To Slam or not to Slam...

[MrAl]

Hello Guys. Been a lurker here for a few months and learned A LOT. Did my first OCLT last night and ended up with a loss of 2ppm FC (8 hours total). Pool looks great, was suspecting a potential issue when I had to turn my SWG up past 95%, running pump for 19 hours with a break at night for the water to settle and dolphin to do a full clean. Pump schedule is as follows. I am running an electric heat pump set at 86.
0730-0800- 3000 rpm to stir after off cycle.
0800-1645- 20 GPMmin To make flow switches on heater and SWG
1645-1715- 3000 rpm to stir before and during water guru automated reading (reference only while I’m traveling for work)
1715-0300- 20 GPM for flow switches
0300-0730- pump off for debris to settle (2 hrs) and cleaning cycle (2.5 hrs)
Dolphin starts at 0500 for a 2.5 hr clean.
I am SW Florida and am in direct sunlight most of the day. CYA should be between 50 and 70. I’ve read the standard for an OCLT is a max loss of 1ppm. Does simply being over 1ppm automatically mean I have to slam? CC is less than 0.2. Yesterday I added 2lbs CYA to get from 50 to around 68 I’m expecting, and added 2 hours of hose water to account for evaporation (heater set at 86). Also yesterday we swam with the kids, do almost every day. Why I’m hesitant to slam if I don’t need to. Really looking forward to some responses as I’ve read some great threads here. Thanks!

 

[Texas Splash]

Welcome to TFP! Well, you do have many of the indicators that point to needing a SLAM. The OCLT, if performed correctly in hours of darkness and precise testing, is a good indicator of excessive organic activity, All the other items on their own not so much, but put it all together and it's looking like a SLAM Process is in your best interest. I would lower the pH to about 7.2 then use liquid chlorine/regular bleach to increase the FC to 28 since you just raised your CYA. If you're lucky, with clear water, maybe you caught this thing early to where the SLAM Process won't take too long. Just make sure to follow all the steps on that page and inspect and brush every inch of that pool for hiding algae. Remember, you can still swim in water up to SLAM level. Good luck!

 

[MrAl]

Hi Texas! Thanks for your input. It was a textbook OCLT with 2 samples taken each time before and after (same result). I forgot to mention, I get a fair amount of pollen and small debris from trees blown in the pool every day. Also have dogs and kids in the pool almost every day. Could my overnight loss of 2ppm simply be burning off what was introduced during the days use and not something breeding in the water? Just trying to make sure before I commit to slamming. My FC is always kept around 5-6. Planning on adding borates next week.

 

[MrAl]

So this is interesting... 2 days ago I did an OCLT and lost 2ppm over the course of 8 hours. Decided to SLAM. Took my FC to 28, per a 70 cya reading. Last test was at midnight last night, 32. At 0600 this morning I got 27. That’s .83ppm loss per hour with zero sunlight. And at normal FC levels I had only lost .25ppm/ hour. **scratching head**.

 

[Mdragger88]

Something’s brewing... keep at it! Also check all the algae hiding places ( light niches, ladder etc.) & scrub them.