recurring mustard algae despite high FC

[RAS]

I keep getting mustard algae (MA), despite the fact that after my first instance of MA I keep FC relatively high (8.5+) compared to the level on the SWG section of the Chorine/CYA Chart on this site. I maintain pH 7.5-7.8, CYA 60-70, TA 60-80, CH ~300, salt ~ 3100. I've read posts that say CC is not indicative re mustard algae, but in any case CC tests consistently read 0.

When MA does occur, I faithfully follow the SLAM procedure. Usually FC is around 10 and I don't think MA has bloomed at that level or higher, but each time FC dips to around 8-8.5 MA develops.

According to the "It hurts when I do this" -- "then don't do that" advice, that I should therefore keep FC at 10 above, that level seems excessive according to all wisdom I see, so does anyone have any idea why this is happening and what I might do about it?

Thx in advance ...

 

[RAS]

One additional point in case someone might think it be relevant to this MA problem: I use the IntelliFlo variable-speed pump to cut my electrical cost (it's paid for itself). Specifically it runs at a relatively high rate for the one hour per day that I also run the booster pump to drive the Polaris 380 cleaner. I tell the IntelliFlo to do 1 turnover per day, just fast enough to the SWG from cutting off. In all, it's circulating for about 9 hours per day to achieve that single turnover.

 

[Pool Tool]

I think this is more a function of not thoroughly completing the SLAM. As the chlorine level drops to the recommended FC levels, it can not kill the reproducing algae quick enough which turns into a bloom. I would wager that with enough time, algae would still be visible even maintaining FC at 10. Mustard algae can be difficult to kill. I would go back on SLAM then follow the Mustard process and once "passed" hold it there for 1 additional day. Be very critical of your testing and OCLT. Be sure to either throw all the pool toys in with the SLAM or wash independently. Brush out and light niches, ladders, etc. where algae can hide.

I have done this myself before and thought I was out of the woods but having it return because it wasn't completely eradicated. Good luck.

 

[RAS]

Pool Tool, many thx for your thoughts. I'm pretty sure I completed the SLAM, including the extra boost of Cl to Mustard Algae levels as in http://www.troublefreepool.com/threads/2177-Chlorine-CYA-Chart but I probably will add an extra day this time.

I will say, though, that it's hard (nearly impossible?) to scrub all surfaces. E.g., the undersides of the channel to the skimmer. And doesn't that mean that the inside of the filter canister should be scrubbed? In fact, the inside of all the piping? I'm honestly not trying to be sarcastic here; my real point is that if every surface needs to be scrubbed and that if getting the FC level high enough alone can't kill all MA, then it all seems hopeless. So while I brush accessible areas my hope is that ultimately getting FC high enough can be sufficient.

A couple other comments, though, for you or whomever else may be following this and for the web-site maintainers:

1. I interpret the "Yel/Mstrd Min" column of the above-referenced page to mean the minimum FC we should maintain to avoid MA. And if that's the case, then my original post in this thread was wrong when I said that it doesn't seem that the FC dropping to 8-8.5 should be allowing MA as it seems this chart is saying that for CYA of 60-70 we need to maintain FC at 10.5 or higher! Whereas I'd been assuming from http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock that by keeping well above a target FC of 6 for my SWG pool I'd be safe.

2. If I'm correct that in fact I should stay at FC 10.5 or higher, then I really suggest that the page I just referenced really should have a note saying that target FC will not be sufficient to avoid MA. Or, add another column which is target FC to avoid MA.

3. A question about measuring CC: I asserted that my FAS-DPD test for CC said zero, which it did at first. But rather than immediately washing out the vial as I usually do, I stopped for lunch and upon return saw it had turned pink. So I added another drop of 0871, it went clear, and I waited 10 minutes after which it was slightly pink again. Repeating this, it appears CC might be 1.5. Then I reverted to just measuring FC to see if the same issue might be true there, and indeed after a wait the solution that had been previously clear was slightly pink.

