TA high, crazy scaling in just 1 day

Problems relating to pH and total alkalinity.
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TA high, crazy scaling in just 1 day

Postby Guest » Tue 28 Aug, 2007 12:06

TA 250, PH 7.8-8.0, Cl 3.0 ppm, hardness 200ppm, salt water pool 19,000 gal

Goal...elimanate scale and lower TA

THe water were I live is hard but I used sequ-sol to adjust water hardness from 400ppm to 200ppm. After running my waterfall for about 10 hours there is a tremendous amount of white scale all over the front of the waterfall. I have had pools in the past and the amount of white build up I have after one day looks like a year or two of build up in one day! Adjusting hardness has helped but scale is still really bad. I only get the scale on the parts of the waterfall where running water is and no where else in the pool. I have read that high TA can cause scale :shock:

I am trying to adjust my TA down to 100 by adding MA (added 2 gallons in last 24hours). .

I have read the topics on here to lower TA but am worried about using my waterfall to aerate. any suggestions. I live in Woodland Ca
:shock:

Best,
Justjabbin


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Postby justjabbin » Tue 28 Aug, 2007 12:09

I posted this but I was not logged in...sorry!
Best,
Justjabbin
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Re: TA high, crazy scaling in just 1 day

Postby Backglass » Tue 28 Aug, 2007 12:24

Anonymous wrote:I have read the topics on here to lower TA but am worried about using my waterfall to aerate. any suggestions.


Anything that bubbles would also work. Do you have an air compressor?
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Postby justjabbin » Tue 28 Aug, 2007 12:39

I might be able to borrow one...just put it in the deep end? Any suggestions on the scale?
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Justjabbin
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Postby chem geek » Tue 28 Aug, 2007 19:07

Aeration from the waterfall would cause the pH to rise and that is causing scale (given the other parameters of TA and CH). You want to lower the pH FIRST before starting the aeration and you want to keep adding acid when the pH rises to keep it LOW since that will prevent scaling.

If you lower the pH to 7.0 and keep it below 7.2 while your waterfall is aerating, then you should be fine. At a pH of 7.8, TA of 250, CH of 200, your saturation index was +0.6 which is around when scale can start (and at a pH of 8.0 it's +0.8 and where the aeration occurs the pH would be even a little higher). At a pH of 7.2, on the other hand, the saturation index is only 0.0 which should not lead to scale even on the waterfall.

As your TA goes down while you are still keeping the pH low, then the existing scale on the water could dissolve somewhat. Otherwise, it'll have to be treated explicitly with a dilute acid wash. So, you can turn off the waterfall if you get a separate aeration device until your TA gets low (closer to 100) and then turn on the waterfall with the pH still at 7.0-7.2 and the scale should dissolve (and you can brush it to help it along).

And clearly, your waterfall is such a good aeration device that you can't leave it alone for too long or else the pH will rise too high (at least until you get the TA lower).

Richard
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Postby justjabbin not logged in » Tue 28 Aug, 2007 22:10

Thanks Richard... In your opinion is the high TA a likey candidate for the scale on the waterfall?

What do you recommend as a dilute acid wash?

Once ta is Lowered to 100 do you recommend keeping ph at less than 7.5 to minimize scale?

Best
Justjabbin
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Postby fatybabe » Tue 28 Aug, 2007 22:37

Hydrochloric acid
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Postby chem geek » Tue 28 Aug, 2007 22:46

In your particular case, it was the combination of high TA with high pH that caused the scale (the CH wasn't too high).

The previous post from (can't put in fa...be name since it thinks it's some sort of link) already answered the question as to the acid -- it's just Muriatic Acid (which is 31.45 % Hydrochloric Acid) diluted, but I don't have personal experience with decent dilution rates for removing scale so others will have to give you their recommendations on that. I would first try removing the scale towards the end of the TA lowering procedure since the TA and pH will be low at that time and might be enough to remove the scale with some brushing (but I don't know for sure).

Yes, once the TA is lowered, try and keep the pH certainly below 7.7 which should be easier to do at lower TA. The main cause for pH rise is high TA.
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Postby justjabbin » Wed 29 Aug, 2007 00:20

THanks to all who have responded!
Best,

Justjabbin
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Postby justjabbin » Wed 29 Aug, 2007 00:22

To get my PH down to 7.0 I calculate I need to add approx 3 gallons of acid. I added one gallon today...can I add 2 gallons tommorrow or should I add one gallon a day? pool approx 20,000 gallons
Best,

Justjabbin

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