how quickly will FC decrease after a SLAM and shouldn't you keep the CYA on lower end to not have to use as much chlorine?

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outdoorsgal

LifeTime Supporter
Jan 24, 2015
943
Phoenix, AZ
On 6-30 spotted a few "black" spots at the bottom of our salt pool. After $200 worth of chlorine and an overnight with only .5 loss of FC and I threw in another gallon after that for good measure, I thought I completed a successful SLAM on 7-5. I felt the FC levels were going down so quickly but figured my CYA was already low and FC can't maintain that high just with a salt generator so I hoped it was just going down pretty quickly to lower levels. Afterall, I knew I didn't have a lot of CYA in the pool but I always get a bit confused when I ultimately go into a pool store and they tell me I have enough, I know I have to maintain higher chlorine if CYA is higher, and this page on TFP Chlorine / CYA Chart I was within range. I realize in other places TFP says I should have between 60 and 90.

my CYA 25 (my test)/ 40 (leslie's test)

So, my FC:
7-5 24.5
7-6 14
7-7 11
7-8 7.5
7-9 10
7-10- 7
7-11-7
7-12- 4
7-13 -4
7-14- 3
7-15- 2.5
7-16- 2.5
7-17- 1.5- turned cell to 100%- oops-did I get algae here?
7-18- 3
7-20-3
7-22- 3- left on a 2.5 day trip- kept salt generator at 100% but should've added some shock/chlorine or raised CYA a long x ago-should've checked how long pool is running...? should've brushed pool better due to leaves being on bottom due to monsoon and should've been on top of my DE filter cleaning but waiting for appt next Monday for pool company to look at piston valve and break down DE filter (first time we r paying someone which also is delaying the backwash...)
seems to me this is when algae started forming again since FC got under 2?
7-25-back from trip-3pm= .5-uh oh. added 1/2 gal chlorine and 8 oz of r-0013 into the pool (yes u read right-multitasking with kids and thought it was my bottle of pool h20)
7-25 10pm= 1.5
7-26 8:15 am=1.add bag of shock.
7-26 11am fc= 4.5- spotted 3 spots of black algae at the bottom and daughter is under water brushing with a metal brush..

new bottle of r-0013 should arrive tomorrow. I have 1.5 gallons of chlorine on hand. I leave again this weekend so I'm trying to figure out when to SLAM again. I don't really want to raise CYA now if I have to SLAM cuz it'll be more chlorine but I know I need it to keep the chlorine in the pool. I've struggled with this concept since I've had the pool so if someone can explain if I should raise CYA and how much before SLAM or after and does it seem I never really got rid of the black algae before or did I get it again and when that'd be great! Also, I'm sure it was a bunch of different things that contributed but I never thought that leaves in a pool would matter THAT much, or a full DE filter. They do matter THAT much, don't they? I know I didn't mention the weather and sunny days but I think my pool was staying afloat during those days and the full DE filter/leaves in pool was what made the salt system not be able to keep up but with my levels, what do u think?

PS. the pool company that's coming out to clean DE filter and look at piston valve for backwash will want to add algaeside for algae. I've never tried it due to risks of copper staining... but somexs when I go through this I wonder if I should give it a try. Does anyone here EVER use algaeside or do I just stick to a good ol plain SLAM at all times? At less than $65 for algaeside it's tempting.

Thanks!
 
Last edited:
It's definitely helpful to do a SLAM at 30 cya versus 80 but in Phoenix, you can't realistically keep cya at 30 on a regular basis. Your SWG simply won't keep up with the daily FC loss.

The idea is to keep chlorine levels in range so you don't need to SLAM but if you do need to while your CYA is 80, it's going to take a lot more chlorine to initially get to SLAM level. Maintaining at SLAM level will also require a bit more chlorine but not a significant amount.

Regarding algaecide, it's not needed as long as you maintain proper chlorine levels. If using algaecide, you do want to ensure it's not copper based as most cheap ones are.

