Second Visible Algae Event in 3 months

RexO

Well-known member
May 24, 2020
52
Melbourne, FL
Hi All,

My question up front: Why am I getting algae while following the TFP method?
I noticed my 2nd visible algae event in just 3 months after returning from a week long trip away from home.
A week ago, in anticipation of the week long trip; I left the pool at these levels:
FC: 8 (boosted it above target to stay safe) Left the SWCG to produce 3 FC per day (8 hours/75%) which was holding steady FC before I left.
CYA:70
PH: 7.5
TA: 70
Calcium:375
Salt: 3600
On day 5, I asked my neighbor to add 8 ounces of Acid. Based on history, I know the PH would be creeping up towards, 8.0 but wanted to treated lightly since he was not testing.
Upon returning, just before sunset, I noticed what looked to be light algae in some areas. I tested with these results:
FC:5.5
CYA:70
PH: 7.8
TA: 70
Calcium:375
Salt:3600
Because of the lighting, I was not positive of the presence of algae, but decided to conduct an OCLT. In the morning before sunrise the FC was 3.5. After sunrise, I confirm the presence of algae as it appeared light green and I could brush it off the surface. I started a SLAM this morning.

So, my question again:
Why am I getting algae? I have been using the TFP method, especially in regards to the FC/CYA ratio.

I appreciate any guidance.

Rex
 

Mdragger88

Bronze Supporter
Jun 1, 2018
2,739
Hernando, Ms
Pool Size
26000
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Vinyl
Chlorine
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Intex Krystal Clear
It may be possible that during your time away at some point the fc level dropped below min but your swg then produced enough to come back up by the time u tested. How do u run it? X % all the time or on then off for so many hrs?
It’s also possible that your most recent slam didn’t eradicate it all (ended too soon). Oversized swgs are nice but sometimes they can mask a problem if you don’t notice the chlorine demand happening because they make plenty of chlorine when they are on. When u get done with this slam you may want to be sure to test at various times of the day to see if there are dips depending on your run time settings.
 

CrystalRiver

Well-known member
Jun 19, 2020
648
Massachusetts
What time of day does your SWG run? It's possible your FC was dropping down to 3ish, then SWG adds 3, you test and it says 5.5 and wonder why you have a problem. The problem was all those hours at 3.

The charts are a guide. If *your* pool needs to target a higher level, then target a higher level. My target and minimum numbers are the same as yours. I test at the lowest FC point of the day, and I never want to see a reading below 5. That bit between 3 (chart minimum) and 5 (my minimum) is a buffer to protect against bacteria and viruses in case my FC slips below 5, but it's not something I use on a regular basis.
 
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RexO

Well-known member
May 24, 2020
52
Melbourne, FL
What time of day does your SWG run? It's possible your FC was dropping down to 3ish, then SWG adds 3, you test and it says 5.5 and wonder why you have a problem. The problem was all those hours at 3.

The charts are a guide. If *your* pool needs to target a higher level, then target a higher level. My target and minimum numbers are the same as yours. I test at the lowest FC point of the day, and I never want to see a reading below 5. That bit between 3 (chart minimum) and 5 (my minimum) is a buffer to protect against bacteria and viruses in case my FC slips below 5, but it's not something I use on a regular basis.
Hi, thanks for the reply. Since the previous SLAM, I have been using 5 as an absolute min for FC. I was holding 6-7 for several weeks and targeted 8 for the week I was away. When I say 6-7 ppm, that is what I see in the morning before the SWCG comes on at 9 AM. I have been running the SWCG from 9 AM to 5 PM....Melbourne, FL. So, I figured it is not going below 6-7 during the day while chlorine is being made. The pool water temp has been from 78 - 85 before I left. The week I was gone, there was no testing, so I cannot realty say what was going on except that it tested a 5.5 at about 8 PM and then 3.5 the following morning. My neighbors where using the pool while I was gone, 2 adults, two children. But that is normal usage. I believe the week I was gone the temperatures did increase. The pool was 87 deg at PM, that was as warm as I have seen it this year. So that must have increased the chlorine demand greater than the 3 ppm I was adding daily. It just seems weird that the pool would test at 5.5 at 8 PM and have visible algae. I suspect the algae was just becoming visible on the last day as the chlorine demand was going up.
 

