High total alkalinity and low PH

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

High total alkalinity and low PH

Postby gglmn » Tue 17 Jul, 2007 11:38

I have High total alkalinity and low PH. Total alkalinty is 218, PH is 6.8, and I'm constantly adding PH UP. Can't seem to get it under control. I do have BioGuard® Optimiser so my local pool store says the high total alkalinty is OK.


Backglass
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Re: High total alkalinity and low PH

Postby Backglass » Tue 17 Jul, 2007 12:32

gglmn wrote:I have High total alkalinity and low PH. Total alkalinty is 218, PH is 6.8, and I'm constantly adding PH UP. Can't seem to get it under control. I do have BioGuard® Optimiser so my local pool store says the high total alkalinty is OK.


PH-UP (which is just baking soda at 10x the price) will also raise your TA which is already too high. Borax (20 Mule Team from the laundry aisle) will raise your ph and leave your TA alone.

The easiest way to raise your ph however (and chemical free) is aeration. A fountain, waterfall, air hose, or even pointing your returns up so the water ripples will all raise ph.
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Postby chem geek » Tue 17 Jul, 2007 13:58

BioGuard Optimizer is almost identical to Borax (it has less water in it as a hydrated crystal than Borax). This is an additional pH buffer, but it sounds like Trichlor tabs are being used heavily since they are very acidic. I suspect that CYA levels are very high which is requiring a lot more Trichlor to be used to add enough chlorine to prevent algae.

Normally, a high TA will cause the outgassing of carbon dioxide to raise the pH to compensate for the Trichlor acidity, but you must not have much aeration in your pool. By any chance are you using a pool cover? If so, then that keeps the carbon dioxide in the pool. You should get a good test kit, the Taylor K-2006 or the TF-100 at tftestkits(dot)com and test your CYA level (among other tests). If it's really high, then you should consider a partial drain/refill to lower it and switching to an unstabilized source of chlorine such as bleach or chlorinating liquid (or Cal-Hypo if your calcium level is low).

Richard
gglmn

Postby gglmn » Thu 26 Jul, 2007 22:01

Thanks for the info. Richard you hit the nail on the head. I looked at my tabs and they are Stabilized Trichlor tabs. We go through about 4 to 6 3" pucks a week. We also have an autocover so the pool is usually covered. I'll get the water tested and see what the results are.
chem geek
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Postby chem geek » Fri 27 Jul, 2007 02:07

Well you are in a great situation for using unscented bleach or chlorinating liquid as your source of chlorine. I also have an opaque automatic safety cover and by keeping sunlight out most of the time, the chlorine usage isn't more than 1 ppm FC and that's using the pool every day -- if using it less frequently, the usage can be only 0.5 ppm FC per day.

So that means that if you get your CYA lower, to around 30 ppm or so (at least down to 50 ppm), then you should be able to add chlorine just twice a week to the pool, which is what I do. That's much easier than having to do it every day which many without a cover and with a pool in direct sunlight have to do.

Richard

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