Just Ow Much Ph- Do You Need!

[macgd016]

I keep my pool pH at 7.4, it needs about 200gr pH- for every 1000 litres fill up to achieve this. The pool is beautifully clear and I have no problems at all, however, the TA is above 240 so I thought about dropping the pH and aggregating the water to drop the TA. The pool is only 50,000 litres and I have put in around 8kg pH- with little or no effect. 750gr are supposed to drop the pH by 0.2 so I am at a loss to understand what is going on. Any thoughts?

[macgd016]

Oops looks like I can answer my own question! Whilst the pH has stayed between 7.2 & 7.4 the TA has dropped like a stone to about 70. I must admit I had assumed the change would be more gradual, I thought the pH would drop quickly and then rise as the TA reduced but it al seems to have happened very quickly. Oh well the TA is a bit low but I guess it will come back up in time.

[chem geek]

Adding acid will lower both the pH and the TA, but the pH may rise back up from outgassing of carbon dioxide. Usually you do a combination of adding acid and aerating the water to lower the [EDIT] TA [END-EDIT].

8 kilograms of Dry Acid (93.2% sodium bisulfate) in your 50,000 liter pool would lower the TA by 62 ppm to 178 ppm. The pH would drop to 6.6, but outgassing of carbon dioxide could have it stay above 7.2 or higher. I suspect one or both of your TA readings is wrong. If you are using test strips, they are worthless and you need to get yourself a good drop-based test kit such as the Taylor K-2006.

[macgd016]

Adding acid will lower both the pH and the TA, but the pH may rise back up from outgassing of carbon dioxide. Usually you do a combination of adding acid and aerating the water to lower the pH.

8 kilograms of Dry Acid (93.2% sodium bisulfate) in your 50,000 liter pool would lower the TA by 62 ppm to 178 ppm. The pH would drop to 6.6, but outgassing of carbon dioxide could have it stay above 7.2 or higher. I suspect one or both of your TA readings is wrong. If you are using test strips, they are worthless and you need to get yourself a good drop-based test kit such as the Taylor K-2006.

The Taylor kits are not available in Europe but I have been using a tablet based test. The readings were correct and even stranger now is that after adding 1000 litres of fresh water the TA is back above 200 and the pH is somewhere around 8. All very strange, I think I will let it all settle down for a little while and see what happens.

[chem geek]

In Europe, see if you can get the Palintest Pooltester SP 315C. This has everything you need except a FAS-DPD chlorine test. The Palintest SP 300 is a separate FAS-DPD chlorine test, but may only be available in the U.S. (but you can ask about it because maybe now it is available in Europe).

[waterbear]

[ The readings were correct and even stranger now is that after adding 1000 litres of fresh water the TA is back above 200 and the pH is somewhere around 8. All very strange,

Not strange at all. Test your fill water. What is the TA? I bet it is high.

[macgd016]

In Europe, see if you can get the Palintest Pooltester SP 315C. This has everything you need except a FAS-DPD chlorine test. The Palintest SP 300 is a separate FAS-DPD chlorine test, but may only be available in the U.S. (but you can ask about it because maybe now it is available in Europe).

I did look into getting a Palintest kit as you have recommended them before but I was unable to find a retail outlet that sold them and Palintest were not very helpfull. Instead I have a similar tablet based kit that tests FC, pH and Ta and will probably add CYA and others as I need them.

[Poolcuzy]

This problem seems similar to mine. Some info first:

This is a small pool, or a largish jacuzzi-2500 gallons (about 9.5 cubic meters).

It is half in ground half out ground

It is lined with marmolite

I use 4 venturi pipes always open

The filter is DM based -24 cubic feet per hour

I live in the tropics-hot sun and some rain every day

I do not heat the water

It is not new, but I just recently decided to try manage it myself

Recent reading is:

Chlorine 5.10 (for the tropics this is good)

TA 100

cyanuric acid 45

PH- soaring out of the scale- I have to add about 30 drops in the acid demand test to get this sample to a decent color.(kit instructions only show maximum of 3 drops!)

How is this possible?

On the other hand, water looks transparent, nothing strange I can see.

How an I lower the PH so much and keep good TA? i was told to always adjust TA first, but how can PH be so high?

