What amount of CYA is best???

[mariner09]

I'm very close to completing the conversion from Bacquacil. How should I determine at what level is best to keep the CYA?

I have a 19200 gal IGV pool.

Fox Wall-Pak filter cartridges.

Most info indicates 30-50 ppm, but I've also seen the posts that say a higher level may not be bad and amount to less FC loss. I was thinking I would start with 30 and see what happens...

[Watermom]

I think starting at 30 is a good plan. You can always increase it if you decide you need to, but it is much more difficult to reduce it if you have more than you want. I typically run my cya around 40.

[waterbear]

How high to run you CYA depends in part on how much sunlight the pool receives. Running higher CYA levels can help prevent chlorine loss but you do need to run you FC a bit higher to compensate for the higher level of stabilzier. Start low and if there is too much loss of chlorine from the sun then raise your CYA a little at a time until you see an improvent in chlorine stability.

[NWMNMom]

Sitting at 35-40 most of the time here.

[ivyleager]

I must say that I usually have a CYA level in the 70-100 range due to prior puck and granular shock use. However, this year the CYA was at 30 on opening. I thought, great! Finally down. It's sitting at 50 now.

Well, I'm not liking it at all. My chlorine gets burned through almost daily, and I haven't had a huge pool party yet. I seem to be adding bleach every nite (all numbers are good, no CC's). When the CYA was in the 90's, the chlorine would hold for several days and I would only add bleach every other day or so. I am tempted to push the CYA up a bit more, but will see how pool performs this season with a lower CYA.

CaryB

[chem geek]

Cary,

The key is whether you are using more chlorine at the lower CYA levels with correspondingly adjusted FC levels according to Ben's Best Guess CYA chart. If you were maintaining a minimum of 5 ppm FC before (so obviously higher after you add chlorine so that it ends up at this level), then at the lower CYA level the FC would only be 3 ppm instead. In reality, the minimum chlorine amounts are more like the 0.03 column in this chart and the ratio of CYA to FC is what should remain constant.

So unless you maintained 3 times the FC level at a CYA of 90 than you did at 30, then the comparison isn't a fair one. We are looking into additional CYA benefits in a technical thread so any more detailed information you can provide regarding the FC level you were maintaining before at 70-100 ppm CYA and what you have tried to maintain now at 30-50 ppm CYA would be helpful to know. There may very well be a benefit to the higher CYA level beyond what has been traditionally said regarding diminishing returns.

Richard