Complete a full SLAM, ensure you pass the criteria to end it and then increase cya to 80-90 and maintain chlorine per FC/CYA Levels
 
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outdoorsgal said:
On 6-30 spotted a few "black" spots at the bottom of our salt pool. After $200 worth of chlorine and an overnight with only .5 loss of FC and I threw in another gallon after that for good measure, I thought I completed a successful SLAM on 7-5. I felt the FC levels were going down so quickly but figured my CYA was already low and FC can't maintain that high just with a salt generator so I hoped it was just going down pretty quickly to lower levels. Afterall, I knew I didn't have a lot of CYA in the pool but I always get a bit confused when I ultimately go into a pool store and they tell me I have enough, I know I have to maintain higher chlorine if CYA is higher, and this page on TFP Chlorine / CYA Chart I was within range. I realize in other places TFP says I should have between 60 and 90.

my CYA 25 (my test)/ 40 (leslie's test)

So, my FC:
7-5 24.5
7-6 14
7-7 11
7-8 7.5
7-9 10
7-10- 7
7-11-7
7-12- 4
7-13 -4
7-14- 3
7-15- 2.5
7-16- 2.5
7-17- 1.5- turned cell to 100%- oops-did I get algae here?
7-18- 3
7-20-3
7-22- 3- left on a 2.5 day trip- kept salt generator at 100% but should've added some shock/chlorine or raised CYA a long x ago-should've checked how long pool is running...? should've brushed pool better due to leaves being on bottom due to monsoon and should've been on top of my DE filter cleaning but waiting for appt next Monday for pool company to look at piston valve and break down DE filter (first time we r paying someone which also is delaying the backwash...)
seems to me this is when algae started forming again since FC got under 2?
7-25-back from trip-3pm= .5-uh oh. added 1/2 gal chlorine and 8 oz of r-0013 into the pool (yes u read right-multitasking with kids and thought it was my bottle of pool h20)
7-25 10pm= 1.5
7-26 8:15 am=1.add bag of shock.
7-26 11am fc= 4.5- spotted 3 spots of black algae at the bottom and daughter is under water brushing with a metal brush..

new bottle of r-0013 should arrive tomorrow. I have 1.5 gallons of chlorine on hand. I leave again this weekend so I'm trying to figure out when to SLAM again. I don't really want to raise CYA now if I have to SLAM cuz it'll be more chlorine but I know I need it to keep the chlorine in the pool. I've struggled with this concept since I've had the pool so if someone can explain if I should raise CYA and how much before SLAM or after and does it seem I never really got rid of the black algae before or did I get it again and when that'd be great! Also, I'm sure it was a bunch of different things that contributed but I never thought that leaves in a pool would matter THAT much, or a full DE filter. They do matter THAT much, don't they? I know I didn't mention the weather and sunny days but I think my pool was staying afloat during those days and the full DE filter/leaves in pool was what made the salt system not be able to keep up but with my levels, what do u think?

PS. the pool company that's coming out to clean DE filter and look at piston valve for backwash will want to add algaeside for algae. I've never tried it due to risks of copper staining... but somexs when I go through this I wonder if I should give it a try. Does anyone here EVER use algaeside or do I just stick to a good ol plain SLAM at all times? At less than $65 for algaeside it's tempting.

Thanks!
Click to expand...
If you’re still using the UV, that will degrade chlorine a little bit and I’d expect it to not be needed in AZ especially if your pool is already getting lots of sun.

Your signature says you had a T15 cell and not you have a 40K cell with same controller? Have you verified what the new cell is actually producing with a overnight chlorine gain test?
 
