Unexplained FC Consumption - SOLVED - although the Mystery Remains

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Re: Unexplained FC Consumption (updated title)

Some more questions -

You always quote dosing in ppm of FC, but I assume your Stenner is set based in volume flow rate. What's your volume flow rate on the Stenner? How much can it deliver and over what time period do you deliver chlorine (slow drip, fast burst, etc)?

Any chance your wife would be willing to learn how to use your chemistry set and get some reliable numbers while you're away? Perhaps you can bribe her with a promise of taking her on your next business trip or buying her some nice jewelry.

Keep us posted on the results.


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Re: Unexplained FC Consumption (updated title)

toofast said:
I don't want to burn all my CYA with access FC
Click to expand...

I've seen this mentioned a couple of times in this thread...where does this theory come from? I've not seen it elsewhere. It seems like if very high FC levels were capable of "burning CYA" to lower the CYA level, that would be a very commonly-prescribed approach on this form. Why drain/fill and then slam when you can just slam at "burn off CYA" level and kill two birds with one stone? That makes me question whether this "CYA burning" is real.
 
Unexplained FC Consumption (updated title)

Vyrolan said:
I've seen this mentioned a couple of times in this thread...where does this theory come from? I've not seen it elsewhere. It seems like if very high FC levels were capable of "burning CYA" to lower the CYA level, that would be a very commonly-prescribed approach on this form. Why drain/fill and then slam when you can just slam at "burn off CYA" level and kill two birds with one stone? That makes me question whether this "CYA burning" is real.
Click to expand...

It is possible to increase the oxidation reaction of CYA but the FC levels would have to be quite high (shock level FC) and the reaction is quite slow. So, in practical terms, chlorine oxidation of CYA at normal FC levels can be measured but effectively ignored. You're likely to lose more CYA through splash out or back washing.

ChemGeek could point you to one of his many posts on this subject if you're interested but I would start another thread for that.

Here's ChemGeeks post -

http://www.troublefreepool.com/showpost.php?p=69523


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Re: Unexplained FC Consumption (updated title)

I sure don't have the answer to what is going on in your pool but I have been following this thread due to my past issue with loss of FC at a substantial rate.

My FC loss is due to my travel schedule also but also to my inability to scrub the pebbletec surface as much an needed.

I would like to add that my CYA was at 60 and I had been adding a jug or two of 8.25% while away for 3 days each week to keep the algae at bay. I have been adding a ridiculous amount of MA lately to try and push down my pH below 7.8 and it keeps climbing back up. I had adjusted my TA to 120 and thought that was the reason for the acid demand. (I used to use trichlor for shock and pucks to keep it from being a swamp but never had a sparkling clean pool until this year. I never added acid but constantly fought the TA along with the algae.)

After reading your thread (along with ChemGeeks posts) now I can see that my pH and TA was low from my past trichlor use. Now with 8.25% I have to use acid while the TA drops and the pH levels off some. My constant use of hyper bleach dosing is causing me to lose CYA at an accelerated rate. Time to recheck that for sure. Time for me to splurge on a SWCG in the near future.

Regarding your situation- With my limited knowledge, it seems that the FC drops faster during direct sunlight the higher above target FC you go. Your use of a cover should have substantially reduced that drop though. The higher the pH, the less effective the FC is at killing the algae so maybe keeping it closer to 7.2-7.4 might help. Removing the cover will be telling regarding it's contribution to contamination. I would at least try the mustard shock level of FC to rule out that as a source and to put a dent in the mutated algae you have created :). My main suggestion is that you enjoy your beautiful pool and keep in mind that bleach is cheap and a little scrubbing is good exercise:)
 
Re: Unexplained FC Consumption (updated title)

Daltex,

The higher the pH, the less effective the FC is at killing the algae so maybe keeping it closer to 7.2-7.4 might help.
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The affect of pH on the sanitizing power of chlorine in pool water with CYA is actually not strongly related to pH. I made the same mistake thinking that and ChemGeek has an excellent post detailing it here -

http://www.troublefreepool.com/showpost.php?p=4121

In short, once you add even a small amount of CYA, it completely shifts up and flattens the standard HOCl/OCl- versus pH S-curve. Only at ridiculously high pH values (>8.2) do you see any significant shift in the FC towards hypochlorite. At TFP suggested ranges, >90% of the FC is HOCl or Cl bound CYA.


