A couple of chemistry questions

[CC]

I've recently switched over to the BBB method and my pool water is looking pretty good. I do however have a couple of questions regarding TA and CYA for my pool.

What should my TA target be now that I've introduced Borates into the pool? My current TA test is showing about 60ppm which is at the low end of the spectrum but before I add any sodium bicarbonate I'd like to know what my target should be taking the borates into consideration.

The second question I have is regarding CYA levels in an indoor pool. My pool receives almost no direct sunlight and is testing at 0 ppm for CYA. Is there any reason to increase my CYA level?

My current chemistry numbers are...

Salt 3100 ppm
pH 7.4-7.6
Borates 50 ppm
CH 210 ppm
FC 5 ppm
TC 5 ppm
TA 60 ppm
CYA 0 ppm

As always, thank you for your input and guidance.

- Chad C

 

[dmanb2b]

If your PH is stable, there is no reason to adjust TA. CYA of 20-30 ppm is recommended, not for protection from sunlight but rather it is much easier to manage FC level at perhaps the 2-4ppm level, vs being more precise in the 0.2-1ppm range

 

[CC]

If your PH is stable, there is no reason to adjust TA. CYA of 20-30 ppm is recommended, not for protection from sunlight but rather it is much easier to manage FC level at perhaps the 2-4ppm level, vs being more precise in the 0.2-1ppm range

Thank you for the quick reply. The pH is fairly stable but it does tend to drift upwards requiring about 30-40 oz of muriatic acid per week to stay within the 7.4-7.6 range.

 

[George N]

The below is taken from Pool School

Second adjust CYA to between 70 and 80. The biggest mistake that many SWG owners make is NOT having enough CYA in the water! This can create a lot of problems like high acid demand, algae outbreaks, cloudy water, or early cell failure.

http://www.troublefreepool.com/pool-school/water_balance_saltwater_generator

 

[Butterfly]

The below is taken from Pool School

Second adjust CYA to between 70 and 80. The biggest mistake that many SWG owners make is NOT having enough CYA in the water! This can create a lot of problems like high acid demand, algae outbreaks, cloudy water, or early cell failure.

http://www.troublefreepool.com/pool-school/water_balance_saltwater_generator

Yes, but this is an indoor pool

To help avoid confusion, I'll move this thread to Chem 201.

 

[chem geek]

If you have no CYA in the water, then a high FC of 5 ppm has over 50 times the active chlorine level of what is recommended here on this forum! The chlorine will outgas from the water that much faster and will oxidize swimsuits, skin and hair that much faster as well and also produce disinfection by-products faster and in greater quantity (for nitrogen trichloride). So having 20-30 ppm CYA would be better and then keep your FC at around 2 ppm FC. You should find your chlorine demand lowered so that will let you lower your SWG on-time and that can help reduce the rate of pH rise.

The attached spa probably has aeration from jets and that will tend to drive up the pH, but keeping the TA lower should help. So I'd leave the TA where it is. Also, see what happens if you let the pH rise up more. It should slow down in its rise as the pH gets higher so you might be better off targeting 7.8 as your "goal" pH. If the pH continues to rise at a fast rate even as the pH gets higher, then the source of the rise is not carbon dioxide outgassing, but could be chlorine gas outgassing or something else unexplained. If your SWG is close to the first return in your pool, then the chlorine gas may not have enough time to dissolve in the water. You can try pointing your return downwards to see if that helps.

 

[George N]

Yes, but this is an indoor pool

To help avoid confusion, I'll move this thread to Chem 201.

My bad

Thanks for the education Butterfly

 

[CC]

If you have no CYA in the water, then a high FC of 5 ppm has over 50 times the active chlorine level of what is recommended here on this forum! The chlorine will outgas from the water that much faster and will oxidize swimsuits, skin and hair that much faster as well and also produce disinfection by-products faster and in greater quantity (for nitrogen trichloride). So having 20-30 ppm CYA would be better and then keep your FC at around 2 ppm FC. You should find your chlorine demand lowered so that will let you lower your SWG on-time and that can help reduce the rate of pH rise.

The attached spa probably has aeration from jets and that will tend to drive up the pH, but keeping the TA lower should help. So I'd leave the TA where it is. Also, see what happens if you let the pH rise up more. It should slow down in its rise as the pH gets higher so you might be better off targeting 7.8 as your "goal" pH. If the pH continues to rise at a fast rate even as the pH gets higher, then the source of the rise is not carbon dioxide outgassing, but could be chlorine gas outgassing or something else unexplained. If your SWG is close to the first return in your pool, then the chlorine gas may not have enough time to dissolve in the water. You can try pointing your return downwards to see if that helps.

Thanks for the suggestions CG. I'll leave the TA where it's at and tinker with the CYA level and SWGC settings a bit and see if I can bring the pH drift under control. I'll also let the pH come up a bit to see if it stabilizes around 7.8 as well. The water is looking good and the pH drift is pretty slow right now but if I could drive down the acid demand to 1/2 or 1/4 of what I'm using now that would be fantastic.