CYA Levels for Indoor Pool

[dmccarthy]

I understand the TFP recommends a CYA level between 20-30ppm for an indoor pool and the reason would be different than protecting chlorine levels from UV rays.. Mine is commercial indoor pool used for therapy.
Temp: 94 degrees
Sanitizer: liquid chlorine via Hayward controller direct injection
pH control: Carbon Dioxide injection (hayward controller)
Inline UV lamp that runs 12 hours/day, pool pump runs 24/7 as required by state.
High-rate sand filter.

*Fly in the ointment...my state (Massachusetts) states we are supposed to have 0 ppm of CYA in a commercial indoor pool. I have not put any in, however I am curious as to the reason I would add it. I can't find if the state has changed their rules. I would assume my UV lamp is chewing up some of the chlorine (as well as the high temp), but I still do not go through more than about a gallon of sodium hypochlorite/day.
Thanks,
Darin

 

[Sunnydaze]

I understand the TFP recommends a CYA level between 20-30ppm for an indoor pool and the reason would be different than protecting chlorine levels from UV rays.. Mine is commercial indoor pool used for therapy.
Temp: 94 degrees
Sanitizer: liquid chlorine via Hayward controller direct injection
pH control: Carbon Dioxide injection (hayward controller)
Inline UV lamp that runs 12 hours/day, pool pump runs 24/7 as required by state.
High-rate sand filter.

*Fly in the ointment...my state (Massachusetts) states we are supposed to have 0 ppm of CYA in a commercial indoor pool. I have not put any in, however I am curious as to the reason I would add it. I can't find if the state has changed their rules. I would assume my UV lamp is chewing up some of the chlorine (as well as the high temp), but I still do not go through more than about a gallon of sodium hypochlorite/day.
Thanks,
Darin

It's recommended to provide a buffering effect and reduce the harshness of the chlorine. I do believe the recommendation is for residential pools which are not under government regulation.

 

[Newdude]

*Fly in the ointment...my state (Massachusetts) states we are supposed to have 0 ppm of CYA in a commercial indoor pool.

Many places have such regs and while some are coming around to it, most still outright ban CYA

I have not put any in, however I am curious as to the reason I would add it

With an indoor pool it’s purely for Swimmer comfort. The CYA buffers some of the chlorine and makes it less harsh on the skin.

*edit. Kevin beat me by seconds. Well done Sir !!

*2nd edit. But I beat Marty by seconds and I’ll TAKE that win. Woo woo.

 

[mknauss]

CYA is used to protect chlorine from UV, and also for swimmer comfort. The following chart shows the Active Chlorine levels at different measure FC levels, with CYA amounts.

As you can see. The HOCl (active chlorine), with 0 CYA and 1 ppm FC, is about 0.4 ppm. At 30 ppm CYA you need about 20 ppm FC to reach that. So some CYA in the water, with a minimum FC of 3 ppm, is much more pleasant than 0 CYA, and 1 ppm FC.

 

[HermanTX]

CYA is used to protect chlorine from UV, and also for swimmer comfort. The following chart shows the Active Chlorine levels at different measure FC levels, with CYA amounts.
View attachment 367217
As you can see. The HOCl (active chlorine), with 0 CYA and 1 ppm FC, is about 0.4 ppm. At 30 ppm CYA you need about 20 ppm FC to reach that. So some CYA in the water, with a minimum FC of 3 ppm, is much more pleasant than 0 CYA, and 1 ppm FC.

Just curious - was this chart used to develop the CYA-FC chart used by TFP? Is this how the 7.5% minimum was derived for pools using LC?

 

[mknauss]

Just curious - was this chart used to develop the CYA-FC chart used by TFP? Is this how the 7.5% minimum was derived for pools using LC?

Essentially. Read Pool Water Chemistry