High CYA High Target FC

[Jcangelo]

My CYA has been tracking high. It started at 145 a month ago and I am now down to 118 through dilution with fresh water. Pool Math is recommending target FC from 9-15 and I imagine that it is because my CYA is so high, however, the target has not dropped as my CYA has dropped. As of today, my FC is sitting at 6.0 and I am questioning if I need to continue to raise my FC to the 9-15 range every week or if a lower FC is acceptable.

The reason my CYA was so high is because the prior homeowner had a service that was using tabs. Since I took over the maintenance in November, i have been using 10% liquid chlorine exclusively. My full slate of readings as of today are FC 6, PH 8, TA 81, CYA 118, phosphates 485.

 

[Bperry]

My CYA has been tracking high. It started at 145 a month ago and I am now down to 118 through dilution with fresh water. Pool Math is recommending target FC from 9-15 and I imagine that it is because my CYA is so high, however, the target has not dropped as my CYA has dropped. As of today, my FC is sitting at 6.0 and I am questioning if I need to continue to raise my FC to the 9-15 range every week or if a lower FC is acceptable.

The reason my CYA was so high is because the prior homeowner had a service that was using tabs. Since I took over the maintenance in November, i have been using 10% liquid chlorine exclusively. My full slate of readings as of today are FC 6, PH 8, TA 81, CYA 118, phosphates 485.

If those numbers came from a pool store then the first bit of advice would be to toss them and not do anything based on them. They are really universally terrible at water testing. They are especially bad at testing CYA.

TFP only recommends trusting results from a Taylor K2006C or a TF-100 (tftestkits.net).

But yes if your CYA really is over 100ppm, then your chlorine does need to be that high as you’ll likely start growing algae if it isn’t. But I doubt your CYA test result.

 

[Mdragger88]

.... "Min FC" is 7.5% of the CYA level
.... "Target FC" is 11.5% of the CYA level
.... "Yel/Mstrd Min" is 15% of the CYA level
.... "Shock FC" is 40% of the CYA level
.... "Yel/MstrdShock" is 60% of the CYA level.

Chlorine/CYA Chart

EDIT: You will find a simplified and standardized version of this chart at Pool School, Chlorine / CYA Chart. Chlorine/CYA Chart by Chemgeek FC = Free Chlorine in parts-per-million (ppm) CYA = Cyanuric Acid in parts-per-million (ppm) CYA ........... Min FC3 ..... Target FC ...... Yel/Mstrd...

www.troublefreepool.com

If your test results are correct This means-
Your minimum is 9ppm
Your target is 13.8ppm
Shock/SLAM Process level is 48ppm
Please understand that Failure to maintain adequate maintenance fc above minimum for your cya will result in the need to achieve shock/slam level fc which is impractical at your cya level.
It would behoove you to exchange most of your water sooner than later to get down to a reasonable cya level. *But first you need reliable test results from a Taylor k2006 or tf100/pro to determine just how much.
Winter is a good time to accomplish this.
Here’s the details so you can prepare yourself

Draining - Further Reading

www.google.com

 

[proavia]

Pool store test results are marginal at best.
No one cares about your pool more than you do.
Get one of the recommended test kits and test the pool water yourself.
Test Kits Compared
The TF-Pro (with stirring device) or the TF-100 (plus stirring device) are the best value for the residential pool owner. These two kits contain more of the reagents we use as residential pool owners.

If your CYA is really 118, you need to drain and refill 50% to 60% of your pool volume to get CYA down in the 50 to 60 range.

While waiting for your test kit to arrive, have a read thru Pool Care Basics and maybe have a look thru some of the Trouble Free Pool videos on YouTube.
Here's one to get you started: