TA level

[CarlD]

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.

[essikr]

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).

[CarlD]

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.

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.

[essikr]

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 ?

[aylad]

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

[chem geek]

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

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