Low CYA

Missy819

Member
May 30, 2022
23
Martinsville IN
Pool Size
17500
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)
I read that high amounts of FC will drop CYA. We finally dropped FC to 5 and turned on the SWG. Our CYA is at 40. Pool math is showing I need to add 3.5 lbs CYA to get it to 80. I’m nervous about add that much at once, not wanting to go over. What is the best way to do this?

Add all at once
Half now and test in a couple days
Add sock at a time, retest every cpl days.

I bought a 16oz bottle of CYA testing chemicals so I’m not concerned about testing more often.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
35,637
Sebring, Florida
I read that high amounts of FC will drop CYA.
Simply, not at all correct

Rather than go to 80 ppm, I would suggest 60 ppm. Perhaps, if chlorine consumption is too high, you could go to 80 in a few days.

I consider 80 ppm CYA as being in the "safe" zone but at the VERY top end of "safe"
 

pjt

Gold Supporter
Jan 7, 2012
806
The Woodlands, TX
Pool Size
21000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
I read that high amounts of FC will drop CYA
You didn't read that here.

Half now and test in a couple days
I would choose this option. CYA is very easy to add, but draining is the only practical way of lowering it. How much sun exposure does your pool have?
 

IceShadow

Gold Supporter
TFP Guide
Jun 8, 2019
4,188
Milwaukee, WI
Pool Size
20000
Surface
Vinyl
Chlorine
Liquid Chlorine
CYA has only a few ways to leave pool water.

- if there is a leak and you are refilling
- it does degrade naturally in water but slowly, 5ppm or so in a month
- there is a bacteria that can eat CYA and produce ammonia

One of these is the only explanation, short of testing error. The CYA test is hard to interpret and dependent on lighting, etc.
 
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