SLAM & OCLT questions

[Gollie]

TL;DR: (skip down to numbered questions)

This is my first season as a pool owner and my absolute worst fear has just happened - algae.

I have spent all summer trying to get all of my chemicals perfectly balanced at the same time and I FINALLY achieved it about a week and a half ago...and then yesterday I discovered some algae collecting in the middle of the pool. I should have known it was coming bc FC was getting gobbled up more rapidly than usual. I even did regular maintenance level shock treatments* night before last and the night before that. Last night I did a double shock treatment** and I can still see some green in the middle.

I should also note that when I say "some green" I mean the vast majority (95-98% ish) of the pool is crystal clear; we're nowhere near a full bloom (yet).

My plan is to brush and vac to waste after work and then double shock it, see where I'm at tomorrow, and repeat if necessary. In other words, SLAM is the plan. I read the TFP SLAM article (and  many others) but I still have some questions.

1. If I brush before vac, which is what it says to do, aren't I going to stir up the algae that's currently collected in the center of the pool, thus causing it to float around instead of resting on the bottom where I can get it with the vac?

2. I also read the OCLT article and it says to wait at least 30 minutes after last chem addition of the day, but how can that possibly give an accurate FC reading? Based on my calculations, it takes roughly three hours for all of the water in my pool to complete a filtration cycle. Testing only 30 min after adding a huge dose of shock doesn't seem like it'd be enough time for it to properly circulate and disperse to yield a reading accurate enough to compare the next morning.

Thanks in advance!

* With the FROG Leap system, a maintenence/normal shock for our pool is 6oz of 100% cal-hypo
** A double shock is what most people without the FROG system would consider a normal shock (1oz/1k gal)

 

[JJ_Tex]

To directly answer your questions:
1. I would focus on brushing more than vacuuming
2. Use liquid chlorine as it will be incorporated faster into the pool, but for the most part most chemical additions are mixed into the pool within 30 minutes.

Now a couple of questions/key points for you:
1. How are you testing your water? Your own quality test kit is key to getting good results.
2. Can you post a full set of test results? "Perfectly balanced" doesnt tell us much and algae should not occur in perfectly balanced water.
3. Please re-read the SLAM article a few more times, especially the FC/CYA levels. Many new people have the old school thinking of a fixed FC level of 1-4 and I fear that is the case here.
4. FROG systems are not recommended here. Liquid chlorine is the recommended chlorination method or a SWCG.
5. A "maintenance shock" is not needed in properly chlorinated water, and 6oz of cal hypo isn't going to do much in your pool. By my math, that adds FC of 2.5, which is less than most pools lose in a day. A "double shock" is also a meaningless term and not going to add much chlorine to your pool.

 

[Mdragger88]

Gollie,
Re read the SLAM Process article- it says to brush & or vac daily.
You most certainly can vac that debris to filter or waste if you wish. So long as you are brushing or vacuuming daily.
Also- frog or not (we recommend not)
Slam/shock level is based on your cya period not an arbitrary number that only considers your pool’s volume.

To clarify- The slam process is also to be done with liquid chlorine not cal hypo as cal hypo adds calcium and too much calcium causes scaling.
The slam process is not a one time addition - it is maintaining slam level fc for your cya until you pass ALL 3 end of slam criteria.
This is best accomplished by testing fc & replenishing to slam level multiple times per day - every couple hours if you can swing it.
Testing at least 30 minutes after an addition is enough time for chlorine to be circulated & dispersed throughout the entire pool.
I recommend you remove the frog
It adds cya daily & metals (if you use those packs).
What are your most recent test results?
Fc
Cc
Ph
Ta
Ch
Cya

 

[Gollie]

To directly answer your questions:
1. I would focus on brushing more than vacuuming
2. Use liquid chlorine as it will be incorporated faster into the pool, but for the most part most chemical additions are mixed into the pool within 30 minutes.

Now a couple of questions/key points for you:
1. How are you testing your water? Your own quality test kit is key to getting good results.
2. Can you post a full set of test results? "Perfectly balanced" doesnt tell us much and algae should not occur in perfectly balanced water.
3. Please re-read the SLAM article a few more times, especially the FC/CYA levels. Many new people have the old school thinking of a fixed FC level of 1-4 and I fear that is the case here.
4. FROG systems are not recommended here. Liquid chlorine is the recommended chlorination method or a SWCG.
5. A "maintenance shock" is not needed in properly chlorinated water, and 6oz of cal hypo isn't going to do much in your pool. By my math, that adds FC of 2.5, which is less than most pools lose in a day. A "double shock" is also a meaningless term and not going to add much chlorine to your pool.

