Confused & need help with algae

[jtjneff]

I have been having a problem for past 3-4 weeks with dark green algae buildup on very shallow sun shelf. Water has remained clear. Pool is in full sunlight all day. I have read Pool School, but can't say I understood it all (yes, I'm feeling kind of stupid). I have a new TF-100 Test Kit. Just completed all tests and readings are as follows:

FC=1.5
CC=0
TA=120
CH=380
CYA= too low to register (dot stayed visible)
Salt =3830

I realize I need to shock the pool. (BTW, I've been adding a bleach bottle or two a day for past week trying to keep chlorine level up to normal until this test kit arrived today. I did not add any bleach today so chlorine has again fallen).

I am feeling confused as to what my target shock level should be with no CYA. Or should I add CYA and get that level to 70-80 before beginning shock process? It says it can take up to a week for CYA to register on the test. I would like to get this under control ASAP, but I'm not clear as to how to begin (and also feeling like I really don't quite "get" it).

Any help is greatly appreciated.

 

[Vette]

With an SWG, you really need CYA. You can shock now at 0 CYA because shock level is lower, but as soon as you pass the criteria to finish shocking, add CYA.

You may want to run the CYA test again. In the 3 years you've had it, have you ever used Trichlor, drained the pool, or added CYA (stabilizer)

 

[jblizzle]

Welcome to TFP!!!

Likely your problem is due to the sun breaking down most all the FC that the SWG can generate since your CYA is so low.

It is best to boost the CYA up to 30-40ppm to protect the FC from the sun.
What is the pH? Adjust it before the next step.
Then follow the shock process.
After passing the 3 tests, raise the CYA up to 70-80ppm and dial in the SWG.

You can use the poolcalculator to calculate how much stabilizer to add. Once it is in the water, assume that it is working even though it is not on the test yet.

Feel free to ask questions as they come up.

 

[Vette]

Yes, you need to test PH as well. In the TF-100, its the Taylor Basic kit in the blue box.

 

[jtjneff]

Sorry I left off PH - it's 7.6

My husband has used Stabilizer very infrequently in past (maybe 2/year). We've had no visible problems with pool before now so we've never had to do much other than add muriatic acid monthly & salt twice a year since it was constructed. We've been flying blind for a while (too long I guess).

I do have some Stabilizer (which I just recently learned is CYA!) and I will add it tonight using pool calculator to determine dosage.
Thank you all very much!!!

 

[jtjneff]

Thanks for your help. I do have a few questions though.
I am on day 2 of shocking pool. Yesterday the Pool Calculator suggested adding 11 large bottles of bleach to bring FC up to 10 (recommended shock level). After I added 2 bottles I checked FC and it was already up to 12.5 so I didn't add any more bleach (??? I don't understand that - 2 bottles vs. 11 seems like a huge discrepancy). Anyway, last night after sundown the FC was down to 11 and CC was at .5 so nothing else was added.

Early this morning my FC was at 8.5 so it's losing FC overnight which is good I guess because it's fighting the algae. But there was no CC reading (CC=0). I would assume if chlorine were destroying algae wouldn't there be a CC reading? Is that how it works?

I have added another bottle of bleach (182 oz) and now FC is up to 16.5. Again, pool calculator seems wrong - it told me to add 513 oz to get back to FC of 10 & I only added 182 oz. and reached 16.5! I don't know if I'm using the calculator incorrectly or what. I've plugged in my numbers & have double & triple-checked it all. Please let me know your thoughts.

 

[Vette]

If the chlorine and sun oxidize CCs fast enough there will be none. Is that 12% or 6% bleach?

 

[jtjneff]

I'm using regular 6% bleach.

 

[jtjneff]

Okay, I guess I'm really an idiot! I just realized I had an extra 0 in the pool size box! No wonder it was all off.
I'm so sorry!
So I think I'm on the right track.
-and I won't worry about CC reading of 0. Thank you!

 

[jblizzle]

Re: Confused & need help with algae

the pool size would have been my suggestion to check ... common problem ... glad you caught it.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[jtjneff]

Just wanted to let you know that after 20 bottles of bleach & keeping FC at shock level for 6 days, my pool has never looked better. My numbers are looking good (still working on getting CYA up). Visible algae was gone on 3rd day but overnight readings told me to keep shocking for 3 more days. Water looks great. I just thought I had clear water before - but this is crystal clear & sparkling! Thank you for your help & for your website! I now feel MUCH more confident about taking care of this pool.

 

[dattia]

Knowledge is power! Just adhere to what you have learned and your pool will always be that way. Congrats!