CYA of 50 & daily additions of 60 oz. or 4 ppm based on my pool

[Catanzaro]

BobbyR:

No, I do not see any grey fluff on the steps or ladder. Only during pollen season, after the filter was shut off did I see in the morning some stuff on the water surface (hard to tell). Each morning, around 6:30 a.m. as I stare at the water, there is nothing on the surface besides a few bugs floating around.

My guess is that the liquid chlorine has degraded. The white boxes were purchased 1 week after I opened the pool. The brown box was purchased approximately 30 days later. I stocked up for the whole summer. Chem Geek states that after 231 days, 12.5% will degrade to about half of its life. A 25% margin error would mean my bleach has degraded to 9.375%, which could mean that the old bleach was sitting around for some time. This could be a possible cause along with having more gallons then what I was told. With 14,700 gallons and to increase your FC from 4 to 7 with a concentration of 9.35%, you would need exactly 60 oz. The numbers make sense, but is this the answer?

I opened the pool on Sunday, April 26th, 2015 and tested the water after 2 hours of running time (12 p.m.). The FC reading was 2. Added 1 gallon of 12.5% that was purchased at Leslie’s nearby. This would have raised my FC to 9.5 on that day. Monday, the 27th, the next morning I tested 8.5 FC, 0 CC. The temperatures were 68, 65, 68, and 75, for the 4 days that this testing started. I added no more liquid chlorine and tested on Thursday (day 4) and had a reading of 5 and CC of 0. The next day I was at 4 and the temperature was 56 degrees on that day. Then I started adding approximately 30 oz. for the next few days and I even lowered the amount to 15 oz. for about 5 more days. After this, I started adding 60 oz. of 12.5%.

As you can see, the chlorine demand was very low in the beginning. When pollen was falling from the sky, and heavy for that month, I had to increase the amount of liquid chlorine to about 60 oz. daily. I am following the TFPC method protocol to a T. This evening, I will start the OCLT test to determine if all 3 areas are passed. I will even test the water before I leave today (around 12:30 p.m.), then when I return at around 6 p.m. and then at around 10 p.m. And yes, I have plenty of reagent's. The drops must be good because they only have been around for 12 months.

 

[chem geek]

As shown in this post, 12.5% chlorinating liquid will degrade over time, especially at higher temperatures. If it was produced in July of 2014, then it's been nearly a year later. Even stored at 70ºF, after 6 months it would likely degrade to 7.8% so after a year it would be even lower. You should NOT stock up on 12.5% chlorinating liquid. It is a perishable item.

So that explains at least part of the problem which is why your FC does not rise as much as expected when adding chlorinating liquid. It does not, however, explain the 24-hour FC loss IF you are measuring FC start and end rather than just assuming the FC at the start based on chlorine addition.

You mention pollen and that could account for higher chlorine demand so perhaps the 3 ppm FC over 24 hours has 1 ppm of it due to the pollen. So your demand may be normal for your pool. If you have pollen, then a skimmer sock is an easy way to collect a lot of it.

 

[Catanzaro]

I actually have skimmer socks and purchased extra baskets and socks. Each morning I swap out the baskets. I like the idea of the pollen being caught in the sock.

I carried forward some results, with an average temperature today until this evening of 83 degrees.

At 7:45 a.m., I added 18 drops for a FC reading of 9, and a CC reading of 0.

At 12 p.m., 17 drops for a FC reading of 8.5, again with a CC reading of 0. The morning hours (total 4) had a drop of .5 FC.

At 6 p.m., 13 drops for a FC reading of 6.5, again with a CC reading of 0. The 6 hours in the afternoon had a drop of 2 FC. The 6 hours had the strongest temperatures throughout the day.

My next test will be at 9 p.m. with a 25 ml. sample. Will post results later. Maybe there is something going on (not sure). Maybe this is just the behavior of this pool.

At 9 p.m., I used a 25 ml sample and counted 34 drops, multiplied by .2 to get 6.8 FC. Did not test for CC as I was using a 25 ml. sample. Ironically this is higher then before, but more precise or accurate. it appears that there was not that much loss from 6 p.m. until 9 p.m. It looks like there was a 2 ppm loss during the day, or over 14 hours. I even vacuumed the pool as well and clean out the skimmer basket-sock. Vacuumed floor and walls. Filter is running all night and next test will be at approximately 6 a.m.