EDIT: FC is actually 7.5 now (3.5 was from test I did <24 hrs ago).

Thank you!!! Answers/additional info below.

When you say liquid chlorine, we're just talking about bleach, correct (unscented, NOT color-safe)? I've seen a lot of people on here say to go that route but I imagine with that option you have to add it nearly every day to maintain levels since it's not stabilized? Or add CYA as it's own thing, which I'm guessing is why people say to use the liquid chlorine since it gives the owner more control over CYA levels? All guesses though so please provide other reasoning if applicable bc it seems like a more expensive, complicated, and time consuming option and I'm totally overwhelmed with this pool as is ha.

1. Taylor K-2006; between TFP and r/pools I knew early on test strips are Crud and pool stores/people can't be trusted.
2. Last test before FC started getting rapidly used up:
*FC 1.5
*CC 0
*PH 7.6
*TA 130 (adjusted = approx 115)
*CYA 40-50 (on the high side of acceptable, but still ok)
*CH 160 (I know this is still lower than ideal min of 200, but is still above acceptable absolute min of 150; I was working on getting it above 200 when the FC began rapidly disappearing)
NOTE: with the exception of FC (which is now up to 3.5 PPM) all of the other numbers are still the same as of today. (CH might have gone up a little more but since test kit only does increments of 10 ppm for CH, I'm still getting the same reading.)
3. I have read the article about relationship between CYA/FC quite a few time this season. According to that, I would need to get FC to 16-20 ppm to reach sanitation level. My understanding is that levels that high can cause some pretty serious damage to liners, equipment, etc., not to mention making the pool unusable for potentially weeks until that level goes back down.
4. I get that. It came with the pool when we had it installed last fall. We are considering getting rid of it next season, but for now it's what I have to work with. I'd LOVE to go with an SWCG but can't bc too corrosive for AG pools.
5. With the exception of this algae incident, my pool has consistently maintained 1-3 ppm FC (and 0 CC) all season thanks to the FROG. This is the first time I've had to add chlorine via any other method since we opened the pool in May.

 

[Gollie]

Gollie,
Re read the SLAM Process article- it says to brush & or vac daily.
You most certainly can vac that debris to filter or waste if you wish. So long as you are brushing or vacuuming daily.
Also- frog or not (we recommend not)
Slam/shock level is based on your cya period not an arbitrary number that only considers your pool’s volume.
View attachment 523362
To clarify- The slam process is also to be done with liquid chlorine not cal hypo as cal hypo adds calcium and too much calcium causes scaling.
The slam process is not a one time addition - it is maintaining slam level fc for your cya until you pass ALL 3 end of slam criteria.
This is best accomplished by testing fc & replenishing to slam level multiple times per day - every couple hours if you can swing it.
Testing at least 30 minutes after an addition is enough time for chlorine to be circulated & dispersed throughout the entire pool.
I recommend you remove the frog
It adds cya daily & metals (if you use those packs).
What are your most recent test results?
Fc
Cc
Ph
Ta
Ch
Cya

EDIT: forgot to mention I'm not worried about using cal-hypo to shock bc my CH levels can/should be a bit higher anyway

Thank you! Please see my reply to JJ_Tex above. You both provided very knowledgeable, similar replies so don't want to copy/paste the same reply twice.

I'm also going to take a picture and see if I can figure out how to add that. It's really not bad, but my goal is to deal with it now before it becomes a full-bloom problem.

 

[Gollie]

I couldn't get the picture upload button to work so I had to add as an attachment; hopefully the pic is visible. The stuff at the bottom in the middle is a lot of tree debris and some algae. So, like I said, not bad (yet) but I'm not messing around when it comes to this.

 

[Brian PacNW]

3. I have read the article about relationship between CYA/FC quite a few time this season. According to that, I would need to get FC to 16-20 ppm to reach sanitation level. My understanding is that levels that high can cause some pretty serious damage to liners, equipment, etc., not to mention making the pool unusable for potentially weeks until that level goes back down.