So my question is, what's the valid way to test? Does the FAS-DPD test for FC and additional R-003 test for CC give immediate results, or does accurate measurement really require waiting a period of time. [In case anyone questions whether the initial tests weren't stirred well enough, I use a SpeedStir and the little magnetic bean spins it's heart out, so I can't believe that that bean in just 10 ml of liquid doesn't produce a nearly immediate adequate mixing.]

Thx in advance for any response.

 

[pooldv]

1. Yes, that is the min to avoid mustard algae if your pool is prone to it. I would keep it at 9 sometimes, or at least let it drop to 9 so you can test PH since the pH test isn't valid when FC is above 10. It is safe to swim up to shock level for your cya, [FC/CYA][/FC/CYA]

3. The FAS/DPD test will always turn pink again after a while. The test is complete as soon as it turns clear or if it remains clear when adding 0003.

 

[RAS]

1. Yes, that is the min to avoid mustard algae if your pool is prone to it. I would keep it at 9 sometimes, or at least let it drop to 9 so you can test PH since the pH test isn't valid when FC is above 10. It is safe to swim up to shock level for your cya, [FC/CYA][/FC/CYA]

3. The FAS/DPD test will always turn pink again after a while. The test is complete as soon as it turns clear or if it remains clear when adding 0003.

Both statements are good advice. THANK YOU!

 

[duraleigh]

Don't stretch out any of the tests.....you are asking them to fail.

Do the FC test, record your result, then do the cc's test.....maybe one minute (or two) from start to finish. easy peasy.

Thousands of pools get rid of mustard algae by simply following the steps in the SLAM article and FC/CYA charts. If your pool chooses to be troublesome, you have no real choice other than to up the FC level maybe around 10 ppm and brush, vacuum more regularly.

The science behind what we teach is rock solid. The solutions are simple but don't always fit into a neat little pattern.

You will soon discover what your pool wants to stay pristine. Give it what it needs and enjoy it!

 

[RAS]

1. Yes, that is the min to avoid mustard algae if your pool is prone to it. I would keep it at 9 sometimes, or at least let it drop to 9 so you can test PH since the pH test isn't valid when FC is above 10. It is safe to swim up to shock level for your cya, [FC/CYA][/FC/CYA]

3. The FAS/DPD test will always turn pink again after a while. The test is complete as soon as it turns clear or if it remains clear when adding 0003.

This leads to additional thoughts which I'll mention just so someone can point out the error of my ways if I'm wrong:

1. I am this time, as recommended further above, going in the latter part of the SLAM to deal with Mustard Algae, boosting FC to substantially higher than shown in http://www.troublefreepool.com/threads/2177-Chlorine-CYA-Chart (50 vs the 34.9 indicated for my CYA of 60). However, I'll still consider the pool prone to MA so will maintain a higher FC in steady-state. But if I maintain my CYA of 60, then FC will need to stay above 9 where advice is that pH readings become questionable. Yet then dipping FC to 9 or below to get a decent pH reading then opens the door a bit for a MA bloom.

Therefore, it seems to me that it would be smarter to maintain a lower CYA, like 40 or 50, so I can keep FC around 9 but still safely above the Yel/Mstrd Min of 6.1-7.5. The downside of that is that with the lower CYA I may need to boost my SWG to compensate for greater FC sun loss, which means shorter SWG cell life. Accepting the fact of potentially shorter cell life, is this plan, keeping a lower CYA, at least sensible?

2. A related topic driven by the above question: Lower CYA means needing to generate more FC, but then greater CYA requires more FC as well because (as I understand it), higher CYA leaves a lower proportion of FC being effective. So it seems to me that if one plotted the effect of CYA on both FC loss-rate and FC 'effectiveness', there should be a likely 'sweet-spot' for whatever the target usable FC is. Has anyone done this? If not, can anyone cite the exact relationship CYA-versus FC-loss-rate and CYA versus FC-effectiveness?