 

[chem geek]

OK, so far so good. 2 ppm FC during the day is pretty common. I suspect your overnight might be at 0.5 ppm FC or a little more and if it's higher with the pump running then before then I'll bet it's just the pollen giving you around 1 ppm FC extra chlorine demand per 24 hours. Nothing to worry about, just note that this is your baseline this time of year. The downside to the skimmer socks is that there will be flow of water with fresh chlorine through the pollen when the pump is running so more chlorine usage than if the pollen were sitting in one place in the pool away from circulation. Of course, the plus side is that you are able to more easily remove the pollen since if it built up you'd eventually have even higher chorine demand than you do now.

 

[Catanzaro]

OK, so far so good. 2 ppm FC during the day is pretty common. I suspect your overnight might be at 0.5 ppm FC or a little more and if it's higher with the pump running then before then I'll bet it's just the pollen giving you around 1 ppm FC extra chlorine demand per 24 hours. Nothing to worry about, just note that this is your baseline this time of year. The downside to the skimmer socks is that there will be flow of water with fresh chlorine through the pollen when the pump is running so more chlorine usage than if the pollen were sitting in one place in the pool away from circulation. Of course, the plus side is that you are able to more easily remove the pollen since if it built up you'd eventually have even higher chorine demand than you do now.

Chem Geek:

Please accept my apology as I am slightly confused on the skimmer socks. Now, the pollen accumulation is not like it used to be. A few weeks ago, the filter sock had to be cleaned each morning and rinsed out. A lot of pollen.

Am I better off with the socks or without the socks? I like the idea of catching debris, including pollen before it gets to the sand filter. Or should I be doing something different. There are 2 main drains, 2 skimmers, and 8 returns, 6 of them spin 360 degrees (octal circulation) & 2 " plumbing. The water moves very quickly.

Also, how do I test for CC with a 25 ml. sample?

My interpretation is that its a catch 22. If I remove the pollen daily, is this best? Or should I allow the pollen to get trapped in the filter? Please advise.

I will know better tomorrow when I test the water. Is it possible that the 10 ml. sample is somehow throwing me off? Maybe it is how I am squeezing the bottle. It appears that some drops are larger then other, which could cause some error. One thing I do know is that the pool water is crystal clear, and I am happy with my results. To be slightly higher than normal makes me feel more comfortable knowing how clean the pool is. The good news is that my 13 year old said last week that the pool she was swimming in did not look clean and the water smelled funny. I guess she is picking up on the TFP method

 

[n240sxguy]

She's now infected with sparklypoolitis. On the cc test at 25ml it's my understanding that 5 drops of the r-003 is still added, I don't think you add more, but the cc reading is done the same as with the 10ml sample. You just multiply by .2 instead of .5 just like the fc test.


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[chem geek]

It is a catch-22 (I was going to say something similar to darned if you do, darned if you don't, but d-a-m-n-e-d is apparently considered to be a curse word on this forum). The convenience of collecting pollen in the skimmer socks probably outweighs the downside of that creating more chlorine demand. If you change or clean out the skimmer sock more frequently during the time when there's lots of pollen, then that would reduce the chlorine demand. If you instead let the pollen get into the filter, the slower flow rate through the filter would probably have lower chlorine demand than the skimmer socks, but be less convenient since you'd have to backwash and waste more water.

You don't really have a terribly high chlorine demand so I wouldn't worry about it.

For 25 ml sample size testing you use a heaping spoon of DPD (or two level spoons), do the FC test as normal (it will use a lot of FAS reagent) where each drop represents 0.2 ppm, then when the sample is colorless you add 5 drops of R-0003 as usual and then add and count the FAS drops until the sample turns colorless again and multiply that latter number of drops by 0.2 (or divide by 5) to get ppm CC.

All the drops in the test should look the same size. Hold the bottle vertical. Wipe the dropper tip with a damp cloth if you suspect static electricity.

 

[wrems]

You guys are hitting on a topic that I've been contemplating lately. It has to do with chlorine demand and the junk that gets filtered...

So, over the course of a couple of weeks I have my sand filter processing about 5 hours a day on average. During that time a lot of junk gets trapped and I run the vacuum around and suck up all kinds of spiders, worms, leaves, you name it. Because the filter is still part of the closed loop why is it ok for the stuff to just hang out in the filter and not continue to cause overall problems vs just leaving the stuff on the floor of the pool? It seems like a consolidation but if it's not removed from the loop one would think that the FC demand would continue to increase? Unless, the pressure inside the sand filter pulverizes the stuff???