My family has been swimming in 15-18 ppm chlorine for the better part of a week. Seemed scary at first, but anything at or below SLAM level is fine.

 

[JJ_Tex]

Thank you!!! Answers/additional info below.

When you say liquid chlorine, we're just talking about bleach, correct (unscented, NOT color-safe)? I've seen a lot of people on here say to go that route but I imagine with that option you have to add it nearly every day to maintain levels since it's not stabilized? Or add CYA as it's own thing, which I'm guessing is why people say to use the liquid chlorine since it gives the owner more control over CYA levels? All guesses though so please provide other reasoning if applicable bc it seems like a more expensive, complicated, and time consuming option and I'm totally overwhelmed with this pool as is ha.

1. Taylor K-2006; between TFP and r/pools I knew early on test strips are Crud and pool stores/people can't be trusted.
2. Last test before FC started getting rapidly used up:
*FC 1.5
*CC 0
*PH 7.6
*TA 130 (adjusted = approx 115)
*CYA 40-50 (on the high side of acceptable, but still ok)
*CH 160 (I know this is still lower than ideal min of 200, but is still above acceptable absolute min of 150; I was working on getting it above 200 when the FC began rapidly disappearing)
NOTE: with the exception of FC (which is now up to 3.5 PPM) all of the other numbers are still the same as of today. (CH might have gone up a little more but since test kit only does increments of 10 ppm for CH, I'm still getting the same reading.)
3. I have read the article about relationship between CYA/FC quite a few time this season. According to that, I would need to get FC to 16-20 ppm to reach sanitation level. My understanding is that levels that high can cause some pretty serious damage to liners, equipment, etc., not to mention making the pool unusable for potentially weeks until that level goes back down.
4. I get that. It came with the pool when we had it installed last fall. We are considering getting rid of it next season, but for now it's what I have to work with. I'd LOVE to go with an SWCG but can't bc too corrosive for AG pools.
5. With the exception of this algae incident, my pool has consistently maintained 1-3 ppm FC (and 0 CC) all season thanks to the FROG. This is the first time I've had to add chlorine via any other method since we opened the pool in May.

Thanks. Liquid chlorine can be found at pool stores, Walmart, Home Depot etc. here Walmart has the best prices.

Note the recommended level for your cya of 50 is 6-8. You are keeping your FC too low and the FROG is helping mask the problem, but that’s the problem with those mineral systems. They mask the issue until the problem becomes visible and/or cause staining on your pool surface, green hair, etc.

 

[Mdragger88]

EDIT: FC is actually 7.5 now (3.5 was from test I did <24 hrs ago).

Thank you!!! Answers/additional info below.

When you say liquid chlorine, we're just talking about bleach, correct (unscented, NOT color-safe)?

Yes- plain bleach / sodium hypochlorite (no splashless, scented, or cloromax technology/fabric conditioners) or you can just use dedicated pool liquid chlorine (in the pool section of Home Depot/lowes/ace/menards/walmart as it’s unadulterated & generally 10% sodium hypochlorite or higher so you don’t have to use as much as compared to 6%or 7% household bleach

I've seen a lot of people on here say to go that route but I imagine with that option you have to add it nearly every day to maintain levels since it's not stabilized?

The pool eats everyday (average 2-5ppm when algae free) whether you feed it or not. Tabs & the frog packs feed it slowly as they erode- maintaining a steady amount of chlorine (although usually not fast enough to keep up the pace) the stabilizer being in them is not what makes this occur it’s their physical nature. Once the stabilizer/cya is in the water it doesn’t leave (unless you replace water) so if you use liquid chlorine now with the cya being in the water the fc consumption will be the same.

Or add CYA as it's own thing, which I'm guessing is why people say to use the liquid chlorine since it gives the owner more control over CYA levels?

Yes- controlling the parameters separately is vastly easier than using a multi functional product.
Trichlor raises fc & cya & it is also acidic so then you’re dealing with ever increasing cya, the pucks or packs can’t maintain the increasing fc level necessary so you get algae/ear infections etc. + you have to deal with fluctuations in ph & ta. It creates many moving targets.

All guesses though so please provide other reasoning if applicable bc it seems like a more expensive, complicated, and time consuming option and I'm totally overwhelmed with this pool as is ha.

