Adjusting PH and TA

[ny poolguy]

Topic split off by Moderator from this thread

I've always found when PH and TA are low,getting the TA up to around 80ppm will usually bring your PH within range. If you get your PH in range first when you raise TA it will raise PH even more.

 

[Butterfly]

Re: Converting swamp to pool (pics included)

I've always found when PH and TA are low,getting the TA up to around 80ppm will usually bring your PH within range. If you get your PH in range first when you raise TA it will raise PH even more.

Baking soda will be used to raise the TA which has little effect on the pH.

 

[ny poolguy]

Re: Converting swamp to pool (pics included)

I've always found when PH and TA are low,getting the TA up to around 80ppm will usually bring your PH within range. If you get your PH in range first when you raise TA it will raise PH even more.

Baking soda will be used to raise the TA which has little effect on the pH.

I'm just going by the many pools I've cleaned and maintained through the years. Pools that the TA is at 0ppm and the PH is off the chart low,bringing the TA up to around 80 or 90ppm almost always brings PH into range.

 

[chem geek]

Re: Converting swamp to pool (pics included)

When the pH and TA are both very low, then adding baking soda does bring the pH up a lot, but when the TA isn't so low, then baking soda raises the TA much more than it raises the pH. For example, if one uses Trichlor and doesn't adjust pH or TA, then getting the pH down to 4.0 and the TA below 0 (it measures as 0), adding baking soda to get the TA to 100 ppm gets the pH to around 6.2, not counting some outgassing of carbon dioxide that can occur from the baking soda addition (so the pH could rise higher than 6.2). On the other hand, with your starting numbers of pH 6.5, TA 50, CYA 0, adding enough baking soda to get the TA to 80 would only raise the pH to around 6.8; again, unless the addition is done quickly in one place where carbon dioxide outgassing could have the pH raise somewhat more.

 

[frustratedpoolmom]

Re: Converting swamp to pool (pics included)

I'm just going by the many pools I've cleaned and maintained through the years. Pools that the TA is at 0ppm and the PH is off the chart low,bringing the TA up to around 80 or 90ppm almost always brings PH into range.

In the case that began this discussion the TA was 50. Its my understanding that is not so low that it would cause large changes in PH. And Richard confirms my assumption (I think... ?):

On the other hand, with your starting numbers of pH 6.5, TA 50, CYA 0, adding enough baking soda to get the TA to 80 would only raise the pH to around 6.8; again, unless the addition is done quickly in one place where carbon dioxide outgassing could have the pH raise somewhat more.

 

[ny poolguy]

Re: Converting swamp to pool (pics included)

When the pH and TA are both very low, then adding baking soda does bring the pH up a lot, but when the TA isn't so low, then baking soda raises the TA much more than it raises the pH. For example, if one uses Trichlor and doesn't adjust pH or TA, then getting the pH down to 4.0 and the TA below 0 (it measures as 0), adding baking soda to get the TA to 100 ppm gets the pH to around 6.2, not counting some outgassing of carbon dioxide that can occur from the baking soda addition (so the pH could rise higher than 6.2). On the other hand, with your starting numbers of pH 6.5, TA 50, CYA 0, adding enough baking soda to get the TA to 80 would only raise the pH to around 6.8; again, unless the addition is done quickly in one place where carbon dioxide outgassing could have the pH raise somewhat more.

Chem geek,Butterfly,and frustratedpoolmom, I agree with you that raising TA with baking soda will not have is much effect on pH. Chem geek,this is what's been puzzling me....why do my experiences with pH and TA seem to defy science? They can't. So here's my theory after a little research. We know TA is a buffer for pH. I've heard pH described as a see-saw and TA leveling it out. I would take that meaning neutral pH or 7.0. Also,that if TA is too high it will cause high pH(I assume it's because baking soda has a pH of 8.4). If that's the case then that says to me there's some point past 80ppm of TA that pH will start going past neutral using only baking soda. Any thoughts?

frustratedpoolmom,I'm not sure if this has turned into a deep end... topic?

 

[JasonLion]

ny poolguy, because baking soda has a PH of about 8.4, it tends to push the PH towards 8.4 when added. Compared to other things you might use to raise PH, baking soda is a very weak base, so the PH shift is only significant when the TA level starts quite low and the PH starts very far from 8.4.

TA has two independent effects. It increases the amount of a chemical that needs to be added to get a given change in the PH, kind of like adding friction on the see-saw axel. And, it tends to put "pressure" on the PH to move towards 8.4, kind of like a rubber band trying to pull the see-saw towards the 8.4 position. The more the rubber band gets stretched, ie the further the PH is from 8.4, the more pressure there is on the PH. The higher the TA level, the more friction on the axel and the stronger the rubber band gets. Also, the rubber band gets stronger faster than friction is added to the axel, so the PH is more likely to move the higher the TA level is. To finish off the analogy (which is getting a little stretched at this point) aeration is like some special lubricant, that lowers the friction on the axel from the point of view of the rubber band, without lowering it from the point of view of adding chemicals. (I think the analogy just snapped )

 

[ny poolguy]

ny poolguy, because baking soda has a PH of about 8.4, it tends to push the PH towards 8.4 when added. Compared to other things you might use to raise PH, baking soda is a very weak base, so the PH shift is only significant when the TA level starts quite low and the PH starts very far from 8.4.

TA has two independent effects. It increases the amount of a chemical that needs to be added to get a given change in the PH, kind of like adding friction on the see-saw axel. And, it tends to put "pressure" on the PH to move towards 8.4, kind of like a rubber band trying to pull the see-saw towards the 8.4 position. The more the rubber band gets stretched, ie the further the PH is from 8.4, the more pressure there is on the PH. The higher the TA level, the more friction on the axel and the stronger the rubber band gets. Also, the rubber band gets stronger faster than friction is added to the axel, so the PH is more likely to move the higher the TA level is. To finish off the analogy (which is getting a little stretched at this point) aeration is like some special lubricant, that lowers the friction on the axel from the point of view of the rubber band, without lowering it from the point of view of adding chemicals. (I think the analogy just snapped )

Jason,it took while to "stretch" my mind around that analogy Although it answered some questions about baking soda's effects on TA and pH,it opened the door to many others. Like chlorine and non-chlorine products effect on pH(because of oxidation),but that's more suited for it's own topic.

So if there are two pools
Pool A - with 100ppm of TA and 7.0pH
Pool B - with 50ppm of TA and 7.0pH
Pool A is harder to move pH than pool B,but if pool B is raised to 100ppm of TA the carbonic quality of baking soda and the forces of TA are not enough to raise pH above 7.2 ?
I think I got it :?

 

[JasonLion]

If you add one quart of muriatic acid (for example) to both pools, pool A will have about half the PH shift that pool B will have.

If you raise the TA level in pool B to 100, the PH will change to about 7.17. On the other hand if pool B started at a TA level of 10, raising TA to 100 would raise PH to 7.67, almost 4 times the PH change for less than double the TA change.

If you aerate both pools, pool A will see the PH increase far more quickly than pool B.

 

[frustratedpoolmom]

Off to Chemistry 201, but keep it up and you'll be in the Deep End.