Chlorine Levels

[chughs]

All,

New member and would appreciate any help. A few weeks ago, we thought we had metal stains and tried to get them out. using local pool store advise, we let chlorine drop to zero and used the metal free etc with associated backwashing etc. Since then we have not been able to get the chlorine levels back up. We have dumped in whole lot of Chlorine over this time, raised the PH which had dropped etc. The current readings are

Free Available Chlorine -0, Total Available Chlorine - 0, pH - 7.4, Total Alkanity 120, cyanuric acid 100, calcium hardness - 140, phosphate - 0, nitrates 5 ppm. A week ago, TC was 2, FC was 0.5 and we had 6.8pH. We live in North East and are running out of ideas. Inground 32000 gallon pool. Pool is clear and looks swimmable. Brown stains still there.....

[PoolGuyNJ]

We need a lot more info about the pool.

A 1.5 ppm of combined chlorine (2 TC - .5 FC) is way too much CC.

100 ppm of CYA is too much, especially in the NE. A 0 ppm TC value means you aren't adding enough frequently enough or you're not using a chlorine elevator.

Scott

[LegsOnEarth]

What are you using to raise your chlorine levels? Are you just throwing some tabs into a floater? Have you been trying to bring it up with Liquid chlorine or granular shock?

Based on your high CC and CYA levels, my assumption would be that you primarily used tablets to chlorinate, and probably didn't shock/hyperchlorinate your pool very much.

Also, if you do have metals present in your water, they may have increased your chlorine demand. What exactly did you use to try and remove the metals/stain? How much did you use?

[chughs]

I used shock to increase the chlorine content. We buy ours from Sams club. I normally drop in a 3 pounds for a 32000 gallon pool. over the last weeks, we must have added in approx 25lbs over 2.5 weeks. Max at any one time was 7 pounds

We also used liquid chlorine last week and put in 3 gallons. We just got Taylor test kit and rechecked. FC was 0, TC was between 1 and 2, and CYA seemed to be 80

Let me know any other information needed

[chughs]

for removing stains, we were asked to use Stain Remover and Metal Free. Also a couple of weeks ago, we were asked to put in stablilzer. Pool is clear, no signs of algae

[jkusmier]

I used shock to increase the chlorine content.

Can you confirm you were using cal-hypo? Sodium dichlor is available in both tabs and a granular form.

[chughs]

It was pool brand , active ingredients are Sodium Dichloro-s-Traizinetrione hydrated -99%, Available chlorine 55%

[chem geek]

So that's Dichlor. For every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases Cyanuric Acid (CYA) by 9 ppm. You just made your already too high CYA problem even worse.

[chughs]

I understand that now. What are my options - if any.

[jkusmier]

You are experiencing a classic case of an over-stabilized pool, meaning that you have oversaturated your pool with cyanuric acid by using a stabilized form of chlorine - sodium dichlor, or simply "dichlor."

Since you have not mentioned having a salt water pool or a chlorine generator ("SWG"), I assume that you have a non-salt pool.

Recommended levels for a salt water pool are 60-80, but for a non-salt pool like yours, you want to aim for 30-50. The only cures to excessive CYA are 1) partial drain/refill of your pool water or 2) overwintering (CYA levels do degrade over the offseason, although I'm not sure anyone has explained the science behind that - Chem Geek?).

It's OK to open the pool with stabilized forms of chlorine, but you have to monitor them afterward and keep them within limits by using unstabilized forms of chlorine, like cal-hypo (can precipitate at higher levels in non-gunite pools, clouding the water), lithium hypo (prohibitively expensive for most), generic unscented bleach (5%) or pool store versions like Vertex (10%) or conversion to a SWG.

The good news is that your problem is easily fixed. The questions are: do you winterize your pool? Do you have a gunite, fiberglass or vinyl-lined pool?

[chughs]

We do winterize our pool. use a local service company. Usually get it done just before leaves start falling. Should be relatively soon. The pool company specs for interior of the pool call it a plaster. Definitely not fiberglass or vinyl.

[chughs]

Guys, Any thoughts...

[chem geek]

Well, removing metal stains involves doing an ascorbic acid treatment, but that has the chlorine level go to zero during the process so you add some Polyquat algaecide to help prevent algae growth. However, the risk of getting algae when the treatment is over is fairly high due to your high CYA, if your pool's high in algae nutrients. So normally one takes care of the high CYA level first by diluting with fresh water. Since you are about to close the pool, it's a tough choice unless you were going to let the pool go over the winter in which case you can just deal with getting rid of algae upon spring opening.

You should probably first absolutely confirm that you've got a metal stain by taking a Vitamin C tablet and putting it (or crushing it and putting the powder) over one part of the stain to see if it removes it. If it does, then add a large dose of Polyquat 60 to the pool (the maximum dose on the label) and then add if your chlorine level is still high then you might want to lower it with chlorine neutralizer or hydrogen peroxide. Then add ascorbic acid. The full procedure is described in this post.