Sunnydaze,, thx. the chart you sent me said anything 70 and above or 20 and below is out of range. This link SLAM - Shock Level and Maintain says SLAMing is best with CYA around 30 or 40, impractical around 80 and empty water at 90. This link, though ABC's of Pool Water Chemistry, says SWG 60-90. U r also in AZ, so my guess is you keep yours at 80-90? That's a huge jump for me but I also go through this every year so I've gotta learn somex. If I'm correct, what u and TFP are saying is don't increase my CYA yet until after the SLAM and then 80-90. TFP's 60- 80 won't cut it? I'll try for 80.
 
Bperry, brand new salt cell (March). I'll say I wasn't doing the greatest of testing at the time until first algae outbreak that I mentioned. Salt cell was on 30. We had a generic jacuzzi brand salt cell for a while and a panel that had burnt out. worst idea to get a cheap jacuzzi salt cell-It would've cost less $ to get the hayward in the end, with the problems we had with it. We also have a brand new panel (March). I have not verified what the cell is producing with an overnight test. u mean when the pool doesn't have algae, correct? If u mean now that I have algae, it lost .5 from 10pm to 8:15 am, which sun was up, but was cloudy. I didn't pay attention if direct light was on the pool since I wasn't being very serious about an overnight test. I was just getting an idea.

I never thought of unplugging the UV. If it will help make a dent in killing algae I'll leave it plugged in. I get what u r saying about eating up chlorine. great point. I regret getting the UV but I have it, so yes, I still use it after the $$$ "investment." :(

I'm not quite sure what u mean about the cell and controller but I need to upgrade my signature. I have a hayward turbocell tcell940 extended life cell 4 yr warranty for up to 40k gallons. I have a hayward panel and a puck.
thx!
 
outdoorsgal said:
Sunnydaze,, thx. the chart you sent me said anything 70 and above or 20 and below is out of range. This link SLAM - Shock Level and Maintain says SLAMing is best with CYA around 30 or 40, impractical around 80 and empty water at 90. This link, though ABC's of Pool Water Chemistry, says SWG 60-90. U r also in AZ, so my guess is you keep yours at 80-90? That's a huge jump for me but I also go through this every year so I've gotta learn somex. If I'm correct, what u and TFP are saying is don't increase my CYA yet until after the SLAM and then 80-90. TFP's 60- 80 won't cut it? I'll try for 80.
Click to expand...

Salt water pools do well with higher cya levels. I don't have a salt pool and I keep cya at 60. Being in AZ, you'll see less chlorine loss on the high end of the recommended levels. But you're correct, don't increase cya until after the SLAM is complete.
 
Kim

Nice to see you back this year.

Post a full set of current test results from your TF100 or K2006C testkit ksorry, can't remember which you have). Also post your salt number from a test kit, jot the SWG controller.

How old are your test kit reagents?

I see you are sharing your PoolMath logs, but no current entries in 3 years. Either post results in PoolMath or post them here as follows....

FC
CC
pH
TA
CH
CYA
Salt
Water temperature

As has been mentioned, with a working SWG, you should have a CYA of 70.

Oh, one more thing - stay out of the pool store. They are only adding confusion and looking to take your money.
 
outdoorsgal said:
Bperry, brand new salt cell (March). I'll say I wasn't doing the greatest of testing at the time until first algae outbreak that I mentioned. Salt cell was on 30. We had a generic jacuzzi brand salt cell for a while and a panel that had burnt out. worst idea to get a cheap jacuzzi salt cell-It would've cost less $ to get the hayward in the end, with the problems we had with it. We also have a brand new panel (March). I have not verified what the cell is producing with an overnight test. u mean when the pool doesn't have algae, correct? If u mean now that I have algae, it lost .5 from 10pm to 8:15 am, which sun was up, but was cloudy. I didn't pay attention if direct light was on the pool since I wasn't being very serious about an overnight test. I was just getting an idea.

I never thought of unplugging the UV. If it will help make a dent in killing algae I'll leave it plugged in. I get what u r saying about eating up chlorine. great point. I regret getting the UV but I have it, so yes, I still use it after the $$$ "investment." :(

I'm not quite sure what u mean about the cell and controller but I need to upgrade my signature. I have a hayward turbocell tcell940 extended life cell 4 yr warranty for up to 40k gallons. I have a hayward panel and a puck.
thx!
Click to expand...
I’d the water has algae or is cloudy now, then it doesn’t have enough chlorine in it. So your stuck with the SLAM process now.

