CYA rising during SLAM

Chris18692

New member
Aug 9, 2019
3
Charleston, SC
I’ve been working on clearing out my very green pool. I’ve been reading the site religiously to make sure I’m doing it right. My pool info is a 11,500 gal SWG pool, I cleared out all the debris, balanced all chemicals. PH to 7.2, CYA at 70, & been proceeding with the slam. About 4 days in its blue & cloudy. The issue I’m having is out of curiosity I checked the CYA & it’s around 90-100 now & my FC is still dropping about 5-6 each night I’ve done the OFCT. I’ve read test readings can be off during SLAMS so my questions are, is this something I need to worry about? & do I keep calculating liquid chlorine to add off of 70 or the raised (possibility false) level of CYA?

Thanks,
Chris
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
14,214
Bedford, TX
Chris,

CYA cannot go up unless you are add it... So, either your initial test was off or your last test is off, or you are using something with CYA in it...

High FC levels should not have any effect on the CYA..

That said, it is very hard to SLAM a pool with CYA over 40 ppm... Unless your water is incredibly expensive, you are going to spend more on Liquid Chlorine than you would if you drained 1/2 or 3/4's of your pool and started over with a reasonable CYA level..

Thanks,

Jim R.
 

Chris18692

New member
Aug 9, 2019
3
Charleston, SC
Thanks for the replies guys. As far as the CYA level, I was going by the CYA chart for SWCG pools that says 70 CYA with an FC slam target at 28. So am I incorrect with using those numbers? or should I be using a lower set?

Chris
 

DorsalSpine

Silver Supporter
Jul 8, 2013
480
Columbus, Ohio
That's the correct level for your CYA. It's just very hard to clear a pool at that level. It may be easier to lower the CYA with a water change, clear the water, and then bring the CYA level back up. The water change helps lower the CYA and clear the remaining water all at the same time.
 

Chris18692

New member
Aug 9, 2019
3
Charleston, SC
ah, ok I understand. I'll retest my CYA and confirm the level, I need to drain/fill to lower it anyway so it should be fine if I go ahead and lower it to 40 and continue the slam at those levels even though it's normally a SWCG pool?
I've had the salt cell turned off this whole time btw, and sorry for all the questions, this is all new to me so I'm trying to learn all I can.

Thanks,
Chris
 

aeh0603

Well-known member
Apr 6, 2016
237
San Diego, CA
The short answer is yes.

Having salt in the water does not impact a SLAM at all.
When your salt cell is off, treat the pool as if it is a non-SWG pool. This is because your SWG is turned off and you are dosing chlorine manually, the distinction concerns how you add chlorine, not how much salt is in the water.