Trying to Understand this TA/pH Marriage

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
Guest

Trying to Understand this TA/pH Marriage

Postby Guest » Mon 11 Jun, 2007 08:07

Is there anyway to adjust TA and pH individually?
My numbers are pretty good right now but my TA is reading 140ppm while my pH is on the low end of ideal at 7.2.
If I attempt to lower the TA then there goes my pH.

Is there a simple soultion?

(23,000 gallon vinly liner)


Guest

Re: Trying to Understand this TA/pH Marriage

Postby Guest » Mon 11 Jun, 2007 09:43

Anonymous wrote:Is there anyway to adjust TA and pH individually?
My numbers are pretty good right now but my TA is reading 140ppm while my pH is on the low end of ideal at 7.2.
If I attempt to lower the TA then there goes my pH.

Is there a simple soultion?

(23,000 gallon vinly liner)


They're rather closely linked together. A high-ish alkalinity combined with a low-ish pH will cause carbon dioxide to outgas and this in turn will raise the pH, all without doing anything. In other words if you leave things as is your pH should rise a bit and your alkalinity should drop a bit.

Do keep in mind that if you have enough cyanuric acid in the water then it too counts as "alkalinity" and your TA number should be tweaked to reflect the presence of CYA.

Of all the pool parameters the pH is probably the one that's easiest to adjust both upwards and downwards so I wouldn't worry too much about it.

A 'high' alkalinity is usually lowered by dropping the pH to around 7.0 and _maintaining_ it there (requiring a constant addition of pH-) and turning on the fountains or anything that disturbs the surface of the water, this to promote the elimination of CO2.

Once you're done lowering the TA you can always put the pH back where you want it.
Guest

Re: Trying to Understand this TA/pH Marriage

Postby Guest » Mon 11 Jun, 2007 11:55

[quote= A high-ish alkalinity combined with a low-ish pH will cause carbon dioxide to outgas[/quote]
Is this the reason that I've noticed mored "foaming" on the surface lately when the kids swim?

[quote= Do keep in mind that if you have enough cyanuric acid in the water then it too counts as "alkalinity" and your TA number should be tweaked to reflect the presence of CYA. /quote]
Cyanuric acid levels are currently around 25-30ppm

[quote= Once you're done lowering the TA you can always put the pH back where you want it.[/quote]
So, is it safe to say that if I had to prioritize between the two, that I should first be concerned with TA, then pH?

Thanks for your input!
Joe
Guest

Re: Trying to Understand this TA/pH Marriage

Postby Guest » Mon 11 Jun, 2007 15:14

I think the foaming may be caused by oil or lotions (saponification maybe?), but I'm no expert in foaming.

At 25-30 ppm then the CYA effect on total alkalinity is negligeable, and is well within the error range of the TA test (+- 10 ppm).

Certainly I would try to adjust the alkalinity and get it in the proper range. Depending on the type of chlorine you use you may want a lower TA (for cal hypo, lithium, bleach, swg) or a bit higher in the case of dichlor and trichlor. Then readjust the pH where you want it.

You may also wish to consider adding borax to the pool water. 50 ppm borax is a proven algeastat and it really locks in the pH. These effects can be explained chemically (I won't go into any of that here!) What I cannot explain however is the added sparkle to the water and a 'softer feeling' water. Borax is available under many trade names at the pool store, Bioguard Optimizer, ProTeam Supreme, or at Walmart (if you have such stores) as 20 Mule Team. You'll have to compensate the rising pH when using 20 Mule Team so have some (a lot of) pH-. But it's well worth the effort.

But anyways, yes, certainly TA is a tad "difficult" to lower and if it's set too high wil cause your pH to drift upwards. I would tackle the TA first, yes.
Guest

Postby Guest » Mon 11 Jun, 2007 15:23

You've been very helpful. Thanks!

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