There’s no need for algaecide, chlorine will do the job. Letting it get so low is why you have the algae so make sure not to get it so low again when it’s fixed.

When that’s done and you have a concern that the SWCG is working or not, you can run your SWCG overnight, all night at 100% to see how much chlorine it generates when the sun isn’t shining to make sure it’s doing what it’s supposed to.
 

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proavia said:
Kim

Nice to see you back this year.

Post a full set of current test results from your TF100 or K2006C testkit ksorry, can't remember which you have). Also post your salt number from a test kit, jot the SWG controller.

How old are your test kit reagents?

I see you are sharing your PoolMath logs, but no current entries in 3 years. Either post results in PoolMath or post them here as follows....

FC
CC
pH
TA
CH
CYA
Salt
Water temperature

As has been mentioned, with a working SWG, you should have a CYA of 70.

Oh, one more thing - stay out of the pool store. They are only adding confusion and looking to take your money.
Click to expand...
Hi Gene, I'm surprised u have the patience to reply to me after all of these years. :) I didn't know I was sharing my poolmath. I use the old one. I can't remember what it was about the new one but I didn't like it. I think it was that you had to check TA everyx or more things than I want to. It's likely there's a way around that and I didn't do it right.

My r-0013 arrived today after my mistake of dumping it in the water. My r-0870/1 r a couple mths old. The rest is from last year, I believe. This x I made note to get it in March for the sale for next year, though.

Here's the latest since last x I shared in this post:

superchlorinator on
FC:
7-26:
8:18am 1. put 1/2 gallon chlorine
11 am 4.5
3pm 1
6:20pm put 1.5 gall chlorine
midnight 6.5/7

7-27:
8:05am 6.5/7
12:35 pm 5
2:55p 4.5
NO CHLORINE ADDED TODAY. SUPER CHLORINATOR KEEPING UP, although says "no flow" and "chlorinator off" even though says "superchlorinator on."

full measure at 2:55:
FC= 4.5
CC= 0
pH= 7.5
TA= 130 (disappointing as I've been adding acid to get it to 7.2 every other day or so for the past mth of so)
CH=560
CYA=50 checked it twice. I had added stabilizer after last x it turned green. I forgot to mention that. Since pool store said wait a week to retest I then blew it off as I felt too cocky testing water daily
Salt=4600 was when it settled into red brick but the first glimpses of salmon red was 3200. Last time I checked and the last repair guy, it was on the high range, closer to the 3200 #. repair guy said he felt comfortable warranteeing the cell cuz he said it'd be within range in a couple of backwashes.
Water temperature 89 cell temp/91 water temp

I know, uk've told lme to stay out of pool store before. I was going to have pool supply store tear down my DE filter and look at my piston valve since we already changed O rings and hubby hasn't had x to clean DE filter. We've done much better paying the last company to warranty and replace our mother board and our salt cell after so much time, headache, and money of cell and board not creating chlorine, getting it welded, still didn't work, sending it to OK, breaking an important part off of a new board (if u haven't noticed by now we try but rn't that handy many xs). Neighbor recommended this place and over the phone she mentioned algaeside and they'd treat the pool. I cancelled the appt as I didn't trust or like what I heard. I have wondered about algaesides, though, since she said $65 at most to kill the algae with algaeside. I spent $200 on chlorine and shock last x. I bought another $100 at HD today for this time around. We'll see if it's enough.

