Water is beautifully clear. FC is 0...

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S

Sandrat

0
Jun 27, 2016
23
Osawatomie, KS
Dear Pool Geeks,

26,000 gal
SWG
FC 0
CC .5
Ph 7.5 (just added acid to get to 7.2)
CH 200
TA 80
CYA 80
Phosphates 0


Here's my issue:
The water is clear and beautiful, yet the FC is 0. My oversize RJ45 CircuPool SWG is running 24/7 at 100%. I can see gas clouds through the ionizer, so I know it is working. I added a lot of shock early in the season that wouldn't stick , but found my CYA was a very low 10. I have added dry acid this year to raise the CYA to an almost-too-high 80. Now, after raising the CYA, I'm still adding shock, but with no rise in FC. I think I have a subtle algae bloom, but it could be chlorine lock, or a combination. After reading countless forums, I think the answer is to get to Breakpoint Chlorination, but I feel that the information out there is a little inconsistent.

Using the Chlorine/CYA chart from this forum, I see that a shock value of 31 is recommended. Yet this is higher than the pool calculator's suggested shock level, which recommends a 21. Also, when I read about Breakpoint Chlorination, it seems to be a one time process, yet the SLAM program looks more like an ongoing process over several days.

So, is SLAMming the pool is different than the Breakpoint process? Since I have no visible algae, should I use different shock levels? I just want to do this right, hopefully for the last time this season. If it takes a few days, I need to be sure I have enough chemical on hand so that it doesn't get away from me if I run out.

Thanks for the help, and please don't flame me for asking a question that may have already been answered. There are a lot of threads to sift through, and I feel like the clock on the algae bomb is ticking...
 
Hello and welcome to TFP! :wave: I see one very major issue ahead of you besides no FC level recorded .... pool store testing. The sooner you break-away from the free store testing and test your own water the better you'll be. I would recommend the TF-100 (link below) although the Taylor K-2006C will also work. But you must test your own water.

Your CYA may be much higher than what the pool store indicates. But for FC, it's either eliminated by the sun or organics/algae, To truly know which one it is you must have one of those recommended test kits. Please try to get one of those and post a full set of results for us when it arrives. That will give us accurate info to go on. In the meantime, please visit all the vital links you see below in my signature, and make sure to update your signature as well please.

Nice to have you with us.
 
I use a Taylor K2005. It is a DPD only, not FAS.

My CYA measurement was actually higher, between 90 and 100, but I found it difficult to read accurately. I always do my own testing, but to rule out test chemicals that may have weakened with age, I took the water up to pool store to confirm, especially the CYA.
 
Oh good. Then with the 2005 kit, all you need is THIS PART to make it a 2006 version.

CYA testing can be tricky, and if it's as high as you suspect it might be trickier. Have you tried a diluted test just to see?
CYA Dilution Testing:
Add pool water to bottom of sticker. (or 7ml line)
Add tap water to top of sticker.
Shake.
Pour out half so mixture is to bottom of sticker.
Add reagent to top of sticker. (or 14 ml line)
Shake.
Test outside with back to sun and tube at waist level.
Pour back and forth a few times to see if you get the same result.
Double the result.
Click to expand...

- - - Updated - - -

I'd like to give you some recommendations on increasing FC and testing or performing for a SLAM, but that's not possible until you are able to get the FAS-DPD portion to test FC at the higher levels required based on on your CYA.
 
OK, will do the diluted test tonight after work, I would like to have a more accurate CYA reading. I will post the results.

Maybe you can answer my general question about the difference between SLAMming the pool, and Breakpoint Chlorination. SLAM looks to be a long, multi-day, process, while BC looks to be a one shot deal (assuming you reach the required shock level). Or am I missing something?
 
"I have added dry acid this year to raise the CYA to an almost-too-high 80. Now, after raising the CYA, I'm still adding shock, but with no rise in FC."

I may have missed it, but dry acid shouldn't affect your CYA. Adding shock, if powder, will raise your CYA but I don't think dry acid will move CYA.
 
"I have added dry acid this year to raise the CYA to an almost-too-high 80. Now, after raising the CYA, I'm still adding shock, but with no rise in FC."

