CYA and Chlorine

spoonman

Well-known member
Jun 16, 2016
338
Peoria, AZ
#1
Hi. I'm looking for an answer on testing chlorine relative to CYA.

Do the free chlorine tests compensate for the amount of CYA in the water? I understand there is a CYA/chlorine chart showing the required amount of chlorine at various CYA concentrations. However, most OTO test kits show an ideal chlorine range of around 1.5-2ppm. Why is this? If I run CYA at around 50 or 60, the ideal chlorine ppm would be off the chart if the OTO test doesn't compensate for CYA.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
41,197
Tucson, AZ
#2
There is no compensation in the tests. And that is why we recommend the FAS-DPD chlorine test as it can much more accurately test higher FC levels which are needed when CYA is in the water.
 

Jezza

LifeTime Supporter
TFP Guide
Jan 18, 2015
969
Bunbury, WA, Australia
#3
The manufacturers of testing equipment also don't generally factor in the FC/CYA ratio, which obviously requires higher levels of FC for the recommended CYA levels.
 

Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,300
NW Ohio
#4
If I run CYA at around 50 or 60, the ideal chlorine ppm would be off the chart if the OTO test doesn't compensate for CYA.
You know what I say when someone tells me something is "off the chart?"

"You need a better chart." FAS-DPD.
 

domct203

Bronze Supporter
LifeTime Supporter
TFP Guide
Jun 3, 2015
3,959
CT
#5
Hi. I'm looking for an answer on testing chlorine relative to CYA.

Do the free chlorine tests compensate for the amount of CYA in the water? I understand there is a CYA/chlorine chart showing the required amount of chlorine at various CYA concentrations. However, most OTO test kits show an ideal chlorine range of around 1.5-2ppm. Why is this? If I run CYA at around 50 or 60, the ideal chlorine ppm would be off the chart if the OTO test doesn't compensate for CYA.
This is exactly why we recommend using a FAS/DPD chlorine test, and mention that the OTO is really only good for confirming the presence of chlorine, not the actual amount with any accuracy.
 

Divin Dave

TFP Expert
LifeTime Supporter
Oct 2, 2013
5,192
Longview, Texas
#7
The pool industry in general doesn't recognize the FC/CYA relationship and that's why you see their FC recommendations of between 1 and 3.

Even though the effectiveness of the method, (backed up by solid science) of keeping a pool completely free of pathogens as well as algae, has been known since 1973, they have no interest in promoting the FC/CYA ratio that TFP does.

If they did recognize and promote it, then no one would need to buy all of the expensive chemicals which the pool stores and chemical makers sells.

The Pool Industry consists of businesses which exist to make as much money as they can. Providing the pool owner products that work for the long term is not in their best interest. They need you to repeatedly purchase their expensive products so they can stay in business. Whether or not whatever they can sell you is what you really need doesn't seem to be of any consequence to them.

It's pretty much as simple as that.


Hi. I'm looking for an answer on testing chlorine relative to CYA.

Do the free chlorine tests compensate for the amount of CYA in the water? I understand there is a CYA/chlorine chart showing the required amount of chlorine at various CYA concentrations. However, most OTO test kits show an ideal chlorine range of around 1.5-2ppm. Why is this? If I run CYA at around 50 or 60, the ideal chlorine ppm would be off the chart if the OTO test doesn't compensate for CYA.