Ready to fill it with dirt and start a garden

[jblizzle]

In addition to the loss from killing organics, there will be some percentage of loss during the day to UV. As a percentage, the UV loss is greater at higher FC levels, so more of the higher levels are wasted during the day. I doubt that the higher levels are physically hurting anything, since this isn't a vinyl or fiberglass pool, but it would probably be best to stay around the shock/mustard shock level, from an economy POV.

My pool (salt) has a CYA of around 60. I see on the CYA/Chlorine chart that the shock level is 30. Is there a different level for mustard algae or is 30 what I should be shooting for? Over the past couple of days I have been trying to keep the FC level in the upper 40's (just to hit it hard) and it takes over two gallons of chlorine a day to do this. Yesterday, I started the day at FC 39 and added chlorine (almost 3 gallons) throughout the day. It went up to as high as 51, but dropped back down to 41 by this morning.

From the CYA/chlorine chart in Pool School, with a CYA of 60, the shock level is FC of 24ppm {30 is for CYA of 80}.

According to poolcalculator.com, with a CYA of 60, the shock level is FC of 18ppm with a Mustard shock level of 34ppm.

The pool school chart is a little more aggressive for normal shock levels, but does not indicate anything for Mustard shock level.

In any case, there is no source that is recommending going much over 34ppm and as previously indicated, you will see more UV loss the higher FC levels you attempt to maintain.

 

[izjay]

So... I just tested my CYA 3 different times with two different bottles (one new, one older) of the testing solution. All three tests came in at between 30 and 40. It was above 60 just 3 days ago. I just tested for ammonia and that test registered zero. I always get zero when I test for ammonia and I never show any combined chlorine. I don't want to put anymore CYA in my pool since it just seems to get eaten up by something. I have added CYA at least three times in the last 3 months or so and it never wants to stay above 50. My water is crystal clear, but both chlorine and CYA are being consumed by my pool. Any ideas? Is it time for me to drain this sucker?

 

[Ohm_Boy]

That CYA loss is exactly why I asked earlier if you had an auto-fill device. But since the answer is "no", I am officially out of talent as to why the CYA is dropping.

 

[chem geek]

If that orange/brown film you saw earlier felt slimy, then it could be biofilm formed from when the pool was not properly maintained in the past. As for CYA, it can get oxidized by chlorine, but that's usually very slow and requires very high chlorine and high pH to happen more rapidly. The rapid conversion that occurs from bacteria needs them to survive so normally that means zero chlorine levels, but if the biofilms are thick and well established then I suppose they might be consuming CYA in the interior though that seems unlikely. If you truly have a biofilm problem and if you are impatient with having high chlorine levels ultimately get rid of it (since if it is well established that can take quite a while to break down), then there is another alternative we rarely suggest but did help at least one forum user when they had an unusual biofilm problem. However, it sounded like you already tried that since it's AquaFinesse assuming you used their pool tablet.

Draining and refilling may not fix this problem if it's due to extensive biofilms in piping. By the way, have you checked your filter? Maybe you have a lot of organics in your filter that are consuming chlorine.

 

[izjay]

If that orange/brown film you saw earlier felt slimy, then it could be biofilm formed from when the pool was not properly maintained in the past. As for CYA, it can get oxidized by chlorine, but that's usually very slow and requires very high chlorine and high pH to happen more rapidly. The rapid conversion that occurs from bacteria needs them to survive so normally that means zero chlorine levels, but if the biofilms are thick and well established then I suppose they might be consuming CYA in the interior though that seems unlikely. If you truly have a biofilm problem and if you are impatient with having high chlorine levels ultimately get rid of it (since if it is well established that can take quite a while to break down), then there is another alternative we rarely suggest but did help at least one forum user when they had an unusual biofilm problem. However, it sounded like you already tried that since it's AquaFinesse assuming you used their pool tablet.

Draining and refilling may not fix this problem if it's due to extensive biofilms in piping. By the way, have you checked your filter? Maybe you have a lot of organics in your filter that are consuming chlorine.

I have continued to use the Aquafinesse while I have been shocking the pool. Supposedly it has noticeable effects after 4 weeks and I just passed the 4 week point. Maybe it is possible that it is loosening up the biofilm (if I actually do have this). I have to admit that I am skeptical about this whole biofilm issue in a pool. Should I add more CYA or should I just keep shocking and see if it eventually helps. What is the lowest CYA that I should maintain while shocking? I just switched out my filter cartridge two days ago. I have two fairly new cartridges that I swap out/clean on a weekly basis. Thanks.

 

[jblizzle]

You can shock at 0 CYA, but the sun will consume your FC. As long as you stay above 20-30 for some protection, I would continue to shock (at the now lower required levels). After the shocking is complete, then bump the CYA back up.

 

[carlscan26]

As for CYA, it can get oxidized by chlorine, but that's usually very slow and requires very high chlorine and high pH to happen more rapidly.

