Success !

[Sprocket]

FC 10
CC 0
TC 10
PH 7.4
CYA 42

After a week of shocking this pool to over 24 FC at one point I had given up on ever getting the CC to 0 .

So I went and took out 15in's of water friday night as my CYA was 65 at that time . After 25 hours of slowly refilling the water was slightly green with a FC lvl of 11.5 . I added 2 3quart jugs of 6% bleach , that was Sunday night .

Monday I got in pool with FC lvl 11.5 and brushed really good again . Today Tue I have the above numbers yaaaa .

Pic included from today , also one of how I weight down my stairs , really easy now to pop those out and in as the weights are just used clorine jugs filled with sand and topped off with pool water . I tied the handles together with rope and just hang them over the stairs .

Anyway after almost giving up I thought that at least with the CYA below 50 I could at least get the clorine lvl down so that it wouldn't dry out my finger tips so bad as I am in chemicals at work also and cracking is a problem .

I "guess" that with a lower CYA that the clorine was able to work better . Donno but I am sure happy today about my pool .

Thanks all
Sprocket

[chem geek]

First of all, congratulations on beating your algae! Your results are interesting.

This may be some evidence that the shock levels in Ben's Best Guess CYA Chart may be too low at the higher CYA levels. My calculations of disinfecting chlorine (HOCl) levels at various levels of CYA show that Ben's table roughly correlates to around 0.03-0.07 ppm of HOCl for the Min./Max. ranges, but the shock ranges do not correlate.

Your data would imply that 24 FC with 65 CYA is not sufficient, but that some unknown level above 11.5 FC worked with 42 CYA. This chart shows the FC level required to achieve the specified level of HOCl and you can see that at a shock level of HOCl of 0.5 ppm, you would need about 30-35 ppm FC at 65 CYA while you would only need about 20 ppm FC at 42 CYA. A decent rule of thumb would be that for shocking, you need to bring your FC to half your CYA ppm level.

Your lack of success at 24 FC and 65 CYA also shows that the HOCl level required for killing algae is probably above 0.3

Of course, you might have actually been killing your algae over that week, but too slowly for you to notice (and I mean "killing" in a net sense that you kill faster than it reproduces). At any rate, thank you so much for keeping track of your numbers as we are trying to quantify exactly how much FC is truly needed at each CYA level and I'm putting my money on 0.5 HOCl for a "quick" kill and perhaps 0.3 HOCl for a slower kill.

Richard

[Simmons99]

Holy cow - If I understand your post you are stating if you had a CYA of 100 - you would need to shock to 50ppm (poor vinyl liners )?

Personally - I would try the Best Guess Chart first and then raise 5ppm a day until I saw some progress if needed.

[RavenNS]

Congrats on beating the Algae.
Your water looks beautiful !
wtg & great job; give yourself a big pat on the back

[chem geek]

Holy cow - If I understand your post you are stating if you had a CYA of 100 - you would need to shock to 50ppm (poor vinyl liners )?

Personally - I would try the Best Guess Chart first and then raise 5ppm a day until I saw some progress if needed.

Your pragmatic and safely incremental approach is certainly the way to go. We're not officially changing Ben's chart just yet (only Ben can do that and only after real-world experience bears this out), but it may very well be true that to get rid of algae quickly, a shock to 50 ppm FC is needed when the CYA is 100. HOWEVER, keep in mind that 50 ppm FC isn't really as high as it sounds when there is CYA of 100. IF what damages vinyl liners is the oxidizing and disinfecting form of chlorine (HOCl), then this level is only 0.5 ppm which means that as far as the vinyl liner is concerned, it is being exposed to exactly the same amount of chlorine as if it was 1.0 FC with no CYA (assuming half is HOCl at pH 7.5).

Again, this is speculative "theory" at this point, but the more evidence I see, the more I'm thinking it's true.

Richard

[Sprocket]

Numbers Sunday night after the refilling pool just so there is no misunderstanding .

Friday just before taking 15in of water out 24FC - CYA 65

Sunday after water put back in 11.5 FC - CYA 42 added another 6 quarts of bleach , now pool was about FC 17.5 total or so , did not recheck after adding 6 quarts .

Monday night FC 11.5


Tue night FC 10

Wed night FC 7

Interesting note for me at least , tonight I checked for CC again tonight (Wed) and it was .05 again grrrr , but I was thinking back and I didn't shake the tube very long like I had on Tue. So after thinking on this I wondered if I had gotten all the powder really mixed with the pool water . So out I went to get another pool water sample and this time I really shook that tube a long time to get the little bits on the bottom really almost gone , don't know if the last 3 or 4 ever go away ? Anyway this time it was clear like on Tue night after the 5 drops .

NOW I wonder if I was doing the CC test correct or not all these weeks ? Had I been not mixing the powder up enough ? Donno sigh . Can that happen if you don't mix the powder regent long enough ? I would hate to think that I was that dumb and had used that much bleach for so long just because I had not mixed it well enough

Anyway it's looking great and this forum has really saved my marriage and the pool hehe at least the pool , don't know what would have happened if I had took that axe to the sides .

SO <S> to u all
spro

[chem geek]

Friday just before taking 15in of water out 24FC - CYA 65

Sunday after water put back in 11.5 FC - CYA 42 added another 6 quarts of bleach , now pool was about FC 17.5 total or so , did not recheck after adding 6 quarts .

Just for completeness, the 24FC - 65CYA combination has 0.265 ppm disinfecting chlorine (HOCl) while the 17.5FC - 42CYA combination has 0.324 ppm which is not a huge difference. So either the "cutoff" for when a much faster algae kill occurs is somewhere closer to the 0.3 ppm range (rather than 0.5 ppm as I had thought earlier) or you were just hitting the alage hard for a week and it just coincidentally overcame the algae around the same time you decreased your CYA.

The "rule-of-thumb" for hitting a 0.3 ppm disinfecting chlorine (HOCl) level for shocking would be an FC that is about 40% of the CYA level. Still high, but not quite the 50% needed to hit the 0.5 ppm level.

Richard

[Sprocket]

Just thought I would check in again .

All's well this year , we took the cover off on Thus just before Memoral Day and no algae on the bottom or sides but the water had a slight green tint to it .

I added 6 jugs of 6% Ultra bleach and the next morning it was crystal clear and tested 17.5 FC . Vac and sweept the pool that morning and we got in Friday night water was 71 degs and it was HOT out already , felt so good .

Now it's been two weeks and NO PROBLEMS at all . I really feel that lowering the CYA did the trick for my headaches , plus following all your good advice . I seems like the first year I had the pool ( 2 years ago ) .

NO CC this year , yaaaaaaaaaaa . Been runing my FC at 4 to 7 , just add a 3 quart jug when the FC drops below 5 .

I just wanted to give a BIG THANKS <S> to all that run this bb board and for the help etc .

I been trying to stear some people from work here but you know how that goes ? When they find out that they need a good test kit , they start to haze over

Thanks again
sprocket