Time to SLAM Again and Why Do I Lose CYA?

Red

LifeTime Supporter
Sep 11, 2010
81
Orange County, CA
A few weeks after I successfully completed a SLAM Process, it looks like it's time to do one again. I've been needing to add more chlorine recently and just did an Overnight Chlorine Loss Test and it failed :(.

I understand there's a constant battle going on between the chlorine molecules and other uninvited organisms that want to come and have their own party in my pool. I'm wondering why the chlorine seems to do just fine sometimes and other times it gets overwhelmed. What kinds of things get into the pool water that overwhelm the chlorine? Do they tend to come from nature or people in the pool? Right now, my water temperature averages between 82-86F/28-30C (no heater). I'm sure the warmer water helps these organisms win the battle. I believe SLAM is effective because it just overwhelms the bad stuff and kills it before it can reproduce, right? My anguish now is that it's probably the 3rd time this swim season I'm having to do a SLAM, and it's not that long after my previous SLAM. Is it just bad luck with Mother Nature or indicative of something else?

My other complication is that for years it's been difficult for me to maintain my CYA level. I add conditioner and the CYA doesn't seem to stay long. TFP people have said the only way to lose CYA is through water loss, but that doesn't seem to be my experience. My CH sure likes to build up until I drain/refill, but the CYA doesn't. I also did an evaporation test ~2 years ago and that didn't show any loss beyond evaporation. For example, maybe 4-5 weeks ago, CYA was at 60. I added CYA ~2 weeks ago. Yesterday I tested and it was at 50.

The pool does get used several days a week, but typically it's 2-4 people and not a great deal of splashing or waves. There are some other occasional, bigger events, but nothing recent.
 
Last edited:

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,396
Laughlin, NV
CYA does degrade at a slow rate during the summer, primarily from elevated water temperatures.

Having to follow multiple SLAM Process implies you are not completing one all the way. Or you are not maintaining your FC using the FC/CYA Chart for your CYA. Aim for a FC just above the target range. With a 70 ppm CYA, which you should have for your SWCG, aim for 7 ppm FC.

I also suggest getting the PoolMath app and using it to store your test results over time. It helps to see the trends and adjust your SWCG, etc, to match your FC demands.
 

Red

LifeTime Supporter
Sep 11, 2010
81
Orange County, CA
Having to follow multiple SLAM Process implies you are not completing one all the way. Or you are not maintaining your FC using the FC/CYA Chart for your CYA. Aim for a FC just above the target range. With a 70 ppm CYA, which you should have for your SWCG, aim for 7 ppm FC.
I appreciate your idea here of targeting 7 FC. I've probably been more around 5-6. I'll try aiming higher after I finish my next SLAM.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
15,796
Tucson, AZ
Have you checked your pool for a leak? Given where you live, you should not need to frequently adjust CYA unless you’re getting a lot of rain-overflow.