1st SLAM - Follow Along with Me, Please

[glo76]

Been following this thread as it's similar to my own situation (my SLAM story is in another thread). We had a discussion about the consistency of readings from the FAS-DPD test. I think I'm comfortable that I'm doing the drop testing right, having done some comparison tests between the drop bottle and a 1ml syringe to dispense R-0871. Also used a 5ml syringe to get consistency in the size of my pool water sample. Having said that I still got one outlier result and a retest was needed. Also I put in 2 heaped spoons for my shock level ~24. By the way I'm on day 9 for what seemed like a very minor algae problem. I saw several 1.5ppm OCLTs through the mid-part of my SLAM. Probably the most frustrating part - so close, you think the next day it's going to be done tomorrow, and if it's not, it can get disheartening. But stick it out because you want to get it right. I'm on my second SLAM this year because I cut short last time and don't think I got all the algae, and in our weather it just grows back.

I'm switching to liquid chlorine because my inline chlorinator just isn't reliable enough, plus all the downsides to pucks. I expect to lose ~3 ppm/day at normal FC levels with my CYA ~60 (losing about 10-11 ppm/day during the SLAM). For my 16k gal pool 3ppm is 1/2 gallon of 10%/day. I'm planning to add a Stenner pump and tank and wire it to my Easytouch, just have to convince the wife of the value proposition.....

 

[cj3737]

Questions:
How long overnight should I wait for the OCLT tests?
I've normally done them well after sundown (10:00pm or later) and just before full sunrise (6:30am). There is some daylight outside but no direct sunlight on the pool (ranging from 7 - 8.5 hours overnight).

7-8.5 hours is fine...

 

[KatyTXPoolOwner]

glo76 - I followed along the thread of your SLAM and it appears that you and I have some very similar experiences.

Here we go for the day's events, starting with last night's last reading:

10:35 PM FC 24.5 & CC 0 (last night)
6:35 AM FC 23 & CC 0 (this morning)
7:50 AM Added 32 oz 10%
10:55 PM FC 13 & CC 0
11:00 PM Added 336 oz of 10% bleach
11:45 PM FC 24 & CC 0

Hoping for 23 or better tomorrow morning..........

 

[KatyTXPoolOwner]

I think a drum role might FINALLY be appropriate - and I have 1 more question:

FC 24 & CC 0 (11:45 last night)
FC 23 & CC .5 (6:35 this morning)

So it looks like I passed the OCLT - yeah! My concern is that I only waited slightly less than 7 hours. If somebody else smarter than me will confirm then I'll be happy!

Question:
Why did the CC creep up to .5? My last CC .5 reading was 4 days ago (Monday morning).

As always, thank you for all the help!

 

[Texas Splash]

Congrats on the OCLT! The time should be fine, and the CCs ... well... they can fluctuate based on what your water is processing and trying to oxidize at the time. We treat anything at 0.5 as zero. So you're good then! Now you have one SLAM under your belt and have learned a lot. Always test your FC daily to ensure it never drops below your target range, and never below the minimum required. Good work.

 

[KatyTXPoolOwner]

Hallelujah hot-diggity-dog! I passed OCLT and I learned a lot - from me running the OCLT and from the TFP community. Thank you.

From here, I let the chlorine drift back down to 7 (Target) and make sure it does not go below 5 (Minimum), per the Chlorine/CYA chart for my pool (CYA 60).

Questions:
When should I wait to test PH, TA, CYA, and CH again? Do I need to wait until FC is back to 5-7?

Yesterday, at 6:35am my FC was 23 and I added 32 oz of 10% right after that. FC should have jumped up a bit to 24 or so. At 10:55 last night my FC was 13, meaning I lost ~11ppm during the day. With that in mind, if I wake up each morning and my FC is 7, will I have to add enough chlorine (324 oz) every morning to go back up 11ppm to FC 18? That would mean spending around $65 weekly on chlorine (324oz daily X 7 days X $3.64 gallon). Is that correct?

 

[duraleigh]

I have not read this thread but that FC loss that you post...

At 10:55 last night my FC was 13, meaning I lost ~11 ppm during the day. With that in mind, if I wake up each morning and my FC is 7,

are not indicative of just having passed OCLT.......that loss is excessive.

With your FC of 5 or so, your daily loss should be about 2-3 ppm daily.

 

[glo76]

Dave - isn't it expected to lose a lot more FC during the day when doing a SLAM? Especially on a hot Texas summer day? Understand 2-3ppm/day when at normal FC levels (7 ppm for CYA 60) but wouldn't that same loss at shock level be more like 7-10 ppm? If I understand right, that CYA protects a percentage of FC.

