Spiking FC

[Demegrad9]

For 2,500 gallons getting from 50 to 100ppm total alkalinity only takes 29oz Baking Soda

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Why are you shooting for 100ppm total alkalinity anyway. Can you share all your most recent test results?

 

[Kit]

Oops! My bad! For some reason the water volume in the Pool Math calculator was 10,000 gallons. I thought something was wrong. The volume might have reverted to default when I migrated the data from my old computer to the new one. Thanks for the correction!

 

[Demegrad9]

Just a reminder though, 80ppm-120ppm TA has been the recommended level classically, but people here have found that pH is much more stable for our pools around 60ppm-80ppm TA. So I don't know exactly your experience or history with your spa, but I just hope your not shooting for 100ppm TA just to be in some old recommended range.

The important thing to remember is that the RIGHT total alkalinity is where pH is relatively stable. If pH tends to rise over time in your spa then TA is too high. If pH tends to decrease over time then TA is too low.

 

[mknauss]

I would not target that high of TA. Use PoolMath and get it to no more than 60. Then see how the pH reacts.

Not sure what reaction compounds come from Sodium thiosulfate. I would be skeptical of the 'sulfate' as they are bad news for metals (aka SWCG) and plaster.

I would not use any more of that.

Take care.

 

[Kit]

Again, thank you for the info. One question though: Is the hydrogen peroxide that is commonly available of sufficient strength compared to the same product made specifically for pool application?

 

[mknauss]

You do have to use quite a bit of it. But your volume is small and you really should never need it. If you search the forum there is a calculation available based on % strength of the hydrogen peroxide.

Your pool is safe to swim in with FC up to shock level based on your CYA. You have not shared with us what your CYA is.

See Pool School - Chlorine / CYA Chart

 

[Kit]

Cya = 40.

 

[mknauss]

So if you look at the FC/CYA chart linked above, your shock level FC is 16. So no need to reduce FC unless above that.

Take care.

 

[Kit]

Thank you, Marty.

 

[cfherrman]

I just saw a bunch of posts about hydrogen peroxide, basically the store quarts are 3% and unless you get the pool version, 30%, at a discount the store stuff is cheaper

 

[Kit]

I just saw a bunch of posts about hydrogen peroxide, basically the store quarts are 3% and unless you get the pool version, 30%, at a discount the store stuff is cheaper

Thanks for the info. Hopefully I can avoid the spiking FC in the future.