I may have missed it, but dry acid shouldn't affect your CYA. Adding shock, if powder, will raise your CYA but I don't think dry acid will move CYA.
Click to expand...
I saw that and just assumed the OP meant dry (cyanuric) acid. Come on Sandrat, don't make a liar out of me. :)
 
Something else brought to my attention (thanks pabeader aka - Bob), you mentioned above you're using the DPD for FC testing. I found this reminder in another thread:
DPD is a little more problematic as a daily test, as it can read zero when FC is above something like 12, which can be very misleading.
Click to expand...
It's very possible that your FC is high simply to off-set and stay with the high CYA. That could explain why your water is still clear. Just another reason why the FAS-DPD test kit portion is so valuable to what we do here on a daily basis. Hopefully you get that powder/drop portion soon so we can nail-down some of these "unknowns".
 

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Update: I did a diluted CYA test and found the "half" reading to be between 45 and 50, so total actual would be 90+

I won't have the FAS test kit for a couple of days. I noticed this morning that the water is looking a little "milky". No color tint, but not as crystal clear as it was a day ago. I have been running my Polaris continually to keep the bottom and side walls swept off.
 
Sandrat said:
I have been running my Polaris continually to keep the bottom and side walls swept off.
Click to expand...

I think you will be better off brushing and vacuuming to waste. The Polaris bag is great for leaves and larger particles. But I believe it's too porous to get rid of any organics and it doesn't do what manual brushing will do.

In meantime, keep that FC up there to avoid that algae time bomb you speak of.
 
Here's the thing: I haven't added any shock yet, as I'm waiting on some advice. But I was told that I needed an FAS test and to report the results back....a kit I need to order and wait on....

My original question was do I need to shock to the Pool Calculator level of 21? Or to the Chlorine/CYA chart of 31 (based on what I thought was an 80 CYA)? Or is my CYA level creating a chlorine lock? (maybe now even more relevant, since the number appears to be in the 90s).

I don't want to waste a $60 box of 73% CalHypo shock if I can't get the FC level up high enough due to CYA levels.
 
Here's what I would do. That 90 CYA is a bit unmanageable, even for a SWG pool.

1. Start brushing the sides - really brush to get up that "milkiness" you are describing. Then vacuum to waste. You don't have to dump a lot. If you can dump about 10-15% and refill, that will get your CYA to about 75-80, which is nice for a SWG. It will also take down your Calcium from 200 to about 170-180.

2. Refill and start start getting some liquid bleach in there. (If in doubt how much, overshoot it)

3. Once refilled, lets get some fresh test levels. If your CYA is now in a better zone, it will be more manageable.

4. No one like to "waste" what they bought. CH is not a huge factor with your vinyl pool. But now that it will be lowered a bit, go ahead and use that Cal-Hypo you have. I will do some calculations in a bit, to see how much you can actually use w/o going too high, but I doubt you will. Once you are done with what you have, don't buy it anymore.

Be back with more info in a bit. gimmie a few.
 
When I plug your numbers into the pool calculator, it shows your shock level as 31. I would not use cal-hypo. For your pool each 16 ounce bag of 73% cal-hypo will raise FC by 3.3 and raise calcium by 2.4 It would take 9lbs of cal-hypo to reach shock level one time. We recommend liquid chlorine instead of granulated shock products. If you complete the slam process you will need to raise the pool to shock level and keep it at shock level until the process is complete. That involves checking FC levels and dosing the pool every couple of hours. Using cal-hypo for this will be very expensive. The slam process does take a few days to complete. How long it takes depends on how much organic debris is in the water. Pools that are already mostly clear tend to complete the process more quickly.
 
zea3 said:
I would not use cal-hypo. For your pool each 16 ounce bag of 73% cal-hypo will raise FC by 3.3 and raise calcium by 2.4 It would take 9lbs of cal-hypo to reach shock level one time. We recommend liquid chlorine instead of granulated shock products................Using cal-hypo for this will be very expensive.
Click to expand...

But she has it already.....

Sandrat said:
I don't want to waste a $60 box of 73% CalHypo shock if I can't get the FC level up high enough due to CYA levels.
Click to expand...

She can certainly use what she has as some kind of a source of chlorine rather than toss in the garbage. Using my partial drain method, it won't get he CH levels off the charts.
 

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