one is the good one?

Also, I have a weird issue with Pool Math. It is the iOS version.
I go in Effect of Adding. My Pool Volume is set to 43250 Liters.
I select Bleach. I enter 10.3 in Percentage. In amount, I enter 1 Liters.
Calculation is done result is Raise FC by 2.9 and SALT by 4.8

If I change the Bleach Percentage to 12%, the values does not change. Even if I put 20%, the value is the same than for 10.3. For a LC of 12% I would expect the FC to be higher.
Unless it is only on my side, I think that there is an issue with the Effects of Adding. I played with it and when I change the Percentage, values are not always changing.

With that said, basic question, it the result of Raise FC by 2.9 and SALT by 4.8 correct if I add 1 Liter of 10.3% LC ? Is it accurate?
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,260
Tucson, AZ
2.9 FC and 4.8 salt is actually how much 12.5% bleach will add to your pool.

Generally the strengths that are common to use for bleach are 6, 8.5, 10, 12.5%
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,260
Tucson, AZ
I do not have the app available to me right now.
I just used the old PoolMath webpage (link at the bottom of the page)

10% would be adding 2.3ppm FC and 3.8ppm salt to your pool
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,396
Laughlin, NV
The app will only recognize the normal Bleach concentrations, 6, 8.25, 10, and 12.5. If you put in a value other than those, it rounds up to the next expected level.

@Leebo -- something to have for the next App upgrade.
 

gorocket1981

Well-known member
Jun 8, 2018
127
Montreal, Canada
Ho ok! Good to know.

A suggestion. I think that it would be better for the app to use the value entered in the box. It would be more flexible and would accommodate more to what product is purchased. It would then be more accurate.

In the meantime, is doing a Third Rule calculation accurate? To have the results for 10.3% and 12%.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,396
Laughlin, NV
You can interpolate if you like, but to be honest, I would select one of the known bleach concentrations and use that. For your 10.8%, use 10%. Better to overadd bleach a bit than under add.