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Re: Unexplained FC Consumption (updated title)

SunnyOptimism said:
Some more questions -

You always quote dosing in ppm of FC, but I assume your Stenner is set based in volume flow rate. What's your volume flow rate on the Stenner? How much can it deliver and over what time period do you deliver chlorine (slow drip, fast burst, etc)?

Any chance your wife would be willing to learn how to use your chemistry set and get some reliable numbers while you're away? Perhaps you can bribe her with a promise of taking her on your next business trip or buying her some nice jewelry.

Keep us posted on the results.


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Click to expand...

Stenner is a fixed rate - mine is 10 gallons per day, so it 'flows" in around 50 oz per hour.


I tried to get her to learn to test, but she just claims it is too complicated and refuses to learn...I've tried a few times but no go. I keep trying though.

- - - Updated - - -

SunnyOptimism said:
Daltex,



The affect of pH on the sanitizing power of chlorine in pool water with CYA is actually not strongly related to pH. I made the same mistake thinking that and ChemGeek has an excellent post detailing it here -

http://www.troublefreepool.com/showpost.php?p=4121

In short, once you add even a small amount of CYA, it completely shifts up and flattens the standard HOCl/OCl- versus pH S-curve. Only at ridiculously high pH values (>8.2) do you see any significant shift in the FC towards hypochlorite. At TFP suggested ranges, >90% of the FC is HOCl or Cl bound CYA.


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Click to expand...

In reading chemgeeks quote again, he mentions a few times "this does not account for CYA loss during the summer when FC is present and bacteria should not be growing, etc..." or something like that.

So what I surmise from that is it is possible under certain conditions to loss CYA - which is PART of my problem.

I honestly think that quite a few of us this year have some problem that we have never really been able to figure out, and then it goes away or it is not that common. Could it be the cold winter ? I wish somehow we can all try to work together and figure out the common thread....it has to exist.
 
Unexplained FC Consumption (updated title)

I tried to get her to learn to test, but she just claims it is too complicated and refuses to learn...I've tried a few times but no go. I keep trying though.
Click to expand...

The rocks, bro, the rocks....dangle a nice little tennis bracelet full of the shiny clear carbon and I bet you'd get a little more attention to detail....but that's a post for The Coffee Bar forum :p


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Re: Unexplained FC Consumption (updated title)

toofast said:
.........So what I surmise from that is it is possible under certain conditions to loss CYA - which is PART of my problem.

I honestly think that quite a few of us this year have some problem that we have never really been able to figure out, and then it goes away or it is not that common. Could it be the cold winter ? I wish somehow we can all try to work together and figure out the common thread....it has to exist.
Click to expand...

ChemGeek did suggest that the CYA is lost from chlorine. per ChemGeek-"So, assuming a CYA loss rate of around 0.4 ppm/day in our pools this comes to 12 ppm per month which is clearly enough to be noticeable as the months pass during a swim season. If one shocks the pool, then the rate of loss could be about 2-3 times faster." The higher the FC the faster the CYA loss. It's just not at a pace that would justify using bleach just to lower the CYA.

Sunny was showing me the relationship to lower pH to effectiveness of the FC which I did now read and kind of understand now that the pH doesn't have much effect on FC at normal levels.
 

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Re: Could bad DPD or R-0871 cause wacky results

toofast said:
As for Ammonia - yeah that is kind of what I thought...during this WHOLE MESS I never had CC above .5

Yes, pump was running on low when injecting, then on high for 30 min after to get accurate mix. Was also running overnight on low when passed test overnight.

Test kit is stored inside in covered uv resistant box in dark under a cupboard. in winter stored in dark cool basement. Both DPD and 871 are on second season.