He has been shocking at around 2X the recommended levels for his CYA...

 

[chem geek]

He has been shocking at around 2X the recommended levels for his CYA...

Yes, but he saw a drop in a matter of days while normal degradation rates are around 2-3 ppm per month so even at 2x shock level and at higher pH it might be at 1-2 ppm CYA loss per day, not 20-30 over 3 days.

If the FC were lowered to the normal shock level, so at 30-40 ppm CYA that would be more like 12-16 ppm FC or so, then if the chlorine holds overnight with <= 1 pm FC, then shocking can be stopped since the water is clear and there is <= 0.5 ppm CC.

 

[izjay]

He has been shocking at around 2X the recommended levels for his CYA...

Yes, but he saw a drop in a matter of days while normal degradation rates are around 2-3 ppm per month so even at 2x shock level and at higher pH it might be at 1-2 ppm CYA loss per day, not 20-30 over 3 days.

If the FC were lowered to the normal shock level, so at 30-40 ppm CYA that would be more like 12-16 ppm FC or so, then if the chlorine holds overnight with <= 1 pm FC, then shocking can be stopped since the water is clear and there is <= 0.5 ppm CC.

My FC only dropped from around 34 to around 32 last night (7 pm to 7 am). This is the least amount of drop I have seen so far. I am going to let it keep dropping until it gets to the 12-16 range and see if she holds there. I won't mess with the CYA until I see less than 1 ppm FC drop overnight. Hopefully I am turning the corner...

I also have a question regarding oxidation. Does this process ever produce bubbles? During the time when I was seeing the large drops, I was seeing small bubbles come out of my return jets and they formed small bubbles at the surface for a short period of time. I do not see any air in my pump (through the clear cover over the basket) and I am fairly sure there are no leaks in the return lines since I do not lose water. I am just curious if it is possible that the bubbles are caused by the funk being oxidized in my pipes. I just looked and there isn't any bubbles coming out of the return jets.

 

[carlscan26]

He has been shocking at around 2X the recommended levels for his CYA...

Yes, but he saw a drop in a matter of days while normal degradation rates are around 2-3 ppm per month so even at 2x shock level and at higher pH it might be at 1-2 ppm CYA loss per day, not 20-30 over 3 days.

If the FC were lowered to the normal shock level, so at 30-40 ppm CYA that would be more like 12-16 ppm FC or so, then if the chlorine holds overnight with <= 1 pm FC, then shocking can be stopped since the water is clear and there is <= 0.5 ppm CC.

Could there be bacteria in his pipes then that's eating up the CYA?

 

[izjay]

Last night was the first night in a week and a half that my FC dropped by less than 1 ppm. The crazy thing is that my CYA dropped even further to below 30. So, my CYA has gone from over 60 to below 30 in 5 days. There has not been any rain and I have not refilled my pool at all. Hopefully whatever is eating my CYA is finally getting knocked out. I think I will keep my FC (currently at 20 ppm) high for a couple of days just to be safe. I am afraid to add CYA since it may feed whatever the heck is in my pool.

 

[chem geek]

I don't know why your CYA is dropping so much so fast. 30 ppm CYA won't be enough in Florida sun which will become quite intense in summer. You'll eventually need at least 50 ppm and some people go higher than that in hot sunny climates (but not above 80 ppm).

Why don't you just see what sort of daytime FC drop you have at the lower CYA. If it's acceptable now (say, 2-3 ppm over 24 hours), then you can keep up your FC to try and get rid of whatever is left in the pipes that is causing these problems (IF that is the cause). At some point, your FC usage should return to normal and your CYA should become stable.

Yours is a truly unique situation. We've never seen CYA drop like this before this quickly in the presence of chlorine (some have reported some drops over months, but not days). We've seen it drop quickly when the FC is zero, as happened to me, but not when chlorine is present. It does seem like that might be due to biofilms able to survive in the presence of chlorine yet also able to consume CYA. Normally, though, the consumption of CYA creates a huge chlorine demand if the bacteria convert the CYA into ammonia; if they convert it all the way to nitrogen gas, then there won't be a chlorine demand. Perhaps that is what is happening since you reported seeing bubbles coming out of the returns. It's just surprising to have such a huge bacterial conversion going on, especially just in pipes. Normally one only sees this sort of thing in commercial sand filters that can get channeling and significant biofilms.

I'm sorry your situation is so unique. That makes it harder to figure out and solve more readily.

 

[izjay]

I don't know why your CYA is dropping so much so fast. 30 ppm CYA won't be enough in Florida sun which will become quite intense in summer. You'll eventually need at least 50 ppm and some people go higher than that in hot sunny climates (but not above 80 ppm).

Why don't you just see what sort of daytime FC drop you have at the lower CYA. If it's acceptable now (say, 2-3 ppm over 24 hours), then you can keep up your FC to try and get rid of whatever is left in the pipes that is causing these problems (IF that is the cause). At some point, your FC usage should return to normal and your CYA should become stable.

