really HIGH alkalinity for a long time....

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
johanss
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really HIGH alkalinity for a long time....

Postby johanss » Thu 23 Aug, 2007 14:16

My alkalinity is 230 and has been for amost 2 months...my pool store
has told me to add dry acid 10lbs for my vol.12,600 gal. It has not
changed at all. At first the ph was great all the time now the ph is a little
lower 7.4 What do I do? No one here at the two pool stores have a clue.


chem geek
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Postby chem geek » Thu 23 Aug, 2007 15:01

First of all, a high TA is not a problem unless you are experiencing a strong tendency for the pH to rise over time or have a plaster/gunite/tile pool or have hard water, that is high Calcium Hardness (CH), in which case you could get cloudiness and scaling.

I suspect you are using an acidic source of chlorine, probably Trichlor tabs/pucks, or else you would be seeing the pH go up more rapidly. In fact, it's possible that you were using Trichlor and the pH was low so you added pH Up which over time increased your TA level because pH Up adds carbonates to the pool just like Alkalinity Up -- it doesn't just raise the pH. By the way, a pH of 7.4 is fine.

If you want to lower the TA, the way to do that is by following the procedure in this post. Only a combination of low pH with aeration will lower the TA efficiently. Adding acid alone will not do it, though the process at low pH and with aeration does require adding lots of acid.

I suspect you will be having issues with algae soon unless you use an algaecide or are keeping your Free Chlorine (FC) levels relatively high. With the constant use of Trichlor, your Cyanuric Acid (CYA) levels may keep building up unless you have a lot of dilution from backwashing or splash-out.

If you post a full set of pool water chemistry numbers, we can see where you are at. Free Chlorine (FC), Combined Chlorine (CC), pH, Total Alkalinity (TA), Cyanuric Acid (CYA), Calcium Hardness (CH). Also give us your pool water volume and the type of pool (in-ground, above-ground; plaster/gunite/tile vs. vinyl) and location (outdoors; amount of sunlight; indoors). If you do not already have one, please get yourself a proper test kit, the Taylor K-2006 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 .

Richard
johansst

high alkalinity reply to chem geek

Postby johansst » Sat 25 Aug, 2007 10:29

Hello, I am not sure if this is how to reply...To Chem geek....
My pool is fiberglass and the vol.is 12,600 gal. fac-1.0 tac-1.0
PH-7.4 TA-230 calcium hardness is 320 cyanuric acid is 30
tds - 2200 and copper/iron-0 The leslie store here told us
to add 10lbs of dry acid at 1lb at at time every 4 hours...can I use
liq.mera.acid? And do you think that this will help? Oh you asked
if we used chlorine pucks, yes we just started using the large ones
from costco about 3 weeks ago...before were leslie small tabs. I do
not know enough to tell if they are trichlor without looking on the box.

we do not do backwashing in our system...we got our pool from MID-
WEST fiberglass and it uses filters large long ones. we change about
ever two weeks and wash and soak them in hot water with dawn dish
wash liq. Do you think that is our problem...Thanks for the info on the
last reply. johansst
chem geek
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Postby chem geek » Sat 25 Aug, 2007 16:58

Since your Calcium Hardness is high and your CYA is reasonable (i.e. low), I'm guessing that you previously used Cal-Hypo as your source of chlorine. The large pucks you now have from Costco might be Trichlor -- you should look at the package to see what they are. You can use the Trichlor, if that's what it is, for a while since your CYA isn't high, but you'll have to maintain higher Free Chlorine levels than you've been doing or else use a weekly maintenance dose of PolyQuat 60 algaecide. So add some more chlorine to your pool right away to get to 3 ppm FC.

As for your calcium carbonate saturation level (aka Calcite or Langelier Saturation Index), it's about +0.2 which isn't bad -- a little higher than ideal, but not bad. You can lower your TA to 100 ppm and have a target pH of 7.5 and you should be in good shape. To lower your TA, you follow the procedure described in this post and yes, you should use Muriatic Acid instead of Dry Acid. Dry Acid is Sodium Bisulfate and adds sulfates to the water. That's not terrible, but over time if that's the only type of acid you use then you can build up sulfates which may cause some issues for certain pool surfaces (we don't have a lot of data on that yet, but I'm more inclined to use Muriatic Acid instead).

