Free Chlorine Level at 0

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Umarethani

Active member
Jun 4, 2021
40
Suffolk county New York
Hi all.

Love this community and am very much in need of help.

So I've added about 7 gallons of liquid chlorine (10 percent) over the past week but my FC level is constantly showing a level of 0.05-0.11. My CYA level is 0 but I don't know if there is a correlation.

So my question is why is my FC level so level even though I've thrown in about 7 gallons (1-2 every day).

Also there seems to definitely be some dirt near the shallow side and just a little bit of algae maybe near the deep end but water still looks clear. Just a little tough to see the floor

What do I do???

Appreciate any and all help :)
 
You may have ammonia in the water. To find out for sure, don't add any CYA yet. Add enough liquid chlorine to raise FC to 10ppm and test in 15 to 20 minutes. If it's 3 or less, repeat the process, until the FC starts to hold (above 7). This tells you that yes, their is ammonia and when it finally holds, the FC has killed it off. Once it holds, then add enough stabilizer to get CYA to 30ppm and perform a SLAM.

You can use Pool Math website at bottom of this page to enter your gallons of your pool and it will tell you how much liquid chlorine you'll need once you enter the strength (10% or 12.5%).
 
You have a couple of steps to follow in order first:

1. Figure out if you have Ammonia. Raise your pool to 10ppm, wait half an hour, and test your water to see if you still have the FC. If you do, then there is no (or no more) ammonia. If the FC is all gone, then you need to post here again and someone more "expertly" can advise you. But I think you will just have to battle the Ammonia with lots of Chlorine until it's gone.

2. Once you've done that, add enough stabilizer to get to CYA 30. (Btw, how do you know your CYA is 0? k-2006 or TF-100 test kit? Or pool store? It's never a great idea to add stuff to your pool using pool store advice or testing)

3. When you have the 30ppm stabilizer in, you can begin your SLAM to kill off the algae that is starting to form.
 
To get FC up to 10ppm in your pool, you'll need 4 gallons of 10% liquid chlorine. If there is a lot of ammonia, you may have to do this a few times. Ammonia eats chlorine fast as well. Eventually the chlorine will overwhelm the ammonia and kill it off. That happens when the FC starts holding like previously mentioned. Then you can add your CYA to get up to 30 and then SLAM away with liquid chlorine only. You might need quite a bit, so stock up in advance so you don't get derailed once your SLAM starts.

And, yes, once you add the CYA take the FC up to SLAM level which would be 12ppm for a CYA of 30 and keep it there by testing the FC every couple of hours initially if possible. Add enough to get it back to 12 every time, and don't forget to also brush the walls and floor to break up anything that might be trying to grow.
 
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Dan Morrill said:
You have a couple of steps to follow in order first:

1. Figure out if you have Ammonia. Raise your pool to 10ppm, wait half an hour, and test your water to see if you still have the FC. If you do, then there is no (or no more) ammonia. If the FC is all gone, then you need to post here again and someone more "expertly" can advise you. But I think you will just have to battle the Ammonia with lots of Chlorine until it's gone.

2. Once you've done that, add enough stabilizer to get to CYA 30. (Btw, how do you know your CYA is 0? k-2006 or TF-100 test kit? Or pool store? It's never a great idea to add stuff to your pool using pool store advice or testing)

3. When you have the 30ppm stabilizer in, you can begin your SLAM to kill off the algae that is starting to form.
Click to expand...
Tysm!
 
You both are awesome
So I just put in the 4 gallons of 10 percent. I checked after 15 mins just now and FC level is up now (around 7ish). Will check again in 15 mins.
Right now cause its the evening, would it be okay to add the CYA tmrow in the afternoon afterwork? If its okay do I slam the pool right after or should i check the CYA levels in 24-48 hours and see if its up to 30?

Lastly, SLAMMING the pool is just me adding mad loads of lq chlorine. Could you give a rough estimate for how many gallons you think this would be?

THANK U SO MUCH
 
If it does hold the 7ppm FC then get the CYA into the pool with granular via the sock method in front of a return. Keep pump going and slam away assuming it's 30ppm CYA. Not necessary to wait to check assuming your calculations were right.
 

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Umarethani said:
UPDATE :
FC level is same (7ish)
Add the CYA right now, right now? And then dump the liquid chlorine in right now as well?
OR
Can I wait till tmrow afternoon or wud it be too late?
Click to expand...

wireform said:
If it does hold the 7ppm FC then get the CYA into the pool with granular via the sock method in front of a return. Keep pump going and slam away assuming it's 30ppm CYA. Not necessary to wait to check assuming your calculations were right.
Click to expand...
 
You can do the CYA now for 30ppm which is approximately 10lbs granular. Split it up with all the returns because you can't put 10lbs in one sock.. Let it work itself through the night with pump running and start slamming tomorrow. Make sure you get the PH down to 7.2 before you begin slam.
 
If you want to wait, you can. It could mean algae can take hold and you’ll have to work a bit harder or nothing bad could happen. It’s random.
 
DeanP66 mentioned at the bottom of the page Old PoolMath Webpage you can plug all your numbers in and it will tell/suggest quantities of chemicals to achieve the slam. Also you can use it for your daily maintenance. I have the app on my phone that works very well.
 
Umarethani said:
Do you guys have an estimate of how many gallons of bleach (10 percent) I would need for the SLAM?
And afterwards do I just put in a gallon a week?
Click to expand...
It doesn't work this way. You have to check the FC level and bring it up to slam so if you were at FC 7ppm then raising it to a slam of 12 would take 2 gallons of 10%. What I'm saying is nobody can give you the figures. As you go along you test then plug in the numbers to poolmath and it will calculate from there. Tomorrow before you slam measure the FC level and fill the gap for the slam process.
 
The amount of liquid chlorine you'll need will depend on how much algae your pool has. I would start with 15 gallons of 10% to be safe. It takes you 4 full gallons to go from FC 0 to FC 10, so each gallon will give you 2.5 ppm increase. Once you are done with the SLAM (after passing the 3 criteria), you'll let your FC drift down for a day or two until it drops to around 7ppm. Then you will maintain your chlorine level by testing your water and determining how much you need to add to get back to 7ppm DAILY. Just understand that a clean pool with no algae will burn 2 to 4ppm of FC daily, so you have to replenish it. There are some variances depending on how much sun the pool gets, how much foliage it gets and also how many swimmers it hosts (bather load).

Depending on how severe the weather is in your location, you might decide to bump up your CYA to 40 or even 50ppm to slow down the FC burn off. You'll have to raise your FC target level a bit, but the chlorine will last longer with more CYA. Don't go above 50 though and stick with liquid chlorine only. Don't use any tablets or granular chlorine because they will add to your CYA each and every time you use them. Once CYA is in the water, the only practical way to lower its level is a partial or full drain and refill, so stick with liquid chlorine only, because it does not contain any CYA in it.

With your size pool (40k), you'll be using at least a gallon a day to replenish your FC loss. A little higher CYA level (40 or 50) could cut that down a little.
 

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