I will do the test and see what we come up with...still BAFFELED how I lost 5 PPM in 5 hours -but that is a different story I guess. Stay tuned...the test will have to be later this evening though.
Click to expand...

Ok- I have a new theory. I'll need the experts to confirm of course. You have excess loss of FC but low to zero CC. Soooo.... what about the possibility that the CC's are being oxidized by the FC while under the cover because the cover keeps the water from off gassing the by products of the oxidation of the CC thus not being able to eliminate them. The CC's are in essence replenishing themselves due to the cover trapping the off gassing but the FC is able to oxidize them.

I know ChemGeek would know if this is possible but I of course do not know. Just a thought I had.
 
Re: Could bad DPD or R-0871 cause wacky results

No, it would be more likely the opposite. If the pool was covered then if there are CCs formed that are slow-to-oxidize and would otherwise be volatile if no cover is present then a higher CC would be expected with a cover. Without a cover, any volatile CCs will have more chance to outgas. Also, sunlight helps break down some CCs directly (e.g. dichloramine) and others indirectly via hydroxyl radicals produced from UV breakdown of chlorine. This is why outdoor residential pools exposed to sunlight usually have very little CC. Indoor pools even with low bather load have more of a problem controlling CC.

Regardless of whether a cover is present, chlorine continues to oxidize CC, but how quickly this occurs depends on the specific chemicals involved. Chlorine combines with ammonia to form monochloramine VERY quickly, in less than a minute even with CYA in the water. It takes hours for the chlorine to oxidize the monochloramine and this as well as formed dichloramine will measure as CC (some nitrogen trichloride is produced as well, but not enough to show up as CC in residential pools). With urea, it takes a long time for chlorine to react with it to form chlorourea but then it's much faster (in hours) to get further oxidized. In many pools, the CC that persists the most is likely to be chlorourea but fortunately it is not volatile nor irritating.
 
Re: Could bad DPD or R-0871 cause wacky results

Daltex said:
Ok- I have a new theory. I'll need the experts to confirm of course. You have excess loss of FC but low to zero CC. Soooo.... what about the possibility that the CC's are being oxidized by the FC while under the cover because the cover keeps the water from off gassing the by products of the oxidation of the CC thus not being able to eliminate them. The CC's are in essence replenishing themselves due to the cover trapping the off gassing but the FC is able to oxidize them.

I know ChemGeek would know if this is possible but I of course do not know. Just a thought I had.
Click to expand...

Dang - I am kind of bummed that chem geek cleared this up for us, at least it would give us a theory that sense :(
 
Re: Unexplained FC Consumption (updated title)

No update, other than it has been SUPER HOT (high 80's) the past 3 days and my wife forgot and covered the pool :) (she just told me tonight when I asked, so I guess I will leave it on till tomorrow when I get home)

Due to the heat, she had a few neighbors over each evening and swam for 3-4 hours...and she claims the pool is crystal clear still.

So much for the cover experiment.

I will test and post results tomorrow at some point.
 
Re: Unexplained FC Consumption (updated title)

toofast said:
No update, other than it has been SUPER HOT (high 80's) the past 3 days .....
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Hahahahahahahahahahaha ..... ROFL!

Try 104+ for three days straight down in these parts....

Bummer about the pool cover experiment. However, if she's truly sorry for messing up your wet chemistry lab, perhaps you can shame her into learning how to use the Taylor test kit :eek:



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Re: Unexplained FC Consumption (updated title)

Well, I'm from NY originally so I know humidity. It's "monsoon" season here in Tucson and all the locals complain about it being humid but I'm like, "humidity? Seriously? " so yeah, it's all relative.

I left NY to get away from the cold and humidity!

When you get back, roll the cover off and put a lock on the reel. Let that pool breathe some fresh air for a bit.


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Re: Unexplained FC Consumption (updated title)

I know I am going to be bummed soon....

Meaning when I left all of a sudden it looked like my FC was starting to hold...and NOTHING CHANGED.

So after nearly 100 gallons of bleach, I will have a clean pool with really no explanation. UG !
 

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