Don't mean to hijack the thread just asking as a newbie. I was theoretically losing similar and occasionally even greater amounts through the day during my recent SLAM, but that's assuming the chlorine I was adding was at 10% strength and I don't think it was.

 

[KatyTXPoolOwner]

I have not read this thread but that FC loss that you post...are not indicative of just having passed OCLT.......that loss is excessive.

With your FC of 5 or so, your daily loss should be about 2-3 ppm daily.

My interpretation of this is that, even though the OCLT passed as of this morning (last night FC 24 CC .0; this morning FC 23 CC .5), since there was an 11 ppm loss yesterday during daylight hours (24 down to 13 over roughly 13-14 hours) on a hot summer day, I may still have water issues? Can you elaborate? Should I continue with SLAMming?

 

[ummgood]

I think when you are so high during a SLAM you lose more chlorine than you do at normal levels. I am seeing a ton of FC loss too and I think part of it is it is so insanely hot in Texas right now. I even have my SWG on and I am still having to add between 1 to 2 gallons a day even with the help of the SWG to keep at slam. Hopefully though when I am in normal range the SWG can be the sole producer of the chlorine. This just iterates in my mind that I have to keep testing daily during these hot days because you could lose so much chlorine fast that it could cause problems.

 

[duraleigh]

At 10:55 last night my FC was 13, meaning I lost ~11 ppm during the day. With that in mind, if I wake up each morning and my FC is 7,

Y'all are correct in that your chlorine loss is greater when your FC is much higher than normal. The hot weather will cause increased FC loss as well. I am going on the anecdotal evidence I have read over the years......not hard science, but I still believe that is excessive. A drop of 35% or so would have been maybe "barely OK" but from 24 to 13 is just too much. I would have expected about 4-5 ppm.

Yes, continue the SLAM, I think. That said, if your water is crystal clear, why don't you do another OCLT from you current FC level and see what you get tomorrow AM.

Pool Water chemistry is not an absolutely exact science so a second OCLT would be very reassuring.

 

[KatyTXPoolOwner]

Yesterday morning's reading:
6:35 am FC 23 & CC .5 (did not add any chlorine)

Last night's reading:
9:00 pm FC 10.5 & CC 1 (did not add any chlorine)
This morning's reading:
6:30 am FC 11.5 & CC 0 (did not add any chlorine)

Commentary:
So that comes out to a FC drop of 12.5 and a CC jump of .5 over a period of ~14.5 hours in the hot Texas sun yesterday (it was a full sunshine day all day and the high was 98 degrees and our pool gets a lot of sun).
This morning the FC actually jumped up 1ppm from last night, while CC dropped 1ppm.
The corresponding FC increase and CC decrease overnight had a neutral effect on the TC, which stayed the same at 11.5.

Questions:
1. Does yesterday's FC drop of 12.5 during the day mean anything?
2. Does yesterday's CC increase of .5 during the day mean anything?
3. Why would FC increase overnight?
4. Why would CC decrease overnight?
5. Does TC staying the same overnight mean anything?
6. Any other thoughts on questions I did not ask?

I'm cautiously optimistic that my SLAM is complete but will defer final judgement to the much smarter TFP community (although, I've certainly learned a lot about pool chemistry over the last week!).

Thank you again!

 

[duraleigh]

FC actually jumped up 1ppm from last night, while CC dropped 1ppm.

Chlorine can only increase if you add chlorine.....the increase is not plausible. Your testing will get more accurate with practice and probably had something to do with that excessive loss yesterday.

For now, I would (with caution) say your SLAM is complete so you have met the criteria...

1. Your pool water is sparkling and there is no visible algae (dead or alive)
2. Your CC's are .5ppm or less
3. You can hold your FC overnight without losing more than 1ppm.

Questions:
1. Hard to say.....not sure it was really that much drop.
2. No
3. It cannot
4. CC's are transient and can increase and decrease independent of FC
5. No

 

[KatyTXPoolOwner]

Thank you, Dave, for your insight.

 

[KatyTXPoolOwner]

SLAM finally complete - OCLT holding up.

Only lost 2 PPM FC yesterday during 13 hours of sunny and hot weather.

Went ahead and gave my 2 year old Quad DE cartridges an acid bath over night (6 parts water, 1 part muriatic acid) for their 1st bath. Reassembled and recharged filter this morning and dropped my pressure from 10 down to 6. Nice improvement! Pool cleaner is back in the water after a week long vacation sitting out of the pool, including a couple days of soaking it in a FC 10 solution. Back to work for the cleaner!

Thank you again TFP community for the guidance - much appreciated!