Numbers ok but water has a hint of cloudiness

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Catanzaro said:
Maybe someone who has been at this for a while can answer this question. I have been following this thread for a while. Posted this before, but maybe have been overlooked.

Please see below:

Is there a testing error when the FC becomes that high with the TF-100? I believe in the past I read the higher you go on the ladder, the probability of testing error increases. With that being said (if accurate), does it make sense to allow the FC to drop to around 10 and then perform the OCLT test? Please see comment below as I would like understand this better. For me, luckily I found TFP early enough and have never had any issues with passing the overnight test.
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I agree that the OCLT being performed at no more than an 8 hour time frame is a pretty good timeframe where accuracy can be ensured.

From what I have learned, and others may also be able to explain this better for you as well. It is recommended that the OCLT be performed at the Shock level following a SLAM. It is not recommended to allow the FC drop to 10ppm which could in turn allow algae regrowth, or backslide, if the SLAM itself is not fully complete.

There are times If the numbers are being consistently held, yet the Op is teetering on the overnight FC loss just barely enough to prevent passing for several days, and the water is clear, and the cc is 0, that I've seen some have them drop the FC level to test OCLT, but as a rule, due to possibility of reoccurrence from incompleted SLAM, etc. this is not the best, nor suggested way to perform an OCLT following a SLAM. (IMO It is better to be safe than sorry because if the Fc level is allowed to drop before the SLAM is complete this could cause the OP to backslide causing them a lot more time, work, frustration, and chlorine).

I read a really good article on here the other day that I'll try to relocate for you, if I can, that explains that even with the margin of error at the higher shock levels, if the Slam is complete, the overnight FC loss will be 1.0ppm or less, regardless of the FC level the OCLT is being checked at.

I hope this helps to kind of explain why it is recommended that his, and others are needed to remain at shock level until OCLT is passed. Have a nice day.:)
 
Crackerjack4u:

Yes, this explains. Thank you.

It just appears that something is missing, with regards to data, maybe testing. Maybe the size of the drops when counting 70 drops causes some inconsistency. Pressure on the bottle makes a difference. I may be reading into this post too much.

I had to have the light removed by the PB over a complicated issue (in another thread) and behind there was floating algae (in the light niche housing), not a lot, but enough to be considered larger pieces. Some floated out and some probably stayed in there. More often, once would think that algae behind a light niche really is hard to get to. And chances are that you can not brush behind there without removing light and definitely water circulation would be as difficult. I actually moved a rotating head so both sides of the light niche have better water movement for this reason. Maybe this could throw off testing, who knows. Ironically, I perform the normal test each month, where I around 10 p.m., and then at 6.00 a.m. Usually, there is no loss, or less than .3, as I use a 25 ml. sample.

Thank you for your quick response! :)
 
Catanzaro said:
Crackerjack4u:

Yes, this explains. Thank you.

It just appears that something is missing, with regards to data, maybe testing. Maybe the size of the drops when counting 70 drops causes some inconsistency. Pressure on the bottle makes a difference. I may be reading into this post too much.

I had to have the light removed by the PB over a complicated issue (in another thread) and behind there was floating algae (in the light niche housing), not a lot, but enough to be considered larger pieces. Some floated out and some probably stayed in there. More often, once would think that algae behind a light niche really is hard to get to. And chances are that you can not brush behind there without removing light and definitely water circulation would be as difficult. I actually moved a rotating head so both sides of the light niche have better water movement for this reason. Maybe this could throw off testing, who knows. Ironically, I perform the normal test each month, where I around 10 p.m., and then at 6.00 a.m. Usually, there is no loss, or less than .3, as I use a 25 ml. sample.

Thank you for your quick response! :)
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As you mentioned there are several factors that can affect the results as you have described and that too is why those things like ensuring that they are holding the reagents bottle upright, instead of vertical, applying the same amount of pressure etc. are all important reminders should someone be having difficulty with their testing.

Hopefully the rotating head will allow you to get enough circulation around the niche to prevent algae from forming there, allowing you to continue to pass your monthly overnight checks. Have a nice day :).
 
It might be a good idea to add taking the light out on a monthly bases to clean inside the hole. You will need two tools for this-a toothbrush and a turkey baster. The toothbrush to make sure you get the whole are clean. The turkey baster to put 50/50 bleach/water inside it.

There was on member that was _ close to clearing his pool BUT he just could not pass the OCLT. He finally took out his light and.........it was FULL of algae! Once he took it and let it sit on the side of the pool while he held his SLAM for a couple more days he PASSED!