 

[chem geek]

The flow rate through the sand filter on a per area basis is rather slow (though not as slow as through a cartridge filter). So while the organics may be exposed to more chlorine than if they sit at the bottom of the pool, it's not as much exposure as if they were in the skimmer. Of course, you can always backwash after cleaning up a bunch of junk into the filter. The ideal scenario is for anything getting into the pool to be collected and removed from the pool and circulation as soon as possible, but we don't live in that ideal world.

 

[Catanzaro]

HERE ARE THE FINAL RESULTS (Carried Forward for Simplicity)

At 7:45 a.m., I added 18 drops for a FC reading of 9, and a CC reading of 0. 10 ml. Sample

At 12 p.m., 17 drops for a FC reading of 8.5, again with a CC reading of 0. The morning hours (total 4) had a drop of .5 FC. 10 ml. Sample.

At 6 p.m., 13 drops for a FC reading of 6.5, again with a CC reading of 0. The 6 hours in the afternoon had a drop of 2 FC. The 6 hours had the strongest temperatures throughout the day. 10 ml. Sample.

At 9 p.m., I used a 25 ml sample and counted 34 drops, multiplied by .2 to get 6.8 FC.

At 6:45 a.m., I used a 25 ml sample and counted 29 drops, multiplied by .2 to get 5.8 FC. The CC is 0. I should have tested at 5:00 a.m., as it was daylight. It appears that I have lost 3 ppm for the day & not 4 ppm as suspected previously.

There will be one more extended test in where I will be adding the 12.5% liquid chlorine to determine how much of an increase I have. The test will be 45 minutes later at 7:30 a.m.

It appears that after adding 60 oz. of 12.5%, the increase was only 2.5 ppm, which in turn means the liquid chlorine has degraded almost by 35%, if not more. Hard to tell as sun has been out and already has been shining on pool for about 2.5 hours. I will be calling the manufacturer today and hopefully getting a straight answer. The good news is that I am on the last few gallons (for this week) and then there is another set which was delivered as we arrived. Luckily, I received a huge discount. The other gallons were produced in March of 2015, stored in basement and in a dark place. I should have better success with that batch.

Thanks everyone for their help. It appears that the liquid chlorine is the culprit and not anything else and the amount of gallons in the pool is pretty accurate.

 

[Catanzaro]

Wow, I finally looked at your spreadsheet. It is amazing how quickly liquid chlorine degrades.

Now the $1 Million dollar question. Do 3" tablets degrade the same way when bound with stabilizer as compared to liquid chlorine? Just curious while we are on this topic.

What I am really asking is if 3" tablets loose the amount of available chlorine over time just like liquid chlorine? I understand the side effects?

 

[JVTrain]

No. Trichlor tablets are chlorine stabilized with cyanuric acid. As long as the tablets are kept dry, they'll last for a long time. Same with cal-hypo powder and dichlor powder. Solid forms of chlorine last a long time and are very convenient. However, using them for a long period of will add things that build up in your pool.

 

[chem geek]

It's the hypochlorous acid in concentrated solutions that is what degrades thermally, chemically reacting with itself primarily as follows (I show two steps combined since two hypochlorous acid form chloride and chlorite and then hypochlorous acid converts the chlorite to chlorate):

3HOCl ---> 3H⁺ + 2Cl^- + ClO₃^-
Hypochlorous Acid ---> Hydrogen Ion + Chloride Ion + Chlorate Ion

There is also the following that occurs, but much more slowly unless there are metal ions in the water since they catalyze the reaction:

2HOCl ---> 2H+ + 2Cl- + O₂
Hypochlorous Acid ---> Hydrogen Ion + Chloride Ion + Oxygen Gas

This is why some excess lye is added for greater stability by raising the pH thereby lowering the hypochlorous acid concentration.

This problem does not occur with solid chlorine materials if they are kept dry. If they become moist or wet, then the above degradation can occur though may be somewhat self-limiting as the "solution" gets saturated with cyanuric acid (for Trichlor and Dichlor). This is why you'll find desiccant packs in containers of dry chlorine product. Keeping the product in a cool dry place will have it last for a long time.

 

[sbcpool]

The ideal scenario is for anything getting into the pool to be collected and removed from the pool and circulation as soon as possible, but we don't live in that ideal world.

A little off-topic, but that's why I use one of these:

I just install it over the filter sock and most of it gets caught in the filter sock where I just dump it when I'm done vacuuming.