[chughs]

chemgeek,

Wish I had come to this forum before trying the metal treatment. We did have the exact issue of algae growth you warned about. However, we do not have algae growth at present. I also did a test dilution of the pool and got the CYA down to 80.

The main problem I want to solve is chlorine levels, which are stuck at 0.5 levels. If CYA levels are holding that back, and they degrade over winter, then do I wait for opening and then bring the chlorine level up or do I need to fix the chlorine level now.

[LegsOnEarth]

What kind of filter do you have on the system? How old is the water? You said you diluted it recently to bring it from 100ppm cya to 80, or did your retest just yeild different results?

If you have a sand filter, how old is the sand in it?

[chem geek]

Getting the chlorine level up is easy. You just add chlorinating liquid or regular unscented bleach. Use The Pool Calculator to calculate dosages. With a CYA of 80 ppm, you'll want to keep a minimum FC of at least 6 ppm to prevent algae growth. If you are losing more than 1 ppm FC overnight when the sun if off the pool, then you should shock your pool which, due to your high CYA, will need around 30 ppm FC or so to kill off whatever is growing. So first raise the FC to 6 ppm and verify that in the evening and then measure early morning to see your overnight chlorine loss. You can have nascent not-yet-visible algae growth in the pool and that's what we're trying to figure out. If you have that, then you shock the pool to kill it off. If you don't have that, then you should be able to get your FC up and keep it there, using perhaps 2 ppm FC per day to maintain it.

[chughs]

Referred to the pool calculator and it produced a 1992 oz of 6% chlorine to get chlorine upto 30ppm. Got 12 jugs of chlorox and poured them all in last night. Used Taylor test kit to check for FC which is still 0. Pool is clear with no visible algae

[chem geek]

What kind of Taylor test kit are you using? The DPD test can bleach out at high chlorine levels. If you have a plain OTO chlorine test, it won't bleach out. If you have a Taylor K-2006 that uses a FAS-DPD chlorine test, then add more powder since a "flash of pink" would mean that it too is getting bleached out though that usually is only at very high FC higher than you should be seeing now.

If in fact your chlorine is still reading zero, then you've got some large chlorine demand in the pool. Perhaps you used too much ascorbic acid since it will act as a chlorine neutralizer, though I'd be surprised if it would use up 30 ppm FC. The other possibility is that when the FC was 0 that there was a bacterial conversion of CYA into ammonia but that usually won't happen if you had Polyquat 60 in the pool (it sounds like you didn't).

You can see what your chlorine demand is by taking a large bucket of pool water and adding bleach to it until you get a measurable FC. 1/4 teaspoon of 6% bleach in 2 gallons is 10 ppm FC.

[chughs]

Chemgeek,

Checked chlorine demand yesterday. took 2 gallons of pool water, added 3/4 teaspoon of 6% bleach, no fc. then in afresh sample added in a teaspoon - blaze of red. So went down to 7/8 of a teaspoon and still got the same reaction.

so using pool calc got 20 gallons of 6% bleach and added in last night. ran the test again this morning.no measurable FC. diluted the sample with half pool water and half tap water still nothing. using Taylor K-2005. It is a DPD test, though not a powder. it is a liquid. stumped .

[waterbear]

You are using a DPD test so you cannot test FC above about 10 ppm without following the dilution instruction on the lid of your kit in small print in the bottom of the chlorine testing section! Your test is bleaching out! You can easily check by getting an OTO/pH two way test kit at someplace like Walmart. (color comparator uses yellow color blocks) OTO will not bleach out but only tests total chlorine. You should find the color to be off scale and oragne to brown instead of yellow.

You might want to consider adding a Taylor K-1515 to your kit so you have the FAS-DPD chlorine test which is far superior to the DPD test. IT is not a color matching test but a drop counting test with a color change from pink to colorless (much like the TA and CH tests are drop counting tests). It can test FC levels up to about 50 ppm and directly tests CC (instead of testing TC and then needing to subtract the FC from the TC to get the CC. You can find this test kit from several internet retailers such as Amazon and Amato at a decent price. The difference between the K-1515A and the K-1515C is the A has .75 oz of FAS titrant while the C has 4 oz. (and a bigger case to hold the bigger bottles.)

[chem geek]

(you wrote "7/8", but you meant "1/8" I presume). What's weird though is that the pool water sample in the bucket PLUS some bleach shows up in the DPD test while a pool water sample by itself does not. If it was bleaching out with high FC from the pool sample directly, then I'd expect it to still bleach out with the bucket test (which it didn't). When you did the bucket test, did you wait after adding the bleach? Check the bucket again 30 minutes to an hour after adding the bleach. Maybe there is chlorine demand, but it's not immediate. Of course, with a real FAS-DPD test, this would all be so much easier to diagnose properly.

[waterbear]

Of course, with a real FAS-DPD test, this would all be so much easier to diagnose properly.

Or by using an OTO test as a check for bleachout.

[chughs]

Will get the test and recheck chlorine levels. Thanks all for your help and support