Yours is a truly unique situation. We've never seen CYA drop like this before this quickly in the presence of chlorine (some have reported some drops over months, but not days). We've seen it drop quickly when the FC is zero, as happened to me, but not when chlorine is present. It does seem like that might be due to biofilms able to survive in the presence of chlorine yet also able to consume CYA. Normally, though, the consumption of CYA creates a huge chlorine demand if the bacteria convert the CYA into ammonia; if they convert it all the way to nitrogen gas, then there won't be a chlorine demand. Perhaps that is what is happening since you reported seeing bubbles coming out of the returns. It's just surprising to have such a huge bacterial conversion going on, especially just in pipes. Normally one only sees this sort of thing in commercial sand filters that can get channeling and significant biofilms.

I'm sorry your situation is so unique. That makes it harder to figure out and solve more readily.

Sounds like a plan. I will let you know how it goes. I am continuing to use that AquaFinesse stuff and I actually doubled up on it during the time I saw the big CYA drop. I wonder if it loosened up the biofilm and the bacteria went nuts on the CYA. I have a feeling my problem (if it really is biofilm) is due to me running my SWG real low (less than 1 ppm) over a couple years. My ozonator was keeping the water clear at this FC level except for a couple of algae issues over the years. Maybe the low chlorine level was allowing bacteria to grow big time in the pipes even though the water was clear. I also keep my pool heated around 90 in the wintertime, so there weren't any times when the water got real cold. No need to say sorry. You and others on this site have been a tremendous help. I now know more than I care to know about pool maintenance.

 

[Ohm_Boy]

Any chance that AquaFinesse is somehow taking the CYA down?

 

[izjay]

Any chance that AquaFinesse is somehow taking the CYA down?

Good question. I have no idea... not sure what is in it.

 

[chem geek]

The AquaFinesseâ„¢ Pool Water Tablets MSDS says it contains sodium carbonate (pH Up), sodium silicate (and aid to coagulation), and "sulfuric acid, aluminum potassium salt (2:1:1), dodecahydrate" (aka potash alum which with higher pH forms alum floc) so shouldn't affect CYA levels (unless you used a heck of a lot and they ended up precipitating some CYA out). Of course, if it did, we'd have a CYA reducer which would be very useful to those with high CYA.

 

[izjay]

The AquaFinesseâ„¢ Pool Water Tablets MSDS says it contains sodium carbonate (pH Up), sodium silicate (and aid to coagulation), and "sulfuric acid, aluminum potassium salt (2:1:1), dodecahydrate" (aka potash alum which with higher pH forms alum floc) so shouldn't affect CYA levels (unless you used a heck of a lot and they ended up precipitating some CYA out). Of course, if it did, we'd have a CYA reducer which would be very useful to those with high CYA.

Thanks for the info. My FC dropped 3-4 ppm last night (10 pm to 7:00 am). During the day yesterday my FC dropped about 7 ppm. And, that was with my SWG running. The only thing different about yesterday was that I put a double dose of the Aquafinesse in the pool in the morning (my FC held the night before). I am going to keep my FC at 15-20 until I see it hold overnight again. If it does, I am going to put another double dose of Aquafinesse in and see if my FC goes haywire again. The only thing I can guess is that my plumbing is still all mucked up and the AF is loosening up the biofilm. I am really at my wits end at this point. My wife is about to send me to the funny farm.

 

[duraleigh]

Good question. I have no idea... not sure what is in it.

One of the most important things BBB emphasizes is to NEVER put something into your pool when you don't know what it is or what the effect will be.

Sticking with accurate dosages and precise testing of the simple ingredients (like chlorine) always leads to predictable results and prevents inadvertent side effects.

 

[izjay]

Good question. I have no idea... not sure what is in it.

One of the most important things BBB emphasizes is to NEVER put something into your pool when you don't know what it is or what the effect will be.

Sticking with accurate dosages and precise testing of the simple ingredients (like chlorine) always leads to predictable results and prevents inadvertent side effects.

I completely agree with you and what you said is what I was trying before. I shocked my pool properly several times and ended up with the 1 ppm FC drop overnight. But, when I brought my FC back to normal levels (even higher than normal) my pool would eat up chlorine. And, it has gotten worse over the past few months. I appear to have the one in a million problem that nobody else has seen. That is the only reason I introduced another variable. I plan on going back to the basics if/when I get things straightened out.

 

[izjay]

So, I just spoke with the guy that built my pool and he also maintains pools. I told him about my problem a while back. I got the impression that he thought I was crazy. He just told me that he has a bunch of pools that are having the same problem with chlorine levels not holding and CYA disappearing. He thinks it may be an issue with stabilizer manufactured in China. He said that he noticed the stuff he has been ordering in bulk that is made in china has a funky smell. I have no idea if this is really true, but I figured I would pass it on. We had a huge problem with Chinese drywall down here in South Florida not too long ago, so I wouldn't be surprised if he is on to something.