RexO

Well-known member
May 24, 2020
52
Melbourne, FL
It may be possible that during your time away at some point the fc level dropped below min but your swg then produced enough to come back up by the time u tested. How do u run it? X % all the time or on then off for so many hrs?
It’s also possible that your most recent slam didn’t eradicate it all (ended too soon). Oversized swgs are nice but sometimes they can mask a problem if you don’t notice the chlorine demand happening because they make plenty of chlorine when they are on. When u get done with this slam you may want to be sure to test at various times of the day to see if there are dips depending on your run time settings.
I am running the SWCG 75% from 9-5. Was holding good when I left for a week. But, the water temps increased over the week, so that must have increased demand about the 3 ppm I was adding daily with the SWCG. I just thought starting a 8 PPM would give me cushion to stay at 5 or above for the week.
 

Oly

Gold Supporter
Jun 28, 2017
2,282
Fresno, CA
Pool Size
27000
Adjust your VS pump to run more than 8 hours a day during peak demand. Schedule it to start before the sun is up and into the evening. Adjust the % to match your daily FC loss and test FC at night or early in the am. Keep your FC a bit higher for safety.
 
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Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
10,371
NY
Hey Rex !!!

I’ll toss my vote in for 24/7 run time. Sure 8 hours works, But it’s a mini rollercoaster with no promises. If an event happens be it weather or swimmers while the unit is off, you can easily lose your safety net. If it’s fully topped off at all times, you’ll only dip back into acceptable range.
 
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Orion7319

Well-known member
Jul 1, 2020
546
Rock Hill, South Carolina
Pool Size
19775
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
I am running my pool exactly like you are and am experiencing similar results. Last night I found a wee bit of algae hiding in some silicone around my pool stairs gasket. Like you, I run my salt cell from 9:00-5:00pm and I never see the FC levels drop below 5. My CYA is currently at 60, so I am confused why as to why I am seeing any algae at all in the pool. Based on the suggestions above it might be better to run the salt cell longer at a lower percentage then 9:00am to 5:00PM. I am going to try to lower my percentage (by whatever pool math tells me) and increase my run time from just before dawn and just after dusk. Or is it just better to run the salt cell for 24 hours straight and calculate the percentage you need over the 24 hour time span (which doesn’t seem very intuitive to me)
 
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Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
10,371
NY
Or is it just better to run the salt cell for 24 hours straight and calculate the percentage you need over the 24 hour time span (which doesn’t seem very intuitive to me)
It’s all the same if the math jibes. 12 hours at 100% or 24 hours at 50%. Or any kind of equivalent math. you will have the same runtime hours on the SWG and lose said hours off the lifespan of the unit either way.

Your pump will cost more in electric with the extra runtime but it’s about $20 a month total for most folks with a VS. would you even realize the bill was $10 higher ? I wouldn’t. :)

But. You’ll be forever topped off instead of fluctuating day/night. Even if it’s literally just a couple PPM, it’s a fluctuation and things can happen when you aren’t producing. Like losing FC overnight after a family evening swim. That could put you into the minimum range and by the time you check in the morning you have gained a little and it looks like everything was ok in the meantime.

Added skimming/filtering is a HUGE free bonus. If some leaves blow in at 3AM, they’ll float over to the skimmer instead of getting waterlogged and sink to the bottom before the pump turns back on.
 
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Orion7319

Well-known member
Jul 1, 2020
546
Rock Hill, South Carolina
Pool Size
19775
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
It’s all the same if the math jibes. 12 hours at 100% or 24 hours at 50%. Or any kind of equivalent math. you will have the same runtime hours on the SWG and lose said hours off the lifespan of the unit either way.

Your pump will cost more in electric with the extra runtime but it’s about $20 a month total for most folks with a VS. would you even realize the bill was $10 higher ? I wouldn’t. :)

But. You’ll be forever topped off instead of fluctuating day/night. Even if it’s literally just a couple PPM, it’s a fluctuation and things can happen when you aren’t producing. Like losing FC overnight after a family evening swim. That could put you into the minimum range and by the time you check in the morning you have gained a little and it looks like everything was ok in the meantime.

