Couple of Chem questions

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AzWildcat

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Jun 22, 2007
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Texas
Just finished a week and a half war with the dreaded black algae and am claiming victory. Just got a TF-100 kit yesterday and am now in the process of bring our pool into balance and beginning the BBB method. We have a 25,000 gal plaster pool with a DE filter. I will be taking the filter out this afternoon, degreasing it, and recharging it with DE.

My goal is to achieve a CYA level of 40 and keep the FC at about 6.6 to meet the CL/CYA Yel/Mustard algae min. and provide a .5ppm buffer. Presently I am at 20ppm CYA and 10.5ppm FC. My pH is reading 8. I had been running at very high CL levels - 40-50 ppm. It is hot here and I have a fountain so can take the FC down fairly quickly.

I have read that pH, TA, and Ch readings are inaccurate at high CL levels.

1) At what point (in FC test readings) can I "trust" my pH readings and make an informed trip to the Pool Calculator and adjust my pH ? At what point can I "trust" my TA readings ?

2) After I Pool Calculator calc the CYA needed and add the stabilizer, approx. how long does it take with a clean DE filter that won't need backwashing for awhile to test accuratley for CYA ? Should I add the stabilizer all at once or over time ?

3) Should I wait until after adjusting pH and FC and adding CYA to adjust for TA, if necc ?

4) I thought I read somewhere that with the TF-100 it was possible to test FC in .2ppm increments (instead of the .5ppm that the kit articulates) by altering the test procedure somehow. Am I crazy ?

It has been a long two weeks. I want to thank everyone in this forum for their help. I have learned a lot and am very grateful for the amount of knowledge, however small, I have picked up from this forum. While I have never been to prision, I do think I know how someone feels when they are about to be released.
 
1) If FC is 10 or lower the PH reading should be usable. With FC between 10 and 18 the PH will read a bit higher than actual but more or less alright.

The TA and CH tests are valid up to very high FC levels, though the colors may be a little different at high FC levels than they are at low FC levels.

2) CYA can take up to a week to dissolve. I would give it the full week, just to be sure, even though it will likely take less time than that to dissolve.

3) You can start on lowering TA as soon as FC is going to stay at 10 or lower. It doesn't really interact with the other numbers much.

4) Yes, the FAS-DPD test can be done by 0.2, but the directions are not included with the test kit. You can see the alternate directions here.
 
Thanks for the help and the link.

Want to verify an assumption that I think is correct. Does the Yel/Mstrd Min in the Chlorine/CYA Chart mean the min level of FC above which, given a measured level of CYA, that Yellow or Mustard (and by extension Black) Algae will NOT grow in a pool ? Or, does it mean those are min levels that those algaes will be KILLED should they enter the pool ?

Again, thanks
 
AzWildcat said:
Does the Yel/Mstrd Min in the Chlorine/CYA Chart mean the min level of FC above which, given a measured level of CYA, that Yellow or Mustard (and by extension Black) Algae will NOT grow in a pool ? Or, does it mean those are min levels that those algaes will be KILLED should they enter the pool ?
Click to expand...

Neither. These are simply guidelines and can not be as precisely black and white as we might wish. You will soon get a feel for your pool and learn that the guidelines you establish have some wiggle room and that you will develop a sense of how much wiggle room you're comfortable with.

You need to bring your pH down to around 7.4 or so....8.0 is too high.

You also indicate your fountain will reduce FC.....it won't. The FC will have to come down on it's own....usually by about 3ppm daily or thereabouts for your conditions.
 
It was my "feel" for the pool that got me into the position from which I just eradicated myself - a black algae farmer. My first step in giving up the aquatic algae farm was to follow advice here and kill the BA. My second step was to commit to the BBB system and in that spirit I read gobs of stuff here and I purchased a TF-100 so as to have a more precise instrument to fly by and, at least for the time being, move away from the "feel" method that I used to fly myself right into Black Algae Mountain. Now, as I bringing my pool back into the land of the living, I am trying to understand and establish is

1) The difference, on the Chlorine/CYA Chart, between the min FC and the Yel/Mustard Min ?
2) The FC level, with a buffer, at which I should strive to I keep my pool given a) a CYA level of 40 and b) a past history of BA which I understand is "equivalant" to Yellow or Mustard algae ?

My pH is at 7.4 now. TA and CH are in TF-100 kit range. Just looking to understand and establish the proper FC level in accordance with the CL/CYA chart conditions a) and b) above.

