How long should it take to clear black algae

[PoolDoc]

It's possible that you still have oxidizable residue in the pool -- chlorine + UV will oxidize things that chlorine alone may not. I would recommend the following:

#1 - do a stabilizer test on a 1:1 dilution of your pool water with tap water. (Fill a cup measure to 1/2 cup with pool water, add tap water to 1 cup, mix and test that as your sample.) Please check the test instructions, and make SURE you are doing the test correctly.

#2 - Assuming you confirm your CYA reading, add a SHOCK dose of chlorine, in the evening, using the Best Guess table to determine the correct dose.

#3 - Test this dose the following AM, and PM, and let us know the effect, if any.

#4 - Then, maintain a NORMAL chlorine level for your CYA level, again referring to the B-G table.

If your CYA is anywhere near 100 (or above), 1.5 ppm is not nearly adequate to oxidize goo in the water. Also to the best of my knowledge, even with very high stabilizer, once you have removed most of the 'goo' from your water, much of the chlorine consumption will occur in the day, as a result of photolysis AND UV enhanced oxidation of contaminants.

[joecus]

I don’t see my post, so I re-wrote it. Sorry if it comes twice.

Thanks Ben.
Hello everyone. I did the 50/50 tap water cya test and the black did not disappear. I will shock tonight and report in the morning. I do have a few basic questions;

1. Once the pool is stabilized, will I use more bleach than someone with a low cya? I understand it will take more initially, it’s after that point I’m not sure about.

2. Once stabilized, when is the best time to check/add bleach each day?

3. Any thoughts on what the bad smell is? How do I treat?

4. What is your best guess estimate on my daily bleach consumption, I under stand it’s just a guess-timate? My pool is a 12k in-ground vinyl and has sunlight all day? If it’s going to be more than 1 gallon per day, I think it’s best to do a few partial drain/refill now and get it done, do you agree?

5. If you agree with the drain/refill plan, how many times should I do it, and how much do I let out per drain/refill.?

Thanks everyone, sorry for the basic questions.

[PoolDoc]

OK, you've got two inconsistent test results.

In post #43, you report "the black dot did not disappear". That means a CYA level of LESS THAN 40 ppm. But, in post #41, you report a CYA level of 100+, which means that your dot should have disappeared, when using the 50/50 mixture, at a level of 50 or MORE. So, the first result is that your CYA is MORE than 100 ppm, but your second result is that it's LESS than 40 ppm. One, or both, of your tests are in error.

So, please test AGAIN, with straight pool water, and tell me what you have. Please, PLEASE re-read the instructions, and make certain you are performing the test correctly.

[joecus]

I am so sorry, I really did mess up in the tap water test, yesterday. I did both tests again. The results make better sense.


The cya is 100+ on the pool water only.
The diluted cya is 80.

I shock the cl up to 30 ppm last night around 11:30 pm
This morning,at 8 am, the cl level is very close to 30, down maybe 1or 2 ppm

I assume the high cya is very bad and need advice on how to proceed.

Any thoughts on the smell?

Again, I’m so sorry, Joe

[PoolDoc]

There's a good chance the smell is unoxidized -- or incompletely oxidized -- organics, and that it will be taken care of with 30 ppm FC + sunlight, even with a CYA=160. You'll have to wait to see, however.

Regarding the high CYA, it's definitely thought of as super-bad, but I'm gradually coming to the opinion that it's just different, and requires a different approach to pool care. It certainly has benefits: for example, at 30 ppm, if your pool has no algae, you can probably wait a week before you need to chlorinate again. Obviously, this has real benefits when you are planning to go on vacation.

I've got to go -- I'll have to get back to you. But the bottom line for today is, "Hold the high chlorine and see if it and sun resolve your problem".

[joecus]

Thanks Ben - OK, If you decide I should do a partial drain/refill, I'm ok with doing it.

[PoolDoc]

Let's see what the high chlorine and sun will do, and then explore the alternative between drain and refill vs. operate as is.