TA level

IG vinyl 16X32 pool problem getting the TA down! New liner installed this year treated water using BBB. I added stabilizer and everything looks good except the total alkalinity.I use the Taylor 2006 test kit and my current numbers are:
FC= 3.5
CC = 0
PH = 7.2
TA = 175
CH = 225
CYA = 30
The TA has gone from 190 to 125 after adding 2 gal. of muratic.It went back up in two weeks to 175 .added another gal of muratic and it went done to 135.It is now back up to 175. Should I add more muratic or is something else happening?:confused:

What are you using to bring your pH back up after the acid additions?

Janet

Using Borax on two occasions one box each time .I believe there is a little over 4#'s in a box.I have been using BBB method for several years now,this is the first time I had to bring the TA down . I have a good supply of baking soda to bring it up if necessary!:)

Doesn't sound like you're gonna need the baking soda anytime soon!! :) Just wanted to make sure that you're using Borax instead of washing soda, which would bring the TA back up and defeat the purpose of the muriatic. The boxes are next to each other at my grocery store, and look similar except that they are different colors. Only thing I know to do is to add more muriatic and repeat your ratcheting process until you get it where you want it. Just make sure that you keep a close eye on your pH--you don't want it to get below 7.0 or you risk damaging your liner. Make sure you raise it up enough between acid additions so that after the addition, it's still 7.0 or higher. Is your fill water high in TA? That may be one reason why it's so high and is coming back up if you're having to refill frequently.

Sorry I don't have a more concrete answer for you, but sometimes we just have to "treat the symptoms", even when we don't understand the cause!!

Janet

In the procedure to lower the TA, you simply continue aerating without adding more acid in order to raise the pH with no change in TA. Even adding Borax will raise both the pH and the TA. It is true that it will raise the TA by half as much as soda ash, but it will still raise it; aeration won't.

I dunno...a T/A of 175 with a CH of 225 in a vinyl pool just isn't anything to worry about. It probably will have no effect at all.

Don't sweat it, don't mess up your other chemistry unless you are having troubles maintaining your desired pH.

Only then should you worry about lowering your T/A.

Vinyl pools with low CH levels are VERY tolerant of T/A levels well above the "maximum" of 125ppm. When it gets over 200ppm, then you need to act.

Only when the T/A approaches 200ppm and the CH is past 400ppm, approaching 500ppm do you have a shot of scaling and cloudy water. But you shouldn't at these levels.

Thanks for the replys,not sure I understand the reply about areation.My concern for the water chemistry stems from the problems from last year before the new liner.At what point will the low PH and or alkalinity cause metal to disolve?This problem may belong on a different thread but it pertains to chemistry of the water.
I had a staining problem that was caused by copper which was 1.0.It was thought it was coming from the heat exchanger. I installed bypass valves on the heater and planned only to use it at start up.Used it this year for two days to warm the water and put it back on bypass. Checked the water in the pool for copper and found a trace ,less than0.1 .This was not there prior to running the heater. After I bypassed the heater I thought about getting a sample of the water and drained it. The sample showed a 1.0 concentration of copper from the exchanger.Can my water be that corrosive or can the age of the heater be at fault? (10 years ,only used to start up and early fall).

OK,

What is Total Alkalinity?
Total Alkalinity is actually a bit of misnomer for anyone who remembers anything at all about high school chemistry. We think of Acidic as low pH and Alkaline as high pH. Total Alkalinity doesn't refer to that--as I said it's a bit of a misnomer.

Richard (Chem_Geek) can give you a far more precise definition, but in short T/A is a measure of the BUFFERING of pH.

That means it helps keep your pH stable, so it isn't constantly changing. The accepted normal range is 80 to 125ppm. For concrete/plaster/tile pools it's very important to keep your T/A in this range. For vinyl pools you usually won't have a problem unless you hit 200ppm AND you have a high hardness level (you don't). So it's not a big worry for us vinyl boys and girls.

Richard has challenged some of our assumptions that higher T/A in the range is better and has shown that the 80-90 range can give better buffering. That's all very technical.

But, unless you are having a problem with oscillating high and low pH levels at your T/A of 175, you simply don't have a problem with your T/A.

Where is pH dangerous to a vinyl pool?
Normally we worry about pH reading below 6.9 for vinyl pools. For concrete/plaster/tile pools, much lower pH levels can be safely tolerated without damage to the surface (I'm not expert on those).

The problem is a lot of test kits either have 6.9 or 6.8 (usually 6.8) as their lowest measured level and they don't have a fine enough differentiation for you to see if it's 6.9, 6.8 or even a little below. That's why we worry if it shows anything below 7.0--because at 7.0 we know we are in the safe range.

Low pH will soften and weaken the vinyl. Extremely low pH (like using the hideous "slug method" to lower T/A) can actually dissolve the vinyl--new wrinkling at the point where the muriatic acid was added is a warning sign.

Aeration to Lower T/A
Again, a misnomer. The process as originally described by Ben was very confusing but it's actually quite simple.

1) T/A measured levels go up and down as pH goes up and down--it's not actually that the T/A is changing, though we want to do that. If you add acid to lower T/A then add Borax to raise the pH back it will seem that you are not getting anywhere.:mad:

2) So we have to be able to raise pH and NOT have the T/A rise with it. Aeration does that. Again, without getting into the chemistry, the aeration allows certain components in the water to create a less acid and more basic solution.

3) The process is:
a) Lower pH to 7.0 by adding acid
b) aerate to raise pH back to 7.4-7.6
c) Measure T/A.
d) If T/A is not at the desired level, repeat a), b) and c) until it is...this is the "rachet" method.

4) Aeration can be splashing 12 year old boys, a fountain, or just leaving the pool uncovered and pointing the return toward the surface so the water is agitated.

That's it. I hope I helped.

Yes that helps clear up the TA ,PH issue for me.Thank you.Where can I find
Ben's detailed explanation on the maintaining higher TA?Thanks much for your help. Would rather have 20 year old girls splashing around,guess I'll have to seatle for pointing the eyeball up to the surface.

Where can I get an answer on using my pool heater or not? If my water is balanced OK why is the copper coming out of the heater ?

I would speculate that the copper is coming out of the heater due to age, and possibly due to corrosive water chemistry at some point in the past. It also may have to do with what type of heater it is--I don't know much about them but there has been some discussion in the past about the newer models being much less prone to exchanger corrosion than the older models. At least you know where the copper is coming from and caught it before it became a problem. You could always use a metal-out product to keep the copper from staining....see mbar's sticky at the top of the "metal matters" thread.

Janet

Quote:

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Originally Posted by CarlD

Richard (Chem_Geek) can give you a far more precise definition, but in short T/A is a measure of the BUFFERING of pH.

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I think your definition is just fine. Total Alkalinity (TA) has TWO effects: one is pH buffering, but the other is as a source of rising pH itself (due to carbon dioxide outgassing). So ironically, a lower TA can result in greater pH stability when using hypochlorite sources of chlorine (e.g. chlorinating liquid, bleach, Cal-Hypo, lithium hypochlorite).

The easiest rule to follow is to simply adjust the TA until the pH tends to be stable. If your pH tends to rise over time, you can lower the TA (within reason) to reduce the rate of rise. If your pH tends to fall over time, you can raise the TA to reduce this rate of rise.

After you've settled on a reasonable TA that has the pH be relatively stable, then you can adjust the Calcium Hardness (CH), if needed, to have the saturation index be near zero to protect plaster surfaces. As noted by Carl, this index isn't as important in a vinyl pool so you normally don't worry about the CH (unless it's high since that can lead to scaling).

Richard