CYA question for the experienced pro's

[mucoy]

This is my first summer with the pool. See signature for configuration. I understand the recommendation and rationale explained on these boards for keeping CYA around 80 for SWCG pool but I am wondering if that is still the recommendation when I am not having problems with CYA at 40 and already reasonably low SWCG run time. My CYA has been 40 since opening this spring and only running the SWG (intellichlor IC40) at 20% to keep FC between 2.0 and 3.0 even during this peak 100 degree plus week. The pump run time is around 12 hours. Sparkling water all season, no issues other than the chronic PH rise that is apparently typical with first year plaster and SWCG. Water balance stats are as follows:
TA 80.
CH 250
PH average 7.8 (acid controlled between 7.6 rising to 8.0 and treated again)
CYA 40
FC 1.8 this morning before pump was turned on. Generally, settles during day around 2.6 with pump running SWCG at 20%.

What are the expert thoughts on bringing up the CYA higher given the balance conditions I have now? It seems to me that I will just have to maintain higher FC levels to keep available sanitization the same, and if I do need to shock, spend more to achieve higher shock level. I ask, because CYA of 40 is counter to all the SWCG recommendations I have read, but it seems to be working for me without unecessary stress on the cell.

 

[duraleigh]

I am wondering if that is still the recommendation when I am not having problems with CYA at 40 and already reasonably low SWCG run time.

That's pretty easy, really. If it ain't broke......

(or as my friend says, "If it ain't broke, keep fixing it until it is!!" )

 

[wetwilly]

Great question! I won't attempt an answer because I'm no pro, but it is a question I've often wondered. Could the SWCG manufacturers have a conflict of interest on CYA levels knowing that higher CYA means more SWCG usage shortening the life of the cell?

 

[Poolschoolgrad]

The advantages of maintaining the recommended CYA concentration are increased cell life and shorter pump run times.
$10 for the cost of CYA seems like a bargain to be able to decrease the pump run time by up to 40% and to almost double the life of the cell.

The only advantage to a lower CYA concentration is "IF" you need to shock. If you maintain the proper chlorine/cya ratio, then you won't need to shock.

PSG

 

[JasonLion]

Raising the CYA level will allow the SWG to last almost twice as long as it will at the lower CYA level and will noticeably slow the PH drift, all assuming you have a Pentair automation system or Pentair acid feed system and can turn the SWG down to 10% or can shorten the pump run time significantly. If you can only adjust the SWG to 0% or 20% and can't lower the pump run time, adding more CYA won't help much (since you already have the SWG turned down as far as it will go).

Letting TA come down to around 60 will also slow, or perhaps eliminate, the PH drift.

wetwilly, raising the CYA level increases the life of the cell because the pool doesn't need as much chlorine, so the cell runs less often.

 

[mucoy]

Raising the CYA level will allow the SWG to last almost twice as long as it will at the lower CYA level and will noticeably slow the PH drift, all assuming you have a Pentair automation system or Pentair acid feed system and can turn the SWG down to 10% or can shorten the pump run time significantly. If you can only adjust the SWG to 0% or 20% and can't lower the pump run time, adding more CYA won't help much (since you already have the SWG turned down as far as it will go).

Letting TA come down to around 60 will also slow, or perhaps eliminate, the PH drift.

wetwilly, raising the CYA level increases the life of the cell because the pool doesn't need as much chlorine, so the cell runs less often.

Thanks JasonLion. I do not have any automation (yet) and it is not clear that I can lessen the pump run time that much as I prefer running at a lower speed on the VS pump to save electricity. Sounds like the "if it aint broke..." addage is at play here. I do agree that if I had automation and could turn down the output more it would further save cell life. I'm happily suprised that my chlorine output is as good as it is at CYA of 40. I don't get early morning sun, but pool is in full sun from late morning until 6:30 and it's still keeping up during this heat wave .

Thanks for the tip on further lowering TA to combat the pH rise. Are there any risk tradeoffs to running TA even lower at 60?

 

[wetwilly]

Jason,

Agreed, but increasing CYA well beyond the optimal level for a given SWGC would require more chlorine output, wouldn't it?

I was fighting too high CYA for years before I discovered this site and quit using tabs, "shock" and advice from the PS.

Thanks

 

[JasonLion]

Lowering TA down to 60 shouldn't cause any problems. You can go even lower if you have borates between 30 and 50, but without borates I would only go down to 60.

wetwilly, as CYA increases the amount of chlorine required continues to fall as long as there is no algae. However, at very high CYA levels it is easy to get a low level algae problem that isn't visually obvious. There is enough chlorine in the pool to prevent the algae from growing out of control, but not enough chlorine to ever kill all the algae. When that happens the amount of chlorine required goes up dramatically.

 

[Suziqzer]

I like you, was trying to run my swg at a lower cya level this year and found that as the temps finally began to rise this summer my swg was unable to keep up, even at night. I thought I'd try to keep it lower because I had to shock last summer do to my own error and wanted to avoid the high shock level if I failed again this year. I took it apart to clean it and found very minimal calcium deposits and it didn't change it's effectiveness... I was even running it at night in attempt to avoid the sun killing the chlorine as quickly as it was produced.

Early this week I broke down and added cya to get up to the 70 level and in just a matter of days my swg is having to be turned down. For me it makes a difference, especially now that the weather has heated the pool water. I thought my swg was failing... and it's only on it's second season.

I think it can vary by situation... water condition, temps, sun exposure, etc.

 

[JasonLion]

In nearly all cases running at the recommended CYA level (70 to 80) is better. But mucoy in particular already has the SWG turned down as low as it will go and is still getting enough chlorine even though it is the hot part of the summer.