As I have read a bunch of stuff lately, was under the incorrect assumption that the aeration that a fountain provided accelerated the FC loss. My bad.
 
1) The "Yel/Mustard Min" column in this chart is a guess at a FC level required to prevent pools which have mustard algae from having the mustard algae become active and spread. If you can really and truly get rid of the mustard algae then that column doesn't mean anything.

A better approach is to completely kill off the mustard algae and then never ever allow FC to fall below the "Minimum FC" level in this chart.

2) With black algae it is more or less the same thing as with mustard algae. If you can't kill it all off, you can maintain your FC level somewhat higher and then at least it won't spread. But you are much better off if you can kill it all off. The exact FC level required to keep it from spreading varies from pool to pool, there is no one number that works everywhere.

The key point is to never allow your FC to fall below the minimum. You can do that by being close to the minimum FC level and very diligent at raising the FC frequently, or by aiming for a higher FC level so that even if you miss a chlorine addition you are still above the minimum.
 
Beginning to understand, I think.

The critical criterion, given I had BA, in determining which chart and consequently which FC level never to fall below is whether or not I THINK I killed it all.

So that I can get a little more clear, let's assume a 40 CYA -

1) If I think I did kill it all, use the "short" chart and never fall below 3. or

2) If I have doubts or am am not 100% sure, use the "long" chart, the Yel\Mustard min column, and never fall below 6.1.

If that is a correct restatement of the decision criterion and a correct read of the respective applicable charts (and I do understand water chemistry is dynamic and is individual pool, area, condition dependent and the #s vary), it seems to me the safer way to go is with 2).

Jason, other than the additional cost of bleach, are there any other factors I should consider or "things" I should watch for or be aware of in going with 2) above and 2X the FC level, given a rough 6.1 FC min with probably a .5ppm buffer for a total of around 6.5ppm FC ?
 
Yes, it sounds like you are getting it. One issue is that FC at 3 has had a lot of testing and is known to work if you don't already have algae. FC at 6.1 to prevent the spread of mustard/black algae is more of a guess, it is somewhere around there but it might actually be 5 or 7 or even 9 in your pool.

If you go with your approach 2, you really have to watch out for unusual events that bring the FC level down. Storms can lower FC, more people swimming than usual can lower FC, missing adding chlorine one day can lower FC. If you go with this approach you have to stay ahead of things and bring the FC level up extra in advance of events that will lower it extra.
 
Thanks a bunch. I really appreciate it.

Is it correct to assume that your caveat of approach 2) is based on my belief that the all the algae may not be dead so therefore I am at greater risk for its return (again, given its assumptive presense) should the 6.5 min level drop and not that the other FC reduction factors - bather load, storms, missed Cl additons, etc don't effect the 3.0 lower min. (1)) equally ? IOW, the same diligence and attention to "extra" factors is required regardless of the chosen min level, correct ?
 
Well, it all depends on the algae :)

If you actually have persistent algae, then keeping it in check requires diligence. If you don't currently have algae then you have some room to make mistakes. If you don't know if you have persistent algae, and are thinking of a higher chlorine level as "insurance", then there are two possibilities. EIther you don't actually have algae, in which case you waste a little bleach (not a big deal). Or you do have algae, in which case you are only safe till you make a mistake and then the algae will come right back again.

Personally I would rather know if I have algae and do whatever it takes to kill it all so that I can relax after that. But there are people who are sick of fighting algae and never winning, who would rather be very diligent than continue a fight that they feel is hopeless.

Hopefully from this you can see why the "Yel/Mstrd Min" column has not be maintained in the newer charts. The general feeling these days is that it is better to kill it all and not to even mention the option of living with algae that is merely held in check. At the same time there is very rarely a situation where the algae is mysteriously persistent and nothing seems to kill it. In those very rare cases the higher "held in check" level makes sense.
 

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Thanks again ! Your logic is clear and you have added another piece to the puzzle.

I do not see any algae, Black or other wise. Believe I have scrubbed off the last remaining visible heads and treated with a triclor puck until they have disappeared completly. My confidence level is 99% that I killed it all while my respect for the heartiness of the stuff is 100%. However I have no way of being 100% certain of its total eradication at this stage.

Having said that, really the most important lesson in this process is that I am 100% responsable for causing (not my pool, the pool store, or mother nature) the condition through lack of knowledge and lack of diligence. I am futher confident that I will make mistakes of knowledge and diligence as I travel the BBB path and my belief that I killed it all will be tested when I do make those make mistakes. Don't know any other approach at this point.

Thanks again for all your help.
 
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