adjust cya before or after shocking

[chem geek]

Is your vinyl liner blue? If so, then I think you may have yellow/mustard algae and not green algae. Yellow+Blue(cyan) = Green. You describe the algae as "dust" which sounds more like yellow/mustard algae and would explain why the usual chlorine maintenance levels aren't keeping it away. Is the algae mostly on the wall and floor in the shady area of the pool? Yellow/mustard algae prefers shade. Do you have any removable ladders or other equipment in the pool where the algae might be hiding out inside? For plaster pools, we have people go behind light niches where they often find a lot of yellow/mustard algae if they have such an infestation, but I don't think you have pool lights (and therefore light niches) in your vinyl pool, do you? Is the algae in areas of poor water circulation?

Also, are you sure that it's algae and not pollen?

[Kateyru]

Yes, liner is blue. as i said on other thread, algae seems to disappear in the direct sun tho I think there is almost always a yellowish band of ??? algae (or a stain) where the wall and floor meet in several areas around the pool...if that makes sense. I have a ladder, not sure if it's removable as I've never tried to take it out. I have 1 pool light. How do I identify areas of poor water circulation? I'm fairly sure it's algae and not pollen.
Just read section on mustard algae, and I think you're absolutely right...that's the problem! No wonder my efforts were not enough. Sounds like a major production to get rid of mustard algae.
Many, many thanks!!!

[Kateyru]

Just realized that I posted a response on the other thread so left out some info here. CYA was about 65 on 5/30 so my shock level is now 20, correct? I'm going with the mustard algae theory so will shock at 20 till FC loss is < 1 ppm. Hoping that is done today (I was out of town all day yesterday and couldn't do much). When that's done, I'll move to super shock to get rid of mustard algae and will keep FC at or above 35 to 40 for 24 hours, correct? I've got to figure out how to get light out of pool. Can I put robotic cleaner and cloth bag, rubber mat (float) and nylon recliner floats in pool for 1 hour (in super shock) or is it better to clean with bleach solution? Also, instructions say to wash bathing suits. Do I need to use bleach with suits?

[Kateyru]

If I can't get light out of pool, is super shocking all for naught???

[Kateyru]

Help! On 5/30 at 9pm, I figured out that I had mustard algae...thanks to you guys and I went ahead and added several qts. of bleach that evening to start usual shock process planning to go to mustard shock after that, per website instructions. On 5/31 at 7:30 am, FC = 22.5 and I thought the CYA = 65 so I understood shock to be 20. I kept FC over 20 on 5/31 until I tested at 7:30 pm and FC was 16.5 I kept FC > 20 on 6/1 and lost 2.5 ppm of FC overnight and was at 19 at 7:30 am on 6/2. Got FB back over 20 on 6/2 but lost 2 ppm overnight so FC = 18.5 at 7:15 am on 6/3. Got FC > 20 all day on 6/3 but lost 2.5 ppm overnight again. This morning, at 6:30 am. FC = 22. I decided I needed to recheck CYA this morning, and it now looks to be 50. I had just added CYA (through sock) on 5/31 and got the higher reading.
So, does CYA settle down after being added? Why do I keep losing > 1 ppm of FC overnight? I was hoping to move to mustard shock today but guess I'm not done with regular shock yet. Please advise. Thanks!

[BigDave]

CYA doesn't settle, you usually lose it by splashout or backwash. A drop of 65 to 50 may just be the accuracy of the test.

[CarlD]

CYA doesn't settle, you usually lose it by splashout or backwash. A drop of 65 to 50 may just be the accuracy of the test.

In other words, by dilution. But try to always run the CYA test the same way. One trick I use is to pour it back into the squeeze bottle and run it again (it doesn't change the solution to do this). Sometimes I do it three times, always trying to do it the same way. This helps me neutralize errors in any one of the readings, and I'm not using any more reagent, just reusing the sample.

[PoolDoc]

Katey,

This thread has gotten VERY long and hard to keep up with. Could you please enter your pool info here:

Pool Chart Entry Form
Pool Chart Results

. . . and log your test results, here:

Pool History Entry Form
Pool History Logsheet

That would make it MUCH easier to keep up with what's going on, and give an intelligent response. I'm going to go back and put in the first couple of test results you have, but if you'd do the rest, and any new ones. The short URL for your test results is http://goo.gl/6ok5j and I'm adding that to your signature.

Thanks!