Min CYA for SWG

[fanis.merk]

Maybe I am hallucinating but it seems the min CYA requirement for SWG on

Chlorine CYA Calculator

has increased since last year. The minimum acceptable went up from 30 to 60. What is the reason for this? Have there been some new developments or change in methodology?

Thanks

 

[JoyfulNoise]

Minimum CYA for SWGs has always be 70ppm for a very long time. SWGs add chlorine very slowly to water and most people with them find that their FC loss rate greatly increases when the CYA level is below 70.

30ppm CYA is the minimum for manually chlorinated pool (liquid chlorine).

 

[fanis.merk]

Minimum CYA for SWGs has always be 70ppm for a very long time. SWGs add chlorine very slowly to water and most people with them find that their FC loss rate greatly increases when the CYA level is below 70.

30ppm CYA is the minimum for manually chlorinated pool (liquid chlorine).

I am pretty sure things changed in time because if you see this article

CYA Chlorine Relationship - Further Reading

it is warning non to exceed 70-80 CYA. Now in the new chart we are talking about even 90 CYA levels. And in some pages there is a star next to 60

FC vs CYA chart location

and in some other pages not, which is an evidence to changes in time. Now if minimum is 60 (or 70) and not to exceed 70-80, the range is confusingly tight I would say.

 

[Texas Splash]

I've been here for over 11 years and the numbers have been relatively constant. That Wiki article does its best to provide the background to the FC-CYA relationship and describe various comparisons between TFP and the generic pool industry recommendations. But from that article you quoted:

"High CYA levels are often called over-stabilization by Pool Stores. What is a high CYA level depends on the way you chlorinate your pool and your local environment. In general pools chlorinated with tablets or liquid chlorine should have CYA up to 40ppm. Pools chlorinated using a SWG can have CYA up to 70-80ppm."

We have been referring to these two charts for years:

 

[Newdude]

We did adjust the SWG chart last winter to have a target range. Trying to 'maintain a 5' was a fools errand on the original chart. While most SWG pools swing less than LC pools, they do still swing.

The old target is the new low target.

 

[Newdude]

and in some other pages not, which is an evidence to changes in time.

Here is the original #s from the 'old school chart', which this is a mirror of.



I did find 60 listed as ok if checking the FC/CYA link and clicking 'show full chart' on the calculator.




It doesn't agree due to an oversight. Let's notify @Leebo to add one more thing to the mile long honey do list.

 

[Leebo]

Back in 2019 we updated the levels as low as 60 as recommended. Over the years however there’s been an error in the charts that showed 60 as not recommended which was fixed.