CYA and salt chlorinators

[DanS]

I have read that cyanuric acid should be higher with salt chlorinators, but don't understand why, except that no new stabilizer is added with the chlorine made by the chlorinator. What cya level do you recommend for a salt water chlorinator? Will the cya actually burn off, or is it only lost due to backwashing, rain, etc? Can the chlorinator affect how long the cya lasts, or does it only affect it by not adding more cya like some forms of chlorine?

[JohnT]

The CYA doesn't go anywhere except when lost to splashout or backwashing or diluted by rain water. SWCGs just work better with the higher CYA level. Different manufacturers recommend different levels. Typically 50-80ppm.

[nater]

I had CYA levels over 120 my first year with a SWC due to puck usage prior to installing the SWC. This year I succesfully kept the pool algae free with CYA around 50-60. My output % on the SWC averaged 25% the first year, this year it was closer to 40%. Basically it worked a little harder to maintain FC this year, but I was able to keep FC lower and keep the pool clean. I see no advantage one way or the other.

[chem geek]

Basically it worked a little harder to maintain FC this year

That's the reason for the higher CYA. Though you needed to have a higher corresponding FC level, you were still able to set the output lower on your saltwater cell. So the net result was that your SWC would last longer if you ran your pool with higher CYA (because cell life is mostly based on the product of power output and the time it is on).

The main downside with running at higher CYA is IF you ever get an algae bloom for whatever reason (extended power outage or SWC failure without manual chlorine addition or algaecide usage as a backup), then it is much harder to battle at the higher CYA level due to the ridiculously high levels of chlorine required. Also, the higher FC level required at the higher CYA level makes the pH test less reliable (you also need a FAS-DPD test kit to measure the chlorine, but that's not a big deal and is what we recommend anyway).

If you have specific FC levels you were maintaining at your 120 ppm CYA and 25% SWC level vs. your 50-60 ppm CYA and 40% SWC level, I would appreciate your letting me know. Also, please let me know the brand and model of SWC or it's output rating (pounds chlorine per day, or grams per hour) and your pool size and how long you run your pump (and therefore the SWC time, if it were at 100%). I'm trying to model this extra CYA benefit effect so the more data points I have, the better (I already have some data from Janet's experience here as well as what Mark has measured via experiment here).

Richard