When you stop moving all the targets with a multi function product then you just need to focus on fc daily & managing ph if/when it rises.
The other parameters don’t fluctuate much.
When in maintenance mode (after slam) you can learn how your pool eats & feed it accordingly.
You don’t necessarily have to dose daily so long as you never allow fc to fall below minimum for your cya between doses.
The only thing cheaper than liquid chlorine is a salt water chlorine generator which carries a larger upfront expense because you’re buying 5-8 seasons worth of chlorine all at once.

1. Taylor K-2006; between TFP and r/pools I knew early on test strips are Crud and pool stores/people can't be trusted.

Smart cookie!

2. Last test before FC started getting rapidly used up:
*FC 1.5
*CC 0
*PH 7.6
*TA 130 (adjusted = approx 115)
*CYA 40-50 (on the high side of acceptable, but still ok)
*CH 160 (I know this is still lower than ideal min of 200, but is still above acceptable absolute min of 150; I was working on getting it above 200 when the FC began rapidly disappearing)

Your ch is fine- you don’t need more. You’re in the “do not add” category.
Low ch is of no concern for a vinyl lined pool unless you maybe have a heater warranty to satisfy but too high of ch is a problem with all pool surface types.

NOTE: with the exception of FC (which is now up to 3.5 PPM) all of the other numbers are still the same as of today. (CH might have gone up a little more but since test kit only does increments of 10 ppm for CH, I'm still getting the same reading.)
3. I have read the article about relationship between CYA/FC quite a few time this season. According to that, I would need to get FC to 16-20 ppm to reach sanitation level. My understanding is that levels that high can cause some pretty serious damage to liners, equipment, etc., not to mention making the pool unusable for potentially weeks until that level goes back down.

Your cya counts as 50 for chlorination purposes (always round up if between)
So Shock/Slam level is 20ppm.
It is safe for swimmers, surfaces, & equipment with fc anywhere between minimum & slam level for your cya so long as you can see the bottom of the pool for swimmer safety. You can totally use the pool.

4. I get that. It came with the pool when we had it installed last fall. We are considering getting rid of it next season, but for now it's what I have to work with. I'd LOVE to go with an SWCG but can't bc too corrosive for AG pools.

Your pool looks to be a hybrid/resin pool (resin top rails) & shouldn’t have any issues with the low levels of salt required to operate a salt water chlorine generator.
All steel walls are susceptible to corrosion from contact with water/moisture swcg or not.
All forms of manually added chlorine add salt to the water as well as acid & calcium chloride. After a few years non swcg pools can have the same salinity levels as needed to operate a swcg if they don’t exchange much water.

5. With the exception of this algae incident, my pool has consistently maintained 1-3 ppm FC (and 0 CC) all season thanks to the FROG. This is the first time I've had to add chlorine via any other method since we opened the pool in May.

1-3ppm fc is only enough with none or the very lowest levels of cya.
You have been under chlorinating / under sanitizing your pool.
Clear water doesn’t automatically = sanitary water. While the “minerals” aka metals in the frog may keep algae at bay at lower fc levels, algae though unsightly, is harmless but it serves sort of as the canary in the coal mine because if algae is proliferating so is everything else. The “minerals” kill your canary so it can’t sing.
Pathogens are invisible & person to person transmission of pathogens is a very real risk in an under sanitized body of water. My advice is to remove the packs from the frog today. Not to mention that they are one of the most expensive ways to chlorinate a pool.

I know it’s alot to take in but the synopsis is:
*Ditch the frog
*Do the SLAM Process with liquid chlorine
* Maintain adequate fc for your cya at all times therafter & no more algae troubles.

For the slam -
continue to MAINTAIN Slam level fc for your cya (20ppm) as often as possible (multiple times per day is best) until you meet ALL 3 end of slam criteria-

You are done when:
CC is 0.5 or lower;
You pass an Overnight Chlorine Loss Test
AND
The water is clear.
(Crystal Clear w/no algae dead or alive)

Do all the things
*Check & scrub every nook & cranny where algae may hide (light niches, steps(inside & out), drain covers, ladder handrails, skimmer throats/weirs, abandoned lines, autofill, overflow drains, etc.)
*If water can go there, algae can thrive there.
*Run slam level water through all water features & lines for at least a couple hours a day during the SLAM Process.
*Brush & or vac daily (this breaks up biofilms that algae uses to protect itself from chlorine)
*Backwash/clean filter when pressure rises 25%over clean pressure.

Slam on