TA high, crazy scaling in just 1 day

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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:

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Justjabbin


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Postby justjabbin » Tue 28 Aug, 2007 12:09

I posted this but I was not logged in...sorry!
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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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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?

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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!
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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
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Postby fatybabe » Wed 29 Aug, 2007 01:21

one a day introduce once the stuff gets settled in you can bee too ahsty with these things.
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Postby justjabbin » Wed 29 Aug, 2007 16:00

Any idea of how much TA will be reduced after each round of acid/aerate?

Also I have 2 tester kits. They are giving different TA measurements from the same water sample.... After first round of acid/aerate my first kit read 230ppm. My second kit read 270ppm. I am just going to take the average of the two. Does this make sense or should I do something different?

Is it normal for a discrepancy of this magnitude between 2 kits?
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Postby chem geek » Wed 29 Aug, 2007 18:56

I just noticed you said (in the first post in this thread) that you had a salt water pool. So you have a salt water chlorine generator (SWG) and you have a salt level of around 3000 ppm? That should actually have somewhat less scaling (the higher salt level allows for more calcium carbonate to be in the water), though would have an even greater tendency for the pH to rise. Essentially, an SWG provides lots of aeration due to the hydrogen gas bubbles (you can see them readily at night if the pump and SWG are on and you turn on the interior pool lights).

When I last answered this sort of question, I was told (legitimately) that I was scaring pool users. The alternative of doing a partial drain/refill was suggested instead, though that only works if the TA of the fill water is low.

As for your inconsistent results, no that is not normal. Are these both drop tests, or are they test strips, or a mixture? The drop test should be more accurate than a test strip. I strongly suggest you get a Taylor K-2006 test kit from Taylor here or from Leslie's here or from poolcenter(dot)com here or the even better TF100 test kit from tftestkits(dot)com here.

Starting with a TA of 250, pH of 7.8, I calculate it should take 162 fluid ounces (20.3 cups or 1-1/4 gallons) to get to a pH of 7.0

I calculate that after the above, it will take a further 566 fluid ounces of acid (70.8 cups or about 4-1/2 gallons) to get the TA lowered to 100, but it will take quite a few cycles of aeration and acid addition to do so. It will go fastest if you add acid every time the pH rises to 7.2. You do NOT just add acid every so often -- you don't want to go below 7.0. You would add around 59 fluid ounces (7.4 cups or about 1/2 gallon) when the TA is high and around 32 fluid ounces (4 cups) when the TA gets closer to 100. As for how many cycles, this depends on how high you let the pH go. It's a tradeoff between making the whole process go more quickly but adding acid more frequently vs. letting the pH go higher which makes the process go more slowly but you don't add acid as often (but add more acid each time since there's a larger pH more to make).

Regardless of how you do this -- whether quick or slower or even not at all and just adding acid every week over a year -- it's the same total amount of acid to lower the TA from 250 to 100 in 19,000 gallons of 728 fluid ounces (91 cups or 5.7 gallons). Of course, if you've got lots of evaporation and your fill water is high in TA, then that will tend to increase TA over time and will be counter to your TA lowering efforts, but there's not much you can do about that (unfortunately) except getting a pool cover to reduce evaporation.

Richard
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Postby justjabbin » Wed 29 Aug, 2007 21:13

I have a test kit from Taylor and a smaller drop test kit from Pentair that came with my brush. I like the Pentair because it has PH down to 6.8 and Taylor only down to 7.0. However Pentair has no distication from the 6.8 to 7.2 range so using both helps me really dial it in. The pentair TA test seems a little inconsistent but my first taylor TA this morning was 270. this evening was 230. I started at Ph 7.8...lowered it to 7.0 with approx 2 gallons of acid then aerated for a few hours and was at 7.2 So I added more acid (1/2 gal) and am now back to 7.0 I am aerating again right now. I am assuming that as my TA comes down it will take less acid to lower PH or will it take more?
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Postby fatybabe » Wed 29 Aug, 2007 21:59

As stated already by Richard both kits should give the same results, might i suggest you use Palintest i tend to find them being the most reliable.

In addition there are some cheap photometers availble in the market that might give you a better reading, check out Lamotte for those.

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