I'm prob going to start the SLAM Friday. I usually start right away but don't like swimming in high levels of FC and I figure I may learn something watching my SWG hold it's own right now. Interesting. I just hope I'm not making the algae "immune" to this level of chlorine. I don't think it works that way. I hope I'm slowly killing it and preventing more by keeping #s in fair range. I'm glad I caught it early. I can tell by the color of the h20 each time, though. Each x I say it's' the last. I'm getting better but not good enough. I told my 14 yo he gets $1 each x he checks the FC and ph so he's been checking. I watched to make mostly sure cuz he tries to get away without perfection and u sort of need that when measuring chemicals.

Not sure what u mean about jot the SWG controller. My panel, cell, and puck r up to date in my signature.

thx!
 
outdoorsgal said:
Salt=4600 was when it settled into red brick but the first glimpses of salmon red was 3200.
Click to expand...
The instructions should be clear that you stop adding drops when the color permanently switches from yellow/white to some kind of brick/salmon/red/pink/etc. don’t keep adding drops after that. Your salt is 3200ppm.
 
outdoorsgal said:
Hi Gene, I'm surprised u have the patience to reply to me after all of these years. :)
Click to expand...
Ha - I decided to check my patience threshold again. :ROFLMAO: :ROFLMAO: :ROFLMAO: :ROFLMAO: :ROFLMAO:

Algaecide might help prevent algae. Eradicating it, not so much. But you already knew that.

Please, please, please - don't use shorthand in your posts. It makes them very difficult to read thru.

Leave the CYA where is is for now. You can raise it after the SLAM Process is completed.

Don't forget to shut off your SWG during the SLAM Process. You need to learn the process better without using the SWG as a crutch. Be sure to follow the SLAM Process to the letter - NO SHORTCUTS.

When posting current results, post as follows and put the results directly after the letters for the result...

FC
CC
pH
TA
CH
CYA
Salt
Water temp

Again, follow the SLAM Process instructions.
With CYA of 50, SLAM Process is 20 for FC.
It is completed safe to swim when FC is minimum and SLAM level FC according to the FC/CYA Levels and you can see the bottom of the pool at all water depths.
 
outdoorsgal said:
interesting. so is this showing it's best to be between 70 and 90 for a SLAM with SWG?
Click to expand...

No, the chart shown by Sunnydaze is for normal SWG operation. There are three buttons in the screenshot, the one in green (SWG) being the active one that the table refers to.

SLAM levels are identical for liquid chlorine and SWG (during a SLAM, you'd turn off the SWG anyway and use liquid chlorine).

That's how the SLAM chart looks like:

Screenshot_20220728-203024-766.png


In normal operation, higher CYA results in less daily chlorine loss due to UV even though the required FC level is higher. Once you reached that higher FC level, you have to add less chlorine per day to maintain that higher FC level compared to maintaining the lower chlorine level that would be required at lower CYA.

Therefore, higher CYA is always more economical in normal operation mode, theoretically also for liquid chlorine pools, not just for SWG-pools.

The downside of high CYA is that, should you ever have to SLAM, you need much higher SLAM-FC levels, no matter whether it's a liquid chlorine or a SWG pool.

With a well dialled in SWG, it's very unlikely that you ever have to SLAM the pool, due to the regular and reliable chlorination, and it's worth taking the benefits of higher CYA during normal operation - the SWG can be run on a lower percentage which will extend its lifetime.

With a liquid chlorine pool it is more likely to miss a chlorine addition sooner or later, letting FC slip below min, and ending up having to SLAM. Since a SLAM is very difficult with CYA 80, TFP doesn't recommend those higher CYA levels for liquid chlorine pools.
 

