Jandy Aquapure 1400 CYA levels

[wayner]

The manual for this SWCG recommends a level of 30-50. But on TFP the recommended level is 70-80 with an acceptable range of 60-90. Why does Jandy recommend such low CYA levels?

 

[ajw22]

Because Jandy simply parrots CYA levels recommended by the CDC in the last century. The government is slow to keep up with advancements in science.

 

[JamesW]

Why does Jandy recommend such low CYA levels?

Ask Jandy to explain their recommendations.

 

[wayner]

Are there peer-reviewed scientific studies that show that optimal level of CYA that I could use in asking them?

edit - In looking at the CDC website they seem to publish more info on what to do if someone poops or vomits in the pool, or overexposure to pool chemicals and don't seem to have recommendations on pool chemistry.

 

[jamesey]

What are the Correct CYA Levels for an Outdoor Pool?​

The recommended levels of CYA depend on the way the pool is chlorinated.

A CYA level of 30-50 is recommended when chlorinating with liquid chlorine. Pools in hot areas with intense sunlight can benefit from higher CYA levels to offset the degradation described below.

Salt Water chlorine Generation (SWG) pools seem to require a higher level of CYA, about 70-80 ppm, to operate efficiently. The theory is that the CYA is slow to "store" the chlorine as it is being generated so without enough CYA there is a build-up of chlorine that degrades the performance of the salt cell.[2]

An outdoor pool that is under a cage or cover does not need as much CYA as an outdoor pool in full sun.

CYA - Further Reading

www.troublefreepool.com

 

[jamesey]

Oops my bad. I misread your question about Jandy's recommendation. Disregard

 

[JoyfulNoise]

There are no peer reviewed studies because the pool chemical industry can’t be bothered with proving their claims. And they certainly aren’t going to waste money on R&D studies.

TFP’s recommended levels come from well over a decade of pool user experience with SWGs. It was found early on that with an SWG, one could maintain a lower FC/CYA ratio (~ 5%) but that maintaining a pool with low FC loss rate required higher CYA levels. The theory is that there is an additional protective effect from UV photolysis of chlorine by higher levels of CYA than what one would predict from standard first principles of chlorine/UV chemistry. Since SWGs produce FC at lower rates than simple manual chlorination with bleach, the higher CYA leads to greater protection of the FC from UV loss.

Like many others, my SWG runs at a very low output when the CYA is above 70ppm. This indicates that it is producing enough FC to overcome daily loss. But, if my CYA drops below 70ppm, I have a very measurable increase in FC loss rate that requires much greater output from my SWG. So there is definitely a strong concentration effect of CYA in my pool. Many others experience this.

Is there a peer reviewed chemistry paper proving this? No. But it is real.

 

[wayner]

Is there a peer reviewed chemistry paper proving this? No. But it is real.

I agree that it is real. But how do you change Jandy's mind. This is a bit of an exaggeration but if I send them an email saying "Some guy on the internet says that CYA should be twice what you recommend" what are they going to say? Likely a kinder version of "get stuffed".

This is almost a project that a pool owning chemistry professor could do as a side gig.

 

[ajw22]

But how do you change Jandy's mind.

Why do you feel you have to change Jandy's mind?

 

[JamesW]

Simply ask them to explain their recommendations.

Hi, you recommend X, can you please explain why?

 

[wayner]

Why do you feel you have to change Jandy's mind?

Or at least understand why they give these recommendations that appear to be wrong, and by a considerable margin.

 

[ajw22]

Or at least understand why they give these recommendations that appear to be wrong, and by a considerable margin.

Read...

Pool Water Chemistry

This thread presents my findings so far on pool water chemistry including the following: More Accurate Calcite Saturation Index (CSI) to replace Langelier Saturation Index (LSI) Calculation of ppm HOCl (disinfecting chlorine) at various levels of Total Free Chlorine (FC) and Cyanuric Acid (CYA)...

www.troublefreepool.com

You can choose to believe the science described or not.

 

[wayner]

Good stuff!