One annoying little number...

[ecowolf]

Okay; so as I mentioned, in another post, the pool is looking great, water is clear, all numbers look good:
FC 6
PH 7.6
CC 0
CYA 50
TA 105
CH 320

However, after a couple of Overnight chlorine loss tests, I am getting a 1.5 drop in chlorine overnight. I realize that the number to be concerned about is "greater than 1." So does 1.5 qualify? Now, granted, I didn't actually get to my morning tests until about 30 minutes after sunrise each time, but even then, the sun was still behind a big mountain. Should I be concerned about this number at all? Do I need to shock, just to be safe, or since the pool looks fine just forget about it and stop being so OCD?

 

[Leebo]

I'd bring your FC level up to the top end for your cya level (FC of 8) and try another OCLT tonight. A drop overnight shows something is trying to grow....kill it before it gets worse.

 

[Christian]

A 1.5 loss overnight is a sign of bad things coming down the pipes. Bring your FC up until you lose less than 1 ppm overnight.

 

[ecowolf]

So, should I bring it up to shock level (20ppm), or just up to the high end of my CYA range (8ppm)? Quite a big difference...

 

[jblizzle]

I would say shock level.
If you pass, the FC will drop below shock level in a few hours of sun and be safe to swim.
If you fail, you have already started the shock process.

 

[ecowolf]

Okay. Shock it is. Will start tonight. Darn, and I thought I was done!

 

[fast1971chevelle]

better to be safe than sorry but i think you caught it early enough.....good luck....Mike

 

[ecowolf]

Well now I'm really stumped. Last night I poured in over 3 gallons of chlorine to bring up the FC to 23.5. This morning it was at 19! Why did I go from a consistent OCL of 1.5 to suddenly a loss of 4.5??? Is it normal to lose more chlorine when shocking? I really hope I'm not screwing something up. And man, is this eating through the testing reagents!

 

[linen]

What was your CC value?

Did you measure the 23.5, or just assume?

When you have 1.5 drop with "normal" FC levels, you may have been just barely loosing ground with the algae. Now that you have raised it up the chlorine is winning and killing algae at a higher rate.

Did you do a lot of brushing yesterday (by the way you should be brushing if suspect algae)? If you did, that may have rubbed open biofilms protecting some algae that then were being killed and using the chlorine at a higher rate then before.

 

[ecowolf]

CC is 0, and has been. Yes, I tested all numbers, twice, sometimes three times. I wasn't brushing because there has been no sign of algae. I've tried to brush, and there is absolutely nothing to brush. The sides are clean as a bell. The water has been crystal clear. The only reason I did this is because of the 1.5 loss overnight.

 

[linen]

Well it is good you raised your FC level up, since it appears that you have organics that need to be removed. Proceed with the shocking process.

 

[ecowolf]

Yeah, thanks. Still going with it. It just was not what I expected at all.

 

[ecowolf]

And I hope that I don't have to do this shock process again for a long time. It is quite time consuming, and not cheap. =/

 

[ecowolf]

So last night I bumped the FC up to 26that to try and keep from getting below 20. This morning it was at 20. So my overnight loss was 6. Should I bump things up to yellow mustard level at this point? I know its only been 36 hours, but should it take this long when my water was crystal clear to begin with?

 

[PAGirl]

And I hope that I don't have to do this shock process again for a long time. It is quite time consuming, and not cheap. =/

Probably still much cheaper than going to the pool store! Good luck, I hope it levels out for you soon!

 

[jblizzle]

Just maintain 20ppm until you pass the 3 tests.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[ecowolf]

Okay. Will continue shocking. I do appreciate all the help. As with the other processes in converting to BBB, this shock process seems very "unorthodox" for lack of a better word, what with going through gallons and gallons of bleach and bottles and bottles of reagents. So confirmation that what I am experiencing is "normal" is good to hear.

One suggestion I might offer, based upon the viewpoint of someone doing the BBB shock process for the first time. This may just be my perception, but I think if a couple more sentences were added to "The Shock Process" article in Pool School, it might help some people know better what to expect. Perhaps a sentence or two covering:
1. The fact that when you are shocking you may start losing FC at a much more rapid rate than you were before.
2. You need to bump the FC up 2-5 ppm above shock level before you go to bed to avoid dropping below shock level overnight (this was mentioned in several posts, but not in the Pool School Article).
3. This point may just be my experience, but if my experience is typical, maybe something about that if you are shocking at relatively high levels (20 in my case), you could expect to be losing FC at a very rapid pace and therefore testing during the day will need to be done very frequently, sometimes as much as every hour to make sure you don't drop below shock level.

Just some ideas that might help other newcomers to this process.

 

[ecowolf]

Things may be looking up! Whereas yesterday I was losing 4-5 ppm per hour and FC was swinging around almost unpredictably, today after 3.5 hours of direct sunlight, I've lost no FC! In fact, it has gone UP slightly since this morning, which I find very strange, but hey, I'll take it! Will keep shocking and cross my fingers for tonight's OCLT!

 

[UnderWaterVanya]

Things may be looking up! Whereas yesterday I was losing 4-5 ppm per hour and FC was swinging around almost unpredictably, today after 3.5 hours of direct sunlight, I've lost no FC! In fact, it has gone UP slightly since this morning, which I find very strange, but hey, I'll take it! Will keep shocking and cross my fingers for tonight's OCLT!

It can't go up. That could mean that:

You may not be waiting long enough after adding the bleach to get an accurate starting number.

It's also possible that at times you are going too slowly between drops and the readings are giving falsely high FC levels.

Have you viewed the youtube video's of the test?

 

[ecowolf]

I think this is probably a case of not waiting long enough after adding bleach. I did wait about 45 minutes, but perhaps that wasn't long enough. Yes, I've watched the video. I am very careful about counting the drops and the timing. I tested it twice, as well.

And now it has dropped by 3, which is about what I would expect with full sunlight.