SLAM level held for 12 hrs during day yesterday w/no added bleach, but OCLT -2ppm!

[Lynnster52]

Attended Pool School over the last week & using PoolMath & newly acquired FAS/DPD chlorine test kit.
Performed 1st SLAM yesterday but failed OCLT. Can there be a "but" on the but?

Yesterday there was no sun with air temp in the 50's. TFP Chart called for 10ppm SLAM & 1 gal of 8.2% bleach. SLAMmed early am. 20 mins later FC:11 ppm. Two hours later (& all thru the day) FC:12. (tri-chlor auto feeder was set to lowest setting during SLAM so this might be reason FC went to 12ppm, not 10ppm) Turned off feeder at 10 pm, did final test at 11 pm and FC was 12ppm. At 6:30 am today, FC:10 ppm so failed OCLT as lost 2 ppm overnite.

TROUBLEMAKERS: Pool is 25 yards from school ball field (all dirt infield) in constant use (recess & midget league 7 days/wk) And our trees are currently dumping pollen, so we are not sure we have dirt/pollen combo or algae, but see small brown piles on liner floor & brown along floor seams.

When we brushed, there were clouds. If algae, wouldn't the chlorine level drop considerably, requiring more bleach, even with auto feeder on at lowest during the SLAM? Today brown spots & brown along the seams are back... so with failed OCLT, I guess time to SLAM again...

Should I assume it's mustard algae & SLAM for that? Or just keep FC at 10ppm SLAM level, brush/test often (& leave auto-feeder off) & see how testing goes today, with another OCLT tonite? Tks!

Current readings:
water temp: 66º
FC: 10
CC: 0
PH - not testing as FC too high, but was 7.6 when SLAMmed yesterday
TA 80
CYA: <30 (Assumed approx 25-28 as dot disappears soon after 30 level) Two bags of Di-Chlor added 5 days ago & tri-chlor auto-feeder both add CYA. Pool opened in the last week & I read that CYA can take time to show up, so I don't want to add CYA just yet IF it's ok to wait a bit on it.

 

[Texas Splash]

We all get pollen, dust, and local junk blowing onto the water and it sinks to he floor or gets caught in seams. That's okay. Just makes things look messy, but shouldn't really disturb your FC results too badly. But if you have algae, generally you'll know it because the FC will rapidly. So let's make sure we understand a few things. For example, we know your CYA is slightly low, so that may be a good reason to use tablets right? However also remember that those tabs, while packed with stabilizer, are also acidic, so they can influence your pH and TA and try to drive them down. So be mindful of that. For a SLAM, it's important to realize it's not a one-time punch of chlorine, or even 1-2 days. A SLAM can take a few days depending on the amount of algae in the water. Algae is not always green or thick, sometimes it's just hazy or can even appear somewhat clear.

I'm not so sure what you are seeing is algae - yet. Since your first OCLT seemed to be a bit unpredictable, I would recommend doing another one this evening. This time however, add your last amount of bleach about 30 min before taking your final bedtime FC reading. There should be no other source of chlorine influencing the OCLT, so remove or close-off the tablets completely. After about 30 min, the bleach should be mixed well so you can take test #1 before bed. In the morning, if the pump was off, make sure to run it for about 30 min before grabbing the morning water sample. It needs to mix well. Get the sample before the sun hits the water, and grab it from the same location as the night before.

I would start there and see what you come back with tomorrow.

 

[Lynnster52]

....Since your first OCLT seemed to be a bit unpredictable, I would recommend doing another one this evening. This time however, add your last amount of bleach about 30 min before taking your final bedtime FC reading. There should be no other source of chlorine influencing the OCLT, so remove or close-off the tablets completely. After about 30 min, the bleach should be mixed well so you can take test #1 before bed. In the morning, if the pump was off, make sure to run it for about 30 min before grabbing the morning water sample. It needs to mix well. Get the sample before the sun hits the water, and grab it from the same location as the night before.

I would start there and see what you come back with tomorrow.

THANK YOU! Will do!
Pool had hardly any debris or "brown seams" this am. Water still crystal clear.
Forgot to clean cartridge so will do today. We did turn off auto-feeder last nite & it will remain off til tomorrow am after OCLT testing is over.
Keeping FC at 10 today & brushing.
Having auto-feeder on (even at lowest setting) during the SLAM yesterday was probably bad idea, but but hubby insisted as has pucks & he refused to take then out! But he agreed to turn feeder off last nite (told him we had to for the OCLT!) So no worries now as auto-feeder is off until after SLAM & we pass 3 points of OCLT test - hopefully tomorrow am!
p.s. pump is running 24/7