SLAM - odd numbers

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simonoaks

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May 28, 2015
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Juno Beach , Florida
HI,

Think the recent hurricane in FL flooded my pool and diluted CYA; I noticed a drop in FC over a few days, even though I increased SWG up to 85%, tested CYA and it was zero ( well clear to the top of the test), so I added CYA and raised it to 60 (then stopped as I realized I may have to do a SLAM and have done it at 90ppm before and it is a grind). 3 days ago it was at 7ppm, then this morning, when I got back from a business trip, it was at 1.5. Clearly an algae issue.

I went to the store and bought 8 bottles of Clorox (126 oz per bottle). timeline is thus:

11am - fc 1.5
1pm - added 4 bottles
2pm - fc 17, added 2 more bottles
3pm - fc 20, added 2 more bottles

According to poolmath, my 10,000 gallon pool needs 450oz to raise it to the target 24pm for 60 CYA. I have had to add DOUBLE that.
I did turn off SWG for this, bet kept the pump running.

Is it normal to have algae eat up such large quantity of FC in first 2 hours ? I have not seen that in the numerous SLAMs I have done over the years. Particularly as there is no noticeable discolouration of pool or water.

Any other reason why I had to add SO much bleach to raise my FC from 1.5 to 24 ?

I will take another reading at 4pm to see what impact the last 2 bottles had.

thx
 
5pm , FC 18.....crazy. Will do the overnight test to see what is going on. Not seen anything like this before - over 1,000 OZ of bleach into a 10,000 gallon pool and not reaching shock level......I could understand it if it was like a couple of years ago when I could physically SEE the algae dust as I swept and the green coming out when cleaning filter....but this time, no visible signs at all. Very odd.
 
Sat 6.15 am
Fc 11.5
So, lost 5ppm overnight. Not bad considering how much FC it consumed yesterday, guessing around 30ppm.

- - - Updated - - -

Also, I have a load of foam on pool surface, generated by small waterfall , since adding the bleach, any idea what that is ? Thx
 
I have not measured CC ... on every test - just the first one, and it was zero - good point.
Water did not seem cloudy.
I do actually have a bacteria test kit (the whole reason I took over my whole pool was because my little girl had lots of surgery on her leg and open wounds for 6 months, so I wanted to make sure pool was clean and bacteria free)

Will check CC on next test; just did one:
11.30 am - FC 10
So down 1.5 - but that is SWG on 60% as I turned it back on at 6am.... so FC still being eaten.
Added 4 more gallons of Bleach - Publix own brand , unscented, easypour (only one they have).

Will check CC when I do next reading in 1hr to make sure I am back up to SLAM fc 24

I did not know bacteria ate CYA, interesting.

Will the SLAM kill the bacteria, like it does with Algae ?

thx
 
Don't use easypour bleach. Only regular that says 8.25% sodium hypochlorite on the label.

Bacteria is easily killed by a SLAM.

No need to drain. Just finish out SLAM.

If the percentage is not on the label, it's probably much weaker and would explain why the amount added did not give the expected fc.
 
Ok. Thx. Added 3 more gallons. That's 12 gallons for 10k pool ! Must be weak, as pool math says it should be fc 60 !! Think I am getting 2.8 ppm per gallon, instead of 4.5. Will go to walmart next time !!

Will the scent chemicals stay in my pool and ruin it ?
 

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The scent and soap from those types of bleach will dissipate over time. It just consumes more bleach.

Get plain bleach.

Take care.
 
8pm - fc 18, added 2 gallons of regular bleach 8.25%
9pm - fc 31 - now we are cooking !! That will likely do it, based on my past experience. So I should be be able to let it naturally drop with SWG off over next couple of weeks?

I forgot, do you know the safe-to-swim FC to CYA ratio, after slam. last time I recall it being something like it was ok to swim with fc 15 and below for CYA of 80. thx
 
I recommend you follow the SLAM Process protocol. Just getting your FC to some level and then letting it drift down is not a SLAM. Review the SLAM Process article to be able to pass the three criteria for a successful SLAM.

Also, your pool is safe to swim in if your FC is above minimum and at or below shock level based on your CYA, see [FC/CYA][/FC/CYA], your pH is between 7.2 and 7.8, and you can see the bottom of the deep end of the pool.

Take care.
 
Ok . Thx. Yes, you are right - I have taken short cuts before with only a 50/50 success rate.

My problem has always been that it is just not possible to accurately measure and FC drop of less that 1 , at shock levels, several reading one after the other are always out by +/- 1.5-2

Here is latest:
8 am - fc 17, added 2 gallons
10 am - FC 23
2 pm - FC 12 , added 2 gallons
2.50 pm - FC 31
CC less than .5 on all tests

Question: would the chemicals/ soap , whatever ingredients that were in the scented bleach I added, eat the FC just like algae would? Pool is crystal clear, so wondering if that could cause the same FC loss as algae . Thx
 
The bleach additives will not consume your FC like that. And you report a fairly high CYA so the fall sun should have little effect too.

When you do a OCLT is the one time you are best to use the 25ml sample when testing the FC. It gives you more accuracy and less chance of seeing the range you state.

A clear pool is one of the three criteria. Once your FC holds better during the day, then you should do a OCLT.

Be sure to check any ladders, light niches, skimmer doors, etc for hiding algae.

Take care.
 
Did not get to do morning test.
12.45 pm - FC 15
Had sun on it since 7am , so not too bad.
Also, tested CYA and it is at 40 (well between 60 and 40 , as we all know, it is a totally inaccurate test.) 60 in sunlight, 40 in shade (prefer shade as it is impossible to see in sunlight because of the concentrated reflection in the middle of the tube. Not sure why we cannot have an accurate test method, as with all the other tests - on drop-by-drop basis.

Anyway would you say an FC loss of 5 from 7.30pm to 12.45 pm , with CYA of 40 was normal loss, or should I go buy more bleach and raise it back up again ?

thx
 

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