No Available Chlorine

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scott802

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Sep 14, 2015
51
Grapevine Texas
Hello and thank you for such a great resource.

I have a 30,000 GAL vinyl in ground pool with an Aquarite T-cell 15 chlorinator. Been trouble free for years except changing cells more often than I would like. I have an issue just recently where my water suddenly turns cloudy and my local pool store testing the water reveals no free available chlorine. I"ve tried everything including shocking the water (they recommended non-chlorine shock which I added 6 lbs of - no change).

The 2 cells I have are testing 'OK' by the pool store although it seems their effectiveness diminishes over time even though the pool store test reads 'CELL OK'.

This summer especially I am having problems keeping the water clear. Also, I have just replaced the entire control board several months ago on the Aquarite since the current limiter tends to crack and fry after a few years in the heat. Everything is calibrated properly and had been working fine.

The only thing that seems to keep my water clear is actually shocking the pool with standard pool shock, which in the past I had NEVER had to do. When I set the Aquarite to 'super chlorinate' typically there would be well over 5ppm of chlorine in the water within 24 hours. not any longer.
Also, I have 2 cells, one cell is just opened out of the box within the last 3 months.

Free Available Chlorine 1
Total Available Chlorine 2.5
Salt 3100
Calcium Hardness 200
CYA 60
Alkalinity 150
PH 7.6
Copper 0
Iron 0
Phosphates 0


Any help would be incredibly appreciated.

Scott
Dallas TX area
 
Hello Scott and welcome to TFP. Cloudiness is an indication that you may have algae beginning to flourish in the water. Your FC level is quite low right now. In addition, you have a CC (combined chlorine) level of 1.5 which exceeds our recommended level of <=.5 ppm which is also an indication algae may be forming. This happens when the FC level gets too low. First, I want to point you to the Pool School - Chlorine / CYA Chart. On this chart (bottom portion for SWG), you'll see that your recommended CYA level is at least 70. That is designed to ensure you have enough stabilizer to protect your free chlorine (FC). Yours looks a little low right now. One that chart, you see that if your CYA is adjusted to 70, then your FC should be 5. When it drops below your target, and especially below your minimum, that's when cloudiness and algae begin to form.
The cloudiness and algae can be resolved by doing a SLAM via Pool School - SLAM - Shock Level And Maintain. Once the SLAM is complete, and you've passed all 3 SLAM criteria, your water will remain algae-free as long as you maintain the proper FC/CYA levels as noted on that chart.

Let us know if you have any more questions on how to proceed.

- - - Updated - - -

Also, please keep in mind that the proper test kit (i.e. TF-100 or Taylor K-2006) is the foundation of your pool care. Why these kits? We've learned through personal experience that you cannot reply on pool store testing, test strips, or simple over-the-counter kits. They simply do not read Free Chlorine (FC) or Cyanuric Acid (CYA) levels accurately or to the high levels we need. If you do not have a TF-100 or Taylor K2006 test kit, it should be your #1 priority.
 
Scott,

One thing to keep in mind is that SWGs are a great way to continually dose water with chlorine. However, they are essentially useless as a source of chlorine for raising a pool to shock levels and killing algae and pathogens that don't make it into the bulk pool water. Once an algae bloom gets going or if bacterial biofilms develop in pipes, then you absolutely have to use liquid chlorine to kill and destroy them.

If your water is clouding up then you very likely allowed the FC to get too low for your CYA value and algae is now growing faster than the SWG can kill it. The only way to correct this situation is to follow the SLAM procedure. Once you get your water clean, then the SWG should be able to keep your water clean.


Sent from my iPhone using Tapatalk
 
One other thing...until you get rid of the pool store testing, there will be no way to tell what is going on in your water. They are wrong more often that they are right and will steer you towards expensive chemicals that you will eventually need to dump down the drain.

This site strongly suggests your own test kit so that you can tell what you need to do. The TF100 or the K 2600 are the two that are the best.
 
In addition to all said above I want to add that your pool *needs* chlorine, not "non-chlorine shock" whatever that was supposed to do? SWGs provide your baseline constant low level of FC, but they can't boost the FC high enough or fast enough to deal with algae outbreaks. Use the liquid then.

You can see if your pool store sells liquid chlorine which is usually 10-12.5% chlorine, or just use common household 8.25% bleach. No matter which you choose to supplement your SWG make sure it is fresh and not stored outside in a garden center or something like that.
 
Thank you all for your expert advice, I have added 3 gallons of liquid chlorine to the water and plenty of CYA but the first thing I need is my own test kit. Leslies Pool Store gives inaccurate test readings as I found out by going to 2 stores and getting completely different results. I'm following the SLAM procedure.
It's unfortunate because I've had this pool for many years trouble free and always relied on the pool store test results never had a problem until now.
Will keep trying
 
A very common occurrence. At least now you know. We still have a few weeks of decent weather, so when your kit arrives, post a new full set of test results and we'll help get you on-track. Please update your pool info so we can advise you properly. For now, while you wait for your test kit, maybe just add one gallon of generic 8.25% (regular) bleach each day. Generic from Wal-Mart or HEB is fine. That's just to hold you over until we can get good numbers.