Your TDS is on the high side for a non-salt pool. It's not a problem, but probably indicates little water dilution -- since you don't backwash. Usually, the TDS only builds up to that level if you use bleach or chlorinating liquid since Cal-Hypo has less salt in it, but again, it's not a problem (I'm just thinking out loud, so to speak).

I calculate that it will take 68 fluid ounces of Muriatic Acid (31.45% strength) to lower the pH to 7.0 at which point you want to aerate the pool as much as you can -- turn the eyeballs up in the returns, run any waterfalls, spillovers, showers or other water features you may have, use an air compressor/pump to blow bubbles into the deep end, etc. The more you aerate, the faster the TA lowering process will occur. The aeration will cause the pH to rise. When it gets to 7.2, then add 37 fluid ounces to lower the pH back to 7.0, then aerate some more, etc. The sequence of events will be something like the following:

68 ounces acid; pH 7.4 --> 7.0 ; TA 230 --> 208.9
Aerate; pH 7.0 --> 7.2 ; no change in TA
37 ounces acid; pH 7.2 --> 7.0 ; TA 209 --> 197.4
Aerate; pH 7.0 --> 7.2 ; no change in TA
35 ounces acid; pH 7.2 --> 7.0; TA 197.4 --> 186.4
Aerate; pH 7.0 --> 7.2 ; no change in TA
33 ounces acid; pH 7.2 --> 7.0 ; TA 186.4 --> 176.1
Aerate; pH 7.0 --> 7.2 ; no change in TA
32 ounces acid; pH 7.2 --> 7.0 ; TA 176.1 --> 166.4
Aerate; pH 7.0 --> 7.2 ; no change in TA
30 ounces acid; pH 7.2 --> 7.0 ; TA 166.4 --> 157.0
Aerate; pH 7.0 --> 7.2 ; no change in TA
28 ounces acid; pH 7.2 --> 7.0 ; TA 157.0 --> 148.1
Aerate; pH 7.0 --> 7.2 ; no change in TA
27 ounces acid; pH 7.2 --> 7.0 ; TA 148.1 --> 139.7
Aerate; pH 7.0 --> 7.2 ; no change in TA
26 onces acid; pH 7.2 --> 7.0 ; TA 139.7 --> 131.7
Aerate; pH 7.0 --> 7.2 ; no change in TA
24 ounces acid; pH 7.2 --> 7.0 ; TA 131.7 --> 124.1
Aerate; pH 7.0 --> 7.2 ; no change in TA
23 ounces acid; pH 7.2 --> 7.0 ; TA 124.1 --> 117.0
Aerate; pH 7.0 --> 7.2 ; no change in TA
22 ounces acid; pH 7.2 --> 7.0 ; TA 117.0 --> 110.1
Aerate; pH 7.0 --> 7.2 ; no change in TA
21 ounces acid; pH 7.2 --> 7.0 ; TA 110.1 --> 103.7
Aerate; pH 7.0 --> 7.2 ; no change in TA
20 ounces acid; pH 7.2 --> 7.0 ; TA 103.7 --> 97.4
Aerate a lot; pH 7.0 --> 7.5 ; no change in TA

As you can see the process takes a lot of acid and is time consuming. You can, of course, aerate to have the pH go up to more than 7.2 at each step and then need to add more acid to get the pH lower, but this will take a longer period of time since the pH rise from aeration is fastest when the pH is lower. To get from your pH 7.4 TA 230 to a pH 7.5 TA 100 will take a total of 419 fluid ounces (26.2 gallons) of Muriatic Acid no matter how you try and lower the TA. That's why I asked if the high TA was a problem for you. You can also just lower it some and not all the way.

Though you can certainly lower the TA as described above, if you use Trichlor pucks/tabs, then this will be acidic and tend to lower the pH anyway. Whatever you do, do NOT use pH Up to raise the pH -- this will just increase TA a lot as it adds carbonates to the water (pH Up is Sodium Carbonate and raises both pH AND TA). Instead, try and use aeration to raise the pH since that doesn't raise the TA at all. If this is not sufficient, then use 20 Mule Team Borax to raise pH (and it will raise the TA as well, but by half as much as pH Up) -- you use twice as much by weight as you would for pH Up.

