Stumped with my algae situation

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J

John Rock

Well-known member
Apr 10, 2010
110
Montreal, Quebec
Hi,

All summer, I've been fighting some algae, with a few good runs, and have noticed a few things:

- TA is always going down. For example, it can drop from 100 to 80 in less than two weeks. Added way more baking soda then usual this summer.
- PH is always pretty high. Added way more acid this year, perhaps 16L this summer so far.
- Added at least as much liquid chlorine as previous years (at least 120 liters @ 12%)
- My CYA is low purposefully, under 30, since I wanted to try that approach this year and see if chlorine would be more potent
- Shocking my pool to 10+ FC. Doesn't go down drastically overnight, but not measuring any CC. Is that normal? My CC reagent is at least 3 years old however.
- Even when shocked, algae (green color) keeps showing up in same spots (mid-wall on deep end, one corner) after brushing the day before.

Feels like I'm in a chemicals rat race. Should I be always be adding so much baking soda? Is adding so much acid normal? Do I have some special algae that is very hard to kill yet doesn't show up in CC?
 
I want to watch this thread however from what I have learned in Pool School and others on this forum is that the lower the TA the slower the pH rise. You state your pH continues to be high so you add MA to lower it. This also drops your TA. it is indicated in the forum that one should not chase a specific TA number but find a "happy spot"

I copied the below from a TFP article
There are two reasons to lower your total alkalinity (TA) right away, because you want to slow down the rate that the pH rises, or if high TA is contributing to a high calcium saturation index (CSI) which puts you at risk of calcium scaling. You shouldn’t lower TA just to reach a target number. Make sure you actually have one of the above issues before lowering your TA.

The acid/aeration process to lower TA:

  1. Add acid to lower your PH to between 7.0 and 7.2 (this also lowers TA)
  2. Aerate until PH rises to around 7.6 (the only way to raise PH without also raising TA)
  3. Repeat steps 1 and 2 until you reach the desired TA.
 
John Rock said:
Wouldn't the concentration remain roughly the same, regardless of water level? I don't think I have a major leak (some small leaking near pump), but my Polaris cleaner does squirt a lot of water out from the tail, so I do need to top up water level from time to time.
Click to expand...

As water leaks out, the carbonate leaks out too. If your fill water is lower TA than the pool, TA will decline over time.
 
Algae will not always cause CCs. If you're seeing algae on the walls, you need to follow the SLAM Process. As an added measure, you should follow the procedures for mustard algae. It's stubborn and will require you to seek and destroy any remaining traces.

Rising pH can be caused by sources of aeration such as splashing kids, waterfalls, water features, and spillovers.
 
HermanTX said:
I want to watch this thread however from what I have learned in Pool School and others on this forum is that the lower the TA the slower the pH rise. You state your pH continues to be high so you add MA to lower it. This also drops your TA. it is indicated in the forum that one should not chase a specific TA number but find a "happy spot"

I copied the below from a TFP article
There are two reasons to lower your total alkalinity (TA) right away, because you want to slow down the rate that the pH rises, or if high TA is contributing to a high calcium saturation index (CSI) which puts you at risk of calcium scaling. You shouldn’t lower TA just to reach a target number. Make sure you actually have one of the above issues before lowering your TA.

The acid/aeration process to lower TA:

  1. Add acid to lower your PH to between 7.0 and 7.2 (this also lowers TA)
  2. Aerate until PH rises to around 7.6 (the only way to raise PH without also raising TA)
  3. Repeat steps 1 and 2 until you reach the desired TA.
Click to expand...

So perhaps I'm doing it wrong. I thought I needed to reach a TA target level first, say 120, then adjust PH, then add chlorine and try to keep everything at the right levels.

To confirm, I was never trying to lower TA, but increase it since it's always falling towards the 60 range while I'm trying to keep it at 100+, thinking that this will help me stabilize PH levels and keep them lower, making my chlorine more potent.

Wondering how to start over now, besides keeping my chlorine at shock level.
 
Rancho Cost-a-Lotta said:
Algae will not always cause CCs. If you're seeing algae on the walls, you need to follow the SLAM Process. As an added measure, you should follow the procedures for mustard algae. It's stubborn and will require you to seek and destroy any remaining traces.

Rising pH can be caused by sources of aeration such as splashing kids, waterfalls, water features, and spillovers.
Click to expand...

Good to know algae won't always produce CC, thanks! Perhaps it is mustard algae since it's growing at 8-10+ FC levels with little CYA in the pool.
 

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John Rock said:
So perhaps I'm doing it wrong. I thought I needed to reach a TA target level first, say 120, then adjust PH, then add chlorine and try to keep everything at the right levels.

To confirm, I was never trying to lower TA, but increase it since it's always falling towards the 60 range while I'm trying to keep it at 100+, thinking that this will help me stabilize PH levels and keep them lower, making my chlorine more potent.

Wondering how to start over now, besides keeping my chlorine at shock level.
Click to expand...
That is why I copied the article on lowering TA. I was unsure why you were trying to increase it to 100+ while recommended levels target a lower TA to help stabilize pH. I am learning as well which is why I wanted to follow your thread. Good Luck.
 
HermanTX said:
That is why I copied the article on lowering TA. I was unsure why you were trying to increase it to 100+ while recommended levels target a lower TA to help stabilize pH. I am learning as well which is why I wanted to follow your thread. Good Luck.
Click to expand...

Thanks for that. I hadn't looked at Pool School for a while, but I could have sworn that target levels where 100-120. So I guess the TA problem is solved! :)
 
John Rock said:
So perhaps I'm doing it wrong. I thought I needed to reach a TA target level first, say 120, then adjust PH, then add chlorine and try to keep everything at the right levels.
Click to expand...

I would say the exact opposite. If you have been battling algae, your #1 priority should be chlorine. Have you done a SLAM to get rid of the algae?
 
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Update: I've been keeping at it at the water is pretty clear, not crystal yet. Yesterday, I stopped the Polaris to see if the algae would reappear and sure enough, I'm seeing some algae starting to show up in the same places. This is maddening. Do I need to crank up the FC level to 15+? I'm concerned this will start bleaching my vinyl.
 
Here are fresh results (added more chlorine last night):

FC = 13
CC = 0
PH = 7.9
TA = 80
CYA = less than 30 (only used a few pucks during the summer)

Note that it's getting cold up here and I usually close the pool in November after most of the leaves have fallen. Am I wasting money trying to fix this now VS when opening the pool next spring?
 
What was your FC level before you added more? Are you keeping it high enough between additions of chlorine. I'd clean it up now when the algae is easier to kill rather than open to a green pool in the spring.
 

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