Right Chemistry and Still Algae

[BNomad]

I have an Above Ground 8k+ gallon pool, with a DE filter. Chemistry specs as follows:
TFC: 5.5
CC: 0.5
Ph: 7.7
CYA: 40
I keep my 2-speed pump running 24/7 on low.

And yet, I am having an algae bloom that seems to be getting more and more dramatic. My chemistry is balanced, so why the algae bloom? I JUST replaced my liner a few months ago due to an algae bloom that got out of hand and created scale that made it extremely rough all around. I’m trying so hard for that not to happen again. Please someone help!!!! What am I missing? I vacuum to waste and the algae is back next day. The only thing I haven’t done yet is change the DE media in a few months, which I plan on doing in the next 2 days. I’m completely at a loss. Is there something else I should be considering besides the filter media?

 

[PoolStored]

Welcome to TFP!!!

The only cause for algae is allowing your FC to get too low for your CYA...only takes a short period of time.

How/when/how often are you testing your water?

Target FC for your CYA is 5-7. I would run 7-9 in the future. Always follow this and run so that when you TEST, you are never below 7...Link-->FC/CYA Levels

Algae cannot live without light, so it is not the filter.

With visible algae, time to SLAM. Follow the SLAM process to get rid of the algae. Link-->SLAM Process

Don't forget to take the ladder out and clean/scrub INSIDE and out with 10:1 water:bleach solution.

 

[BNomad]

Thank you very much for the helpful advice. I will start the SLAM process tomorrow. To answer your question I use the TF-100 kit, and I test daily or every other day. Generally I don’t allow my CYA to get above 40, but a lot of the time my PH gets up into the low-mid 8’s and it will stay there (I use a digital ph meter for quicker and more accurate results). This is always when I run my pump at the higher speed and it stirs the water a lot. So then I have to use Muriatic Acid to bring it back down quicker in addition to lowering my pump speed. So I know that’s something I need to be careful with. And yeah, solid advice about the ladder. I’ll remove it this weekend for the winter. It’s just not hot enough anymore that the pool is not likely to be used. Even here is central California. Thank you for your help.

 

[reggiehammond]

pH changes are driven by your TA; you don't report it in your testing numbers so what is it?
As TA causes pH to rise, you don't need to change your pump speed. Just dose down with muriatic acid as you've been doing until your TA reaches it's happy place and your pH rise will cease.

How do you chlorinate?

 

[BNomad]

pH changes are driven by your TA; you don't report it in your testing numbers so what is it?
As TA causes pH to rise, you don't need to change your pump speed. Just dose down with muriatic acid as you've been doing until your TA reaches it's happy place and your pH rise will cease.

How do you chlorinate?

My TA was 75ppm when I tested it 2 months ago. My understanding was that for an above ground Vynal liner pool, it wasn’t as crucial to monitor daily or weekly like the others. Unless I’m mistaken.

I do like and need to run my pump at higher speeds from time to time in order to get all the bugs, pollen and small bits filtered out that a net won’t gather. But generally it’s ran at low speed.

I’m chlorinate using 10% liquid chlorine from Home Depot. I will occasionally use Dichlor powder if I’ve done a vacuum to waste and need to bring up my CYA.

 

[joelans]

You're TA at 75ppm is on the high side, which is why you are getting a lot of pH increase. You can get that down to the 60-65 ppm range, and your pH will be lower and more stable. As mentioned, you need to SLAM your pool to get rid of the algae. Once you get rid of the algae issue, keep your Free CL2 no lower than 5, and I would shoot for at least 7 at your CYA. You may consider increasing your CYA a little (to 50 ppm), and then increase your Free CL2 to 6-8 ppm (and with your algae issue, shoot for 8 ppm). Remember, Dichlor powder has CYA in its, but liquid CL2 does not. Once you get your numbers stable, including pH (and get rid of algae), you should be able to get by to testing 1-2/week.

 

[reggiehammond]

My TA was 75ppm when I tested it 2 months ago. My understanding was that for an above ground Vynal liner pool, it wasn’t as crucial to monitor daily or weekly like the others. Unless I’m mistaken.

I do like and need to run my pump at higher speeds from time to time in order to get all the bugs, pollen and small bits filtered out that a net won’t gather. But generally it’s ran at low speed.

I’m chlorinate using 10% liquid chlorine from Home Depot. I will occasionally use Dichlor powder if I’ve done a vacuum to waste and need to bring up my CYA.

You're likely thinking of calcium (CH) - which is not something to worry about in a vinyl pool.
You should monitor pH weekly, preferably more than once. Test TA at the same time, as the TA relationship to pH is easy to understand.

If your TA is higher than equilibrium, then your pH will rise. Each acid addition lowers pH and TA at the same time, so as long as you're not adding more TA, you should see pH rise essentially stop. Any pH in the 7's is ok.