Added skimming/filtering is a HUGE free bonus. If some leaves blow in at 3AM, they’ll float over to the skimmer instead of getting waterlogged and sink to the bottom before the pump turns back on.
That makes sense. I was under the impression that as long as your making chlorine during the day you don’t need to make it at night because it’s not being burned off by the sun. I suppose the flaw in that logic is that algae can gain a foot hold at night if the chlorine drops a bit? Or does it have something to do with the super- chlorinated area at the salt cell itself which is why you run the CYA higher? Either way, I am already running my pump 24/7/365. I am probably going to have to set the speed a bit higher at night, but if it works a lot better and if it keeps the algae at bay then it’s well worth 50 or 100 extra watts or so…

Edit:
Just to be clear, currently I am running my salt cell at 34% at 8 hours to generate 1ppm of chlorine. If I run my cell at 11% for 24 hours I am generating 1ppm of chlorine. If you break that down to figure out how much chlorine your generating per hour, then running for 8 hours is 0.125ppm added per hour. If you run it 24 hours that’s around 0.042ppm added per hour. You don’t have to factor in daylight hours at all? Wouldn’t you be loosing more then you produce during daylight hours, or would we be producing a surplus at night that nullifies that? At any rate I’m going to just try running mine at 11% 24 hours a day for the next week and see what my levels do.
 
Last edited:

Bperry

Gold Supporter
Aug 20, 2020
782
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
Hi All,

My question up front: Why am I getting algae while following the TFP method?
I noticed my 2nd visible algae event in just 3 months after returning from a week long trip away from home.
A week ago, in anticipation of the week long trip; I left the pool at these levels:
FC: 8 (boosted it above target to stay safe) Left the SWCG to produce 3 FC per day (8 hours/75%) which was holding steady FC before I left.
CYA:70
PH: 7.5
TA: 70
Calcium:375
Salt: 3600
On day 5, I asked my neighbor to add 8 ounces of Acid. Based on history, I know the PH would be creeping up towards, 8.0 but wanted to treated lightly since he was not testing.
Upon returning, just before sunset, I noticed what looked to be light algae in some areas. I tested with these results:
FC:5.5
CYA:70
PH: 7.8
TA: 70
Calcium:375
Salt:3600
Because of the lighting, I was not positive of the presence of algae, but decided to conduct an OCLT. In the morning before sunrise the FC was 3.5. After sunrise, I confirm the presence of algae as it appeared light green and I could brush it off the surface. I started a SLAM this morning.

So, my question again:
Why am I getting algae? I have been using the TFP method, especially in regards to the FC/CYA ratio.

I appreciate any guidance.

Rex
If you lost that much FC overnight and can see algae, then that’s an obvious sign that the chlorine is lost fighting the algae. If swimmers were in the pool while you were gone, that might have eaten up some extra as well.
 

Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
10,371
NY
I suppose the flaw in that logic is that algae can gain a foot hold at night if the chlorine drops a bit?
Exactly. It’s what happens while you aren’t producing. Like an overnight storm, or the FC doing it’s thing after a party.

When you manually dose you are spiking it high and it has plenty of leeway time as it drifts down, but you still run risks if it drifts down too far before the next dose.
Or does it have something to do with the super- chlorinated area at the salt cell itself which is why you run the CYA higher
This is confusing and not as cut/dry as the rest of the TFP regimen. It’s an older way of thinking that will probably be written out of Pool School in the future IMHO.

CYA is recommended higher for the SWG to better protect that little bit that it’s constantly producing. With liquid you get a big spike that can handle a 1 FC drop here and there. With the SWG it’s easy to lose that .25 FC per hour (or whatever) to the sun and not have enough residuals for sanitizing.
Either way, I am already running my pump 24/7/365
Then you have every reason to lower the SWG runtime and let it go 24/7 with the pump. It will maintain a constantly topped off FC at your target. (Preferably the high side of in range or slightly above). Then anything can happen be it weather or a party and you always have a full safety net. If you come down 2FC due to an event, you are in range.
 