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Bperry said:
The instructions should be clear that you stop adding drops when the color permanently switches from yellow/white to some kind of brick/salmon/red/pink/etc. don’t keep adding drops after that. Your salt is 3200ppm.
Click to expand...
it didn't permanently switch from yellow/white which his why I was worried about the higher number. it turned for a sec, but for the whole liquid to turn an obvious different color it was 4600. After 4600 I don't think the color would go any darker, though and I've had it tested by guy who installed the new panel and salt cell, so I feel ok about the lower number, but I don't feel confident about my testing as far as salt, since it just turns for 1/2 a second
 
mgtfp said:
With a liquid chlorine pool it is more likely to miss a chlorine addition sooner or later, letting FC slip below min, and ending up having to SLAM. Since a SLAM is very difficult with CYA 80, TFP doesn't recommend those higher CYA levels for liquid chlorine pools
Click to expand...
I was curious about why SWG is recommended to have higher CYA. That explains that, which makes me feel even worse about having to SLAM twice in a month with SWG! I was trying to save on my salt cell. oh well. thx
 
Proavia, thx for all the good info! I'm on it!

Now, back to the intent of my post, in my original post/FC#s, can anyone let me know where they think I got algae? As far as I followed the SLAM process to the T last time and passed an OCLT. With that, could it be I didn't get rid of the algae completely or r we thinking it reoccured when it dropped between the ideal amount, either when I went out of town or anywhere after 7-14? I think I had it in my head where it says if your fc goes to zero SLAM - Shock Level and Maintain u need to SLAM. Really, I probably need to focus on CYA/chlorine chart where it says "if your FC goes to less than the minimum amount I'm in danger of/probably have algae. Is that correct and did my FC seem to drop at a normal speed after I was done SLAMming? (It dropped 10 FCs the first day).

thx!
 
Think of the minimum FC for a given CYA as falling off a cliff. Nothing most of us would choose to do. If you fall, chances are algae and another SLAM.
Maintain FC at or slightly above target range and NEVER, EVER let it go below minimum.

Given our super hot and mostly dry summers, evaporation and FC usage is great. Sometimes we use more FC in a day than other days (lots of swimmers, debris, etc.)
If you find your FC is getting close to minimum for your CYA, you need to dose to a higher FC daily so you don't go below minimum of the heavy swim days.

While not exactly taught or listed in the FC/CYA Levels - I tend to ALWAYS run with FC a little hot. While the SWG may get used up a little faster, I don't really have to worry about my FC dropping below minimum.
My CYA is 70 - minimum FC is 3 - Target is 5
What I shoot for - minimum FC 3 - Target 8-10 (this target is from the non-SWG part of the chart)
Having this larger buffer provides me with piece of mind and if I get busy and forget to test, I'm still good.
Remember, it is safe to swim with FC anywhere between minimum and SLAM level... For CYA 70 and a SWG pool, that is FC 3 to FC 28.
Of course, I also need to be able to see the entire bottom of my pool from the shallow end to the deep end.

As I recall, you have always been a bit apprehensive of "higher" FC levels. And that apprehension is still continuing to get you in trouble.
It's time to go all in and swim in the TFP Pool-Aid. Follow the sage advice provided to you for all these years over 7 years now. It will make your busy life a lot simpler.
 
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^^^ this

You'll get the hang of it. Once your SWG is dialled in following this philosophy, SLAMs should just be a story to tell the grandkids.

Pay particular attention at the beginning of each season when days are still getting longer. That's when the SWG needs cranking up. And backwards again at the end of the season, but then the only risk is to overshoot which is not really critical - remember: you can safely swim up to SLAM-FC.
 
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outdoorsgal said:
it didn't permanently switch from yellow/white which his why I was worried about the higher number. it turned for a sec, but for the whole liquid to turn an obvious different color it was 4600. After 4600 I don't think the color would go any darker, though and I've had it tested by guy who installed the new panel and salt cell, so I feel ok about the lower number, but I don't feel confident about my testing as far as salt, since it just turns for 1/2 a second
Click to expand...
are you using a speedstir? It’s always been pretty instantaneous for me. It’ll start to turn red but as it swirls it’ll turn back to the original color. Then on the next drop, bam! it switches to red. There should be no ambiguity on when that happens. Unless you’ve accidentally filled the tube to 25ml instead of 10ml? That gets a lot of people cause the instructions kinda fool you.
 

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