Is Mustard Algae Shock level safe for a vinyl liner?

[rljml]

I have a 27k-28k gallon pool with a SWG and for the first 5 years was trouble free. Since last year, we have had recurring algae blooms and from what I have read on this site, I seem to think it must be mustard algae. We had our sand changed last year and everything was fine during the winter but as soon as the water started to warm, our problems began again. Pool chemistry is as follows:
FC 2.1
TC 3.0
CC 0.8
pH 7.2 (I lowered it in anticipation of shocking)
CYA 75
Hardness 300
Alkalinity 108
Salt 3000
A week ago, there was yellowish green tint to the water and when I brushed, it "poofed" into a cloud. The pool is now a nice dark shade of green.

Assuming this is mustard algae, chem geek's table calls for a shock level of approximately 43 ppm.

This may be an uninformed question, but anyway: Is this safe for a vinyl liner?

Second, How long do I need to keep my shock at this level to rid myself of this scourge? Many thanks for the help.

 

[duraleigh]

This may be an uninformed question, but anyway: Is this safe for a vinyl liner?

Second, How long do I need to keep my shock at this level to rid myself of this scourge?

Of course, it's safe.

read "How to Shock Your Pool" up in Pool School. You will find that the process involves a very distinct sequence of tests and results before it is complete.

 

[chem geek]

Welcome to TFP!

It's safe because it's the active chlorine level (which is related to the FC/CYA ratio) that is relevant, not the FC alone. Also, low pH is far more harmful to liners than even a high active chlorine level. The yellow/mustard algae shock level has the same active chlorine amount as a pool with 1.5 ppm FC and no CYA.

 

[linen]

Welcome to tfp, rljml

Second, How long do I need to keep my shock at this level to rid myself of this scourge? Many thanks for the help.

Here is the link to defeating mustard algae: http://www.troublefreepool.com/pool-school/mustard_algae. Since you already have measurable CC levels make sure you follow the link in that article to do the normal (lower FC level) shocking process first.

Let us know if you have questions.

 

[rljml]

Many thanks all. I have spent hundreds of dollars at the local pool stores and have ZERO to show for it...I take that back...I have a nice green pool that is perfect for our south Louisiana habitat. I will keep you all posted. Thanks again for the help.

 

[rljml]

I do have one other question: Step 3 states I need to keep FC at shock level until: CC is 0.5 or lower; overnight FC loss test shows a loss of 1.0 ppm or less; the water is clear.

In terms of the FC loss, I'm assuming I need to turn my SWG OFF and rely only on liquid chlorine in order to properly measure/monitor FC levels.

 

[Bama Rambler]

That is correct. Make sure you turn it off.

 

[chem geek]

I would not do a yellow/mustard algae shock level unless you actually have yellow/mustard algae. If your pool is green, then you probably have ordinary green algae and that does not need as high a shock level. Yellow/mustard algae looks like dust that is easily moved away and tends to form on the shady side of the pool. It isn't nearly as common as green algae.

 

[rljml]

I'm not positive what I have but here's what I've seen: 1) it's yellow on my white steps (assuming not pollen), 2) It "poofs" into a cloud when I brush, 3) It grows on the sides of the pool - all sides not just shady, 3) My water was initially a yellow green (but it is now over a week and is a dark green), 4) I have shocked and treated according to pool store recommendations several times and it continues to come back when my FC levels drop, 5) I have made sure all pool items have been in the pool to ensure they get treated as well, 6) My pool used to be literally trouble free and now is a source of constant angst. Whatever I have is a scourge and have assumed it must be mustard algae.

 

[duraleigh]

rljml,

Your description of your pools condition certainly seems like you have mustard alage...probably the green stuff, too, but mustard algae nevertheless.

I would shock at mustard algae shock value until the pool is clear Get your pH in the low to mid 7's first and then start the shock process. Follow EXACTLY the directions in the article in Pool School and your pool WILL be crystal clear. :lol:

 

[zea3]

Hi rljml, could you edit your signature line to include info about your pool size, liner, pump size and brand, and filter size and brand.

 

[chem geek]

Don't forget to get behind light niches and under removable ladders (if any). If it's yellow/mustard algae, it really likes to hang out in such shady areas of low circulation.