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Orion7319

Well-known member
Jul 1, 2020
546
Rock Hill, South Carolina
Pool Size
19775
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
CYA is recommended higher for the SWG to better protect that little bit that it’s constantly producing. With liquid you get a big spike that can handle a 1 FC drop here and there. With the SWG it’s easy to lose that .25 FC per hour (or whatever) to the sun and not have enough residuals for sanitizing.
That is the best, least head scratching explanation I have heard yet as to why you run a higher CYA with a salt cell! Thank you so much for that! I could not for the life of me wrap my head around this whole “you need more CYA because of the super-chlorinated area in your pipes” thing…. That makes PERFECT sense!!!!!!!! The headache that I have been giving myself when trying to contemplate why you run a higher CYA for a salt pool just went away! Lol! I’ve been running mine at 60 so when I do switch it over to run 24/7 I should certainly bump it up to 70 then… or just increase the percentage a bit over 11 until I do… at any rate thanks! You made it all make sense to me! Awesome!
 
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Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
22,612
Bedford, TX
Rex,

The FC/CYA chart levels "assume" that you do not have algae.. The normal levels are designed to keep you from getting algae, but they certainly won't kill it.

In most cases where people get repeated algae outbreaks, it is because they never killed all the algae when doing their initial SLAM.

If you have visible algae, you need to SLAM.. I suggest that you follow the SLAM process to the letter.. and if me, I'd SLAM at the next higher CYA level and for an additional 24 hours when you think you are done.

Thanks,

Jim R.
 

RexO

Well-known member
May 24, 2020
52
Melbourne, FL
Thanks for all the input. I will increase my run time and total chlorine output too as the heat is starting to ramp up. I thought I had it dialed in pretty well to avoid any problems while I was gone. Next time I am gone for a week, I think I will add some extra liquid chlorine (a notch below SLAM levels) while keeping the SWCG producing. Thinking that would still be safe for swimmers, but would give me extra protection while I am gone since the higher than normal FC levels will slowly go down over a few days.
 

Orion7319

Well-known member
Jul 1, 2020
546
Rock Hill, South Carolina
Pool Size
19775
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
So I set the salt cell to run for 24 hours yesterday evening to produce 1ppm over that timespan. Previously running the cell for 8 hours a day, setting it to produce 1ppm, I was maintaining at 5ppm. I was kind of expecting a bit of a loss after doing so and I was correct. My FC levels this evening came in at 4.5ppm. I know it’s not that critical to hit an exact number, but that is what I am trying to do, just to gain a better understanding of how this all behaves under different circumstances. This evening, I set the salt cell to generate 1.50ppm, with the goal of simply maintaining 4.5ppm over the course of 24 hours. My CYA is currently 60. Am I correct to assume that this setting will maintain that level, or will an increase of CYA to 70 be necessary to active that? The weather conditions over the last several days have been relatively consistent.
 

Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
10,371
NY
It’s plenty warm in SC by now and 70 CYA will probably do the trick. If not it’s a dance for your specific pool with adjusting the SWG % a few times over the season. Even with the 70 you’ll have to bump the runtime at some point. I’d get 4-6 weeks after each adjustment, 3 times up and 2 down.
 
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Orion7319

Well-known member
Jul 1, 2020
546
Rock Hill, South Carolina
Pool Size
19775
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
It’s plenty warm in SC by now and 70 CYA will probably do the trick. If not it’s a dance for your specific pool with adjusting the SWG % a few times over the season. Even with the 70 you’ll have to bump the runtime at some point. I’d get 4-6 weeks after each adjustment, 3 times up and 2 down.
It’s in the 90s now, but expecting cooler weather (80’s) over the weekend. My water temps just hit 80 this week and I went in the pool for the first time this week. It’s kinda weird running it around 11% and 17%. Used to cranking it up much higher. I’ll raise the CYA gradually starting this weekend though next week to creep up to 70. I don’t anticipate it getting much hotter then it currently is this summer, but it wouldn’t surprise me if this is a hot one.
 
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