Kim
 
Crackerjack4U and Kimkats:

The floating algae was not on the light (per se), but deep behind the light in the actual housing. It was not a lot of algae, but a few small pieces, not many, maybe a 1" or so. I believe the FC levels at the proper CYA as water always sits there should keep this in check. I am one of the only few people that had to have the light removed within one year over an issue. It is difficult to remove the light each and every time. Although, if I were to fail the OCLT test repeatedly, this is the first place I would have to inspect.

The floating algae was in the plastic housing (e). I actually brush the light and ring often and the light, upon removal had absolutely no algae on the surface or on the light itself.

Pages from DuraNiche-SP060xU.jpg
 
those things like ensuring that they are holding the reagents bottle upright, instead of vertical, applying the same amount of pressure etc.
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Maybe the size of the drops when counting 70 drops causes some inconsistency. Pressure on the bottle makes a difference.
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Not really. Done correctly, all drop testing should be done with the bottle completely inverted and the operator should allow the drops to "fall" off the tip. There should be no pressure to force the drop off the tip......let gravity do it
 
duraleigh said:
Not really. Done correctly, all drop testing should be done with the bottle completely inverted and the operator should allow the drops to "fall" off the tip. There should be no pressure to force the drop off the tip......let gravity do it
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The R-0871, complete inverted for me does nothing (maybe doing something wrong). VERY VERY little pressure effort, the drop gets to the tip and then "falls" off the tip, without pressure, slowly and consistently. Although, I need some pressure. The is a slight time delay between each drop. Any more pressure and the drops fall very quickly.


Thank you for your quick response.
 
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The R-0871, complete inverted for me does nothing (maybe doing something wrong). VERY VERY little pressure effort, the drop gets to the tip and then "falls" off the tip, without pressure, slowly and consistently. Although, I need some pressure. The is a slight time delay between each drop. Any more pressure and the drops fall very quickly.
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You are doing it correctly and we are saying virtually the same thing. Some pressure has to be applied for the drop to form on the tip and then if falls off the tip, not from pressure, but from gravity pulling it off the tip.
 
Gobbler that does seem like a little more of a loss then what you've been having throughout the day, although you're not adding any bleach right now to maintain the higher levels. On average we generally see approx. 2-4ppm FC loss during the day, but I have seen some return to below 10ppm after passing OCLT with a 28-31ppm chlorine level within just a couple days, so in those cases it certainly didn't take long for the levels to drop from shock level to recommended maintain levels.

I'd just continue to monitor it, and if it continues to have larger than expected drops, then it's fine to add enough chlorine to raise, and maintain it back at shock level for another day or so, and you can retest OCLT at that time. But of course, once the sun goes down that will tell you the most accurate story, and give you a better baseline of how much loss you are truly having once the sun depletion factor is taken out of the equation all together. If the FC drops seem to stabilize back out, and slow down tonight, (which I suspect it probably will), then go ahead with the planned repeat OCLT tonight, and in the morning. Keep up the great job, and have a wonderful day :).
 

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Just checked it and it is 33. Think I might check it again before bed and first thing in morn to see what I lost overnight. If none I may let it get back to 5-6 before turning SWG back on.

What will happen if I close the pool down in a week or so and the problem is still here? Will the algae die in cold weather?
 
That's more of what I was expecting the FC to be at. Be very careful on your extra OCLT testing, take your time, so you can ensure both tests are accurate so it doesn't mess you up. Also be sure to check the FC and CC tonight, and in the morning too.

Hopefully you won't have to worry about the algae problem still being there because the way your numbers seem to be doing today, I think you've got it killed out finally. If you close with algae, you reopen with algae and have to resume SLAM at opening. :(. So let's ensure there is no algae still in there at closing time. :) Have a good night Gobbler. I really think tonight's the night that you officially get er done :).
 
Catanzaro said:
Is there a testing error when the FC becomes that high with the TF-100? I believe in the past I read the higher you go on the ladder, the probability of testing error increases. With that being said (if accurate), does it make sense to allow the FC to drop to around 10 and then perform the OCLT test? Please see comment below as I would like understand this better. For me, luckily I found TFP early enough and have never had any issues with passing the overnight test.
Click to expand...