- - - Updated - - -

Did you order the speed stir as well? If not, make sure you do. It's fantastic and makes the testing process soooo much easier.
 
All,
my TF100 kit finally came. Here are the test results.

CYA = 80
PH = 7.8
TA = 110
Salt = 3800ppm
FC = 1.5
CC = 2.5
TC = 4.0

My water is still not very clear. Once I resolve this problem I am going to need help with the metal staining of my vinyl liner. I keep adding the (expensive) ascorbic acid and it clears it up but it just keeps reoccurring. I never had this staining in past years. I am assuming it is metal stains since the ascorbic acid cleans up the liner immediately. I have tried metal free etc but it keeps coming back. This in and of itself could be contributing to the cloudy water.

Ok, those are my test results above with the TF-100 test kit. Please help!!

Thank you,
 

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Well, the combination of cloudy water and elevated cc reading would indicate to me a SLAM would be in order. That would also explain why your FC keeps dropping so low. First, use acid to lower you pH to about 7.2. The SLAM FC level for a pool with a CYA of 80 is an FC of 31. You will want to turn-off or dial-down your SWG and use just regular bleach from HEB or Wal-Mart - generic is fine to get the FC to 31 and keep it there. Follow everything as noted on the SLAM page (link below) and give it time to work until you pass the 3 SLAM criteria. Make sure to do everything as noted on that page and it will work for you. If you have any questions, please let us know.

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Do the acid first, then wait 30 min before increasing the bleach.
 
Use PoolMath, see my signature. Input your pool specs, what your desired levels are and the strength of chlorine you are using. The result should be 44 ounces of 8.25% bleach to raise the FC by 1ppm.
 
I need some help with the numbers. I used your pool math calculator here is what it said for my 30,000 gallon pool.

my current FC = 1.5, target = 31. In order to achieve this I need to add 1839 oz of 6% bleach? Is that common household bleach you refer to?
1 gallon jug = 128 oz so 1839/128 = 14.3 gallons?????

On the muratic acid to get my ph from 7.8 down to 7.2 it says add 75 oz of muratic acid. I've already added 128 oz 1 gallon so I should be fine.

Before I dump over 14 gallons of bleach into this pool I want to confirm this is correct as it seems like it would make the water a toxic chemical waste dump...

Thanks very much
 
Common household bleach nowadays is typically 8.25% sodium hypochlorite sold in 121oz jugs (not quite a gallon).

If you can, call around to pool stores and see if they carry larger sizes of liquid chlorine (10% or 12.5% sodium hypochlorite). Some stores even sell the LC in refillable containers which will cut down on the recycle trash.

Bleach is fine. Chlorine is chlorine is chlorine as the old saying goes. For a SLAM, you will use A LOT of bleach, so try to find the cheapest source you can.


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I did some modifications to the calculations.
The bleach I'm using is 8% household bleach in a 121 oz jug.

What this calculator tells me is to add 11 121 oz jugs or 1354 oz. of this bleach to get me from a FC of 1.5 to 31.

is the above correct?

Thank you!
 
+1 :)

Most bleach these days is 8.25% So you'll want to check the side of your bottles and adjust Pool Math accordingly. Will be fewer bottles.

As far as the toxic comment; "not at all" Actually, that's kinda what you have now, that's why you need the chlorine. Between whatever is in the water and the CYA, that really isn't as much as it seems like. The algae or whatever you got will neutralize it quite quickly and the CYA acts like a buffer so the effective chlorine is lower then the FC value.

Also, be prepared for the Maintain part of the SLAM. You will be testing and adding more bleach for a little while to come.
 
Yes... it does take a LOT of bleach, especially low % bleach, to reach the SLAM target, especially when your CYA is on the high side. It certainly won't be a toxic waste dump. The strength of the chlorine you're adding is very moderated by the CYA in the pool. By the time you add all the bleach to the pool and get it circulated, most of that chlorine will be bound to CYA in short order. That's why you need so much to attack the algae. Once you get it up to that level it's then easier to maintain the SLAM FC level. At that point, you'll only be losing FC to sunlight and what is being consumed by the algae. If you can find a source of 8.25% bleach or even pool store strengths of 10-12.5% that makes for less jug hauling and disposal.

Did you input your current TA and other levels into Pool Math when calculating your muriatic acid needs to lower pH? pH changes are highly dependent on TA levels so be sure you have those values in and make sure you verify the pH is near 7.2 before adding any bleach to the pool. Once you have those high FC levels, pH cannot be accurately checked as the pH test is invalid above 10 ppm FC.
 
I think the Lowe's liquid chlorine might be a better solution. I know they sell it in large jugs and it's probably higher strength than household bleach as you've all pointed out. So I think I will go that route less jugs less mess.

Will keep all of you posted. Thank you so much for all your expertise!
 

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