Just started tfp method - pool still turning green, losing fc

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AvM

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Oct 11, 2018
9
BOCA RATON, FL
I started the tfp method last week - first draining the pool halfway which lowered the cya to 40/50, then raised to chock level - only one or two times, and the overnight test showed no lost fc. Since then, I've been raising the fc to 7 at night and by the next evening it's down to 3/3.5 and the pool starting to look green. Yesterday I tried raising it higher (9 or 10 - didn't test after to check) and the next day looking green with fc at 6.5.

My latest numbers:
fc - 6.5
cc- .5
ta - 100
cya - 40/50 (showed 50 or a bit less today - but tested while cloudy - no sun, and a few days ago I thought it was 35/40)
ch - 225

Any ideas? The algae is generally starts at the deepest end of the pool (at the opposite corner that I usually poor the chlorine) and is soon noticeable on the steps and walls.
 
AvM said:
I started the tfp method last week - first draining the pool halfway which lowered the cya to 40/50, then raised to chock level - only one or two times, and the overnight test showed no lost fc. Since then, I've been raising the fc to 7 at night and by the next evening it's down to 3/3.5 and the pool starting to look green. Yesterday I tried raising it higher (9 or 10 - didn't test after to check) and the next day looking green with fc at 6.5.

My latest numbers:
fc - 6.5
cc- .5
ta - 100
cya - 40/50 (showed 50 or a bit less today - but tested while cloudy - no sun, and a few days ago I thought it was 35/40)
ch - 225

Any ideas? The algae is generally starts at the deepest end of the pool (at the opposite corner that I usually poor the chlorine) and is soon noticeable on the steps and walls.
Click to expand...

Your pool is turning green because you are letting your FC drop too low. With a CYA of 50ppm, your FC should never go below 4ppm.

Pool School - Chlorine / CYA Chart
 
Does it make sense that I'm losing 3 or 4ppm a day just from sunlight? If yes, do I have raise it to 8 or 9 each day to make sure it doesn't go too low?
Also, do I need to SLAM again now that there's algae in the pool or would maintaining regular levels be enough to kill it?
 
As long as you have algae, you need to SLAM Process . Then once the SLAM is over your maintaining the pool based on the [FC/CYA][/FC/CYA] guide will help you prevent any future algae joining the party.

Make sure you maintain the SLAM as often through out the day as possible to eradicate the algae as fast as possible. Dosing once or twice a day is simply not enough to kill algae faster than it reproduces. You may main a few spores but the hearty spores will just keep on reproducing.

Maddie :flower:
 
Clean your filter too. See where the pressure is when it starts back up and clean again when it's 20-25% over that number.
Lots to do but it will pay off if you follow the procedure. Ask questions and post your test results to help us guide you.
 
Thanks!
Some more questions:
1) I accidentally raised the fc much higher (32 instead of 20 - I counted my 2.5 gal can as 1 gal) - do I do anything different or just wait till it goes below shock level to add more chlorine?
2) I cleaned the filter last week - If there's some new algae there (the pressure hasn't gone up yet) can that reinfect the pool?
3) Is the oclt performed with fc at shock level?
 

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You're getting excellent advice for the SLAM process. Be sure to check for and clean out any out-of-the-way places algae might be hiding, and reinfecting your pool (behind a light, in the skimmer, steps, ladders, wherever).

Once you rid the pool of algae, and return it to normal levels, remember, the recommend levels for CYA and FC are guidelines, not hard and fast rules that work in every pool. If your pool is prone to algae, then you might need to increase your FC level a point or two. And instead of relying on the minimum FC level, ignore that, and use the low end of the target range as your minimum. That'll give you a bit of a buffer that will keep you well away from "the danger zone."

Based on a CYA of 50, your minimum would be 4 and your target range is 6-8. So instead of letting your FC drop to 4 or 5 each day, do what you have to do to never let it go below 6. And if you're still getting algae, and you're sure you've completed a SLAM correctly, then up your numbers a notch. Never let it go below 7, etc.

Listen to TFP, but listen to your pool, too, it'll tell you what it needs...

All that said, you seem to be a prime candidate for a salt water chlorine generator. It'll maintain a constant level of FC, throughout the day, and once setup correctly, it'll virtually never let your FC fall too low. Plus they are crazy convenient!
 
Oh, and there's another possibility for your reoccurring algae. If you don't have your pool's water volume number correct, you might only think you're dosing enough chlorine. After your SLAM is complete and things settle down, and you're sure your pool is free of organic material, try this, after the sun goes down. Test your FC, then use Pool Math to determine the dose of chlorine to restore your FC level. Add that dose to the pool and circulate the water well for 30-60 minutes. Test the FC again, as soon as you think it's mixed in well. If you get the expected result, then your water volume number is OK. If you consistently get a lower result for FC (or higher), your water volume number is suspect, and you may have to adjust it accordingly when you use Pool Math to calculate your chlorine dose.
 
AvM said:
Thanks!
Some more questions:
1) I accidentally raised the fc much higher (32 instead of 20 - I counted my 2.5 gal can as 1 gal) - do I do anything different or just wait till it goes below shock level to add more chlorine?
2) I cleaned the filter last week - If there's some new algae there (the pressure hasn't gone up yet) can that reinfect the pool?
3) Is the oclt performed with fc at shock level?
Click to expand...

1) Yes, just wait and watch as it drops to your SLAM level and maintain that level. Just keep it at your SLAM level and not much higher. Extra chlorine just gets wasted then.
2) No need yet if your gauge hasn't risen 20-25%. And lets be sure that when your pump is off, your gauge goes to zero, right??
3) The OCLT is performed when the water is clear and your CCs are <0.5. It doesn't have to be at SLAM level at all, but I personally would find it easier to determine a loss if it were at a level higher than my normal daily level. I like to recommend about 10ppm FC as a good starting level.

Maddie :flower:
 
Re: 2-Pool water with elevated chlorine, as in a SLAM, is circulating through the filter. It will kill any algae there or in the pool. Just watch the pressure because *dead* algae will be collecting in it.
 
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