The official accuracy for the Taylor tests, and the TF-100 is based on Taylor reagents, is +/- 1 drop or 10% of the reading whichever is greater. This is for absolute accuracy. The OCLT is more about relative accuracy since one uses the same reagents for measurements at night and in the morning. So it's more about how accurately you can measure the sample size and create consistent drop sizes. You might be able to do better than 10%, but probably not better than 5%. With a 33 ppm FC and a 5% error that would be 1.65 ppm FC error. For sample size, 5% of 10 ml is 0.5 ml which is half way between two lines on the tube when measuring the meniscus. It would be hard to do any better than that. Also, when squeezing the FAS-DPD drops, one would need to create drops that are consistent (on average) within 5%. Actually, both of these would need to be better than 5% for their combined error to be less than 5%.

So you can see that having a 1 ppm FC criteria for OCLT at high FC levels doesn't make sense. This is why it should never be done with a high yellow/mustard algae SLAM and for a regular SLAM it is a questionable criteria when the CYA is higher since the FC would then be higher. If you are very careful with measurements, then at a 33 ppm FC I'd call a 2 ppm FC or lower drop "good" for passing the OCLT, especially if one is bouncing around this sometimes lower or no loss or even gaining in FC (indicative of the limits of testing). If one wants further verification assuming other SLAM criteria are met, then lowering the FC to more normal levels closer to 10 ppm FC (or certainly not higher than 20 ppm) would be reasonable.

Algae should not come back at a half-SLAM level. The worst that could happen is that you find there's still a chlorine demand that has not been exhausted and you need to go back up to try and finish it off.

Crackerjack4u said:
I read a really good article on here the other day that I'll try to relocate for you, if I can, that explains that even with the margin of error at the higher shock levels, if the Slam is complete, the overnight FC loss will be 1.0ppm or less, regardless of the FC level the OCLT is being checked at.
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Where did you read that? It's true you don't want to end a SLAM prematurely, but if the other criteria are met with no visible algae and minimal CC then if the FC drop is low but not meeting the OCLT criteria but within test error, then it should be safe to lower the FC and for reassurance redo the OCLT at a lower FC, particularly if we are talking about SLAM FC levels of 33 ppm as in this case.

It is also not true that the actual (i.e. no measurement error) loss will always be 1 ppm or less regardless of FC level. That is only roughly true for the same FC/CYA ratio, but at a given CYA if you increase the FC level it's overnight loss will increase if for no other reason that the chlorine will oxidize the CYA faster even if there were nothing else in the pool to oxidize. This is again why one should not have a 1 ppm criteria for the yellow/mustard algae SLAM level, for example, since that is 2.3 times higher in active chlorine level and can push chlorine loss from oxidation of CYA to at least 2 ppm over 12 hours or 1.3 over 8 hours.
 
Chem Geek:

Thank you for this post. I recall reading something to this effect a few months back during another post. Have bookmarked for future reference.

In my own personal experience, I know that many small variations in testing could throw off the figures. It just did not make sense, all the variations if everything appeared normal, and the 1 ppm loss was not consistently being maintained in the overnight process. When I repeat a test, sometimes the results will be slightly different, especially with the CH and TA test, which of course is that 10% testing error that I recall.

Sometimes, I will bring my FC level up to 10 ppm (based on my 40 CYA), and not add for a few days. I estimate the 2 ppm loss daily (at most, especially this time of year in NJ) and wait a few days (no more than 3 days), and retest at same time. Then, I average the daily loss. This, in my opinion is easier for me as any testing error cold be averaged. I do this weekly, and calculate, the average over 7 days. Lately, the total loss has been about 1.29, 1.36, as there is no activity. Because the water is clear, my cc is usually 0, I use this type of test instead of the OCLT. One would know, especially this time of year, if I was burning off 3 ppm each day, over a 3 day time span, that there is a problem somewhere. This is never the case as I have been diligent in testing and tracking levels, etc.
 
I say well done, and Congrats Gobbler. YOU DID IT!!! :party::whoot:

Chem Geek, Thank you for the clarification, and the additional information. I will continue to search for the thread because I didn't bookmark it. It was one that I just ran across while searching for additional information. When I locate it again I will let you know, so you can see it. Thank you again for the clarification, and have a wonderful day. :)
 
That sounds wonderful Gobbler.

Just continue to let your FC drop on its own, and as Chem Geek said above in #118 when your FC gets to around "15ppm you can try another OCLT," and you should see the 1ppm or less FC loss that is often not seen with the higher FC levels.

Also when your FC gets below 10ppm, go ahead and do a full set of levels for us, and we'll help you adjust them then before closing should it be needed. :).

Have a wonderful day, and well done Gobbler!!! :)
 

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