Do you have any idea how your TA got so high in the first place? Test your fill water for TA and CH to see if they are high, but unless you've got a lot of evaporation, you shouldn't be adding much fill water to your pool. Something just seems fishy about your situation. If you had been using Trichlor before, then using pH Up to maintain pH could have led to the high TA, but then you should have high CYA as well.

By the way, if you just added 10 pounds of dry acid to your pool, then that would lower the pH to 6.8 and the TA to 193.1 and you'd have to aerate or just wait (since outgassing happens even when you don't aerate -- the aeration just speeds it up) until the pH went up with no change in TA. So though they were on the right track, they were nowhere near where you needed to be. Adding 1 pound would lower the pH from 7.4 to 7.3 but it takes more acid to lower the pH as it gets lower. 10 pounds of dry acid is equivalent to 119 fluid ounces of Muriatic Acid (31.45% strength).

And before you do anything else, don't forget to get yourself a good test kit as I described in my earlier post.

Richard
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Postby fatybabe » Tue 28 Aug, 2007 05:35

Richard advice you provided is good, but you will be scaring ppl away what they need is something simple.


My word of advice:

1.Back wash your filter.
2.Bleed off 1/2 the amount of water in your pool
3. Add in fresh water and check the TA.

TA should be in better balance by now or should be alot easier for balance.
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Postby Backglass » Tue 28 Aug, 2007 12:17

fatybabe wrote:Richard advice you provided is good, but you will be scaring ppl away what they need is something simple.


My word of advice:

1.Back wash your filter.
2.Bleed off 1/2 the amount of water in your pool
3. Add in fresh water and check the TA.

TA should be in better balance by now or should be alot easier for balance.


But what if the supply water has a high TA as well? Your method would have no effect. It is silly to drain half your pool to correct high TA...not to mention expensive.
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Postby chem geek » Tue 28 Aug, 2007 18:58

You're both right. If the TA of the fill water is lower, then a partial drain/refill will lower the TA. If the TA of the fill water is high, then only aeration with acid addition will lower it -- though it is not necessary to do it all at once. The pool will slowly over time lose TA, but will also need regular acid addition (i.e. the pool outgasses even without explicit additional aeration).

I appreciate the alternative suggestion. It's a good one when applicable and in this case we don't know the TA of the fill water so it certainly was reasonable to suggest.
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Postby mr_clean » Tue 28 Aug, 2007 21:12

just a note,
there is a new product out called "easy acid" made by United Chemicals it comes in one pound bags $1.39 or bucket and is made to lower Alkalinity. I used this in a pool with alkalinity at 180 and put in the amount suggested 1 bag per 10,000, so I added 3 bags 25,000 with PH at 7.8
I did this twice over 2 weeks and alkalinity is at 90 - PH 7.5

not trying to sell it, just letting you know

I looked for ingredients and it's protected
chem geek
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really HIGH alkalinity for a long time

Postby chem geek » Tue 28 Aug, 2007 22:39

The MSDS for this product is here and its just dry acid -- sodium bisulfate. No miracle here. Adding acid and then letting the pool automatically aerate will lower the TA, but usually you need to help it along with some aeration and it should take a lot more acid than what you added.

To get from pH 7.8, TA 180 (assumed CYA of 30) down to pH 7.5, TA 90 would take 575 fluid ounces (71.9 cups or 4.5 gallons) of Muriatic Acid or 773 ounces weight (48.3 pounds) of Dry Acid for 25,000 gallons.

I don't see how putting in only 6 pounds of dry acid got you from a TA of 180 down to a TA of 90. That amount of dry acid should lower the pH and TA to 7.3 and a TA of 169 so the pH could then go up after that to 7.5, but the TA would only drop by 10. If Trichlor was used as a source of chlorine, then less acid would be required, but not that much less. This is a mystery. Are you sure the two TA measurements were accurate?

This link talks about this acid being 300% more effective than orthodox pool acid, but I don't know why they are saying that. It is safer in that it is a solid that is less likely to get splashed.

Richard
Leigh

really HIGH alkalinity for a long time....

Postby Leigh » Mon 29 Nov, 2010 19:31

I was surfing the web for alkalinity and I found myself in this page. I recently acquired a house with a backyard pool and I know nothing in pool maintenance. My pool is a mess and my brother who works for Joe told me to check the water's pH and alkalinity. I was like what's that. He left for Canada and I know nothing about it. Thanks to this post. :)

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