How should I proceed?

[waterbear]

This problem seems similar to mine. Some info first:

This is a small pool, or a largish jacuzzi-2500 gallons (about 9.5 cubic meters).

It is half in ground half out ground

It is lined with marmolite

I use 4 venturi pipes always open

The filter is DM based -24 cubic feet per hour

I live in the tropics-hot sun and some rain every day

I do not heat the water

It is not new, but I just recently decided to try manage it myself

Recent reading is:

Chlorine 5.10 (for the tropics this is good)

TA 100

cyanuric acid 45

PH- soaring out of the scale- I have to add about 30 drops in the acid demand test to get this sample to a decent color.(kit instructions only show maximum of 3 drops!)

How is this possible?

On the other hand, water looks transparent, nothing strange I can see.

How an I lower the PH so much and keep good TA? i was told to always adjust TA first, but how can PH be so high?

How should I proceed?

What kind of test kit are you using? Some test kits do not include a chlorine neutralizer in the pH reagent and can get a false high on pH when the chlorine is above about 3 ppm (and you are keeping yours at 5 ppm)! Make sure your pH reagent includes the chlorine neutralizer. If it does not then get a different kit that does.

[Poolcuzy]

The brand is "Pool Style" it's the kind that you take a sample of water and add drops to it, then compare color with a strip attached to the sample tube. The PH test calls for 5 drops of a little bottle containing a red liquid "phenol"

The acid demand test you use the same treated sample and count drops of another bottle called "AD-40". The chart with the instructions only shows what to do for 3 drops. I'm counting 30, so I'm way off.

There's no indication to add anything before the tests in the instructions. Yet I can't help but feel the reading must be wrong.

[quantumchromodynamics]

30 drops of acid demand is not realistic with a TA of 100. You should get a different test kit.

I am not familiar with marmolite, but it seems to contain hydroxides. Perhaps the marmolite is causing some pH increase. Is the marmolite smooth or rough? Has the texture changed over time?

The venturis will create a lot of aeration, which will cause carbon dioxide to be off-gassed. Your current TA is 100 ppm, what was it the last time you tested?

What chemicals have you been adding?

[quantumchromodynamics]

The Acid Demand titrating reagent and the Total Alkalinity titrating reagent are both acids. I think that for the Taylor kit, both reagents are about the same concentration of sulfuric acid (0.12N). Therefore, it wouldn't make sense for the TA to take only 10 drops, which drops the pH to 4.5, and the pH to take 30 drops to lower the pH to 7.5, even accounting for the different sample sizes.

Possibly, if all of the TA is from hydroxides, there are no bicarbonates, the pH sample size was about 4 times larger than the TA sample size, and if the Total Alkalinity titrating reagent is stronger than the Acid Demand titrating reagent, you might get results like those that you are describing.

This might happen if you started out with near zero alkalinity and low pH and used about 28 ounces of sodium hydroxide to raise the pH.

Also, the high levels of aeration would convert much of the carbonate alkalinity into hydroxide alkalinity.

Try using the Acid Demand titrating reagent for the TA test and the Total Alkalinity titrating reagent for the acid demand test and report back the results.

Titrating reagent is the reagent you add while counting the drops until the color changes.

Also, measure the TA and pH of your fill water and report those results.

After that, add 10 ounces volume of 31.45 % muriatic acid, circulate, and retest pH and TA in 1 hour.

[Poolcuzy]

Marmolite appears to be a brand of some sort of plaster that contains some marble dust. It is basically white with a green hue.It used to be rougher. It is still rather rough. But I think the roughness accounts only for the lazyness of the guy who applied the plaster.

Today's reading shows a slight decrease of TA, at 90. PH still off scale. Chlorine a little low, so I added some, the kind that comes with calcium, not with cyanuric acid. The Cyanuric acid is up to 55. From the last reported reading all I did was add a chlorine tablet for a coupe of days. Then removed it the day before yesterday. Nothing added yesterday and I'm giving you today's late afternoon reading. This thing is so small I cannot keep a tablet going for too long or the cyanuric acid rises wild. I also added a tad of "TA Up" to aim he TA towards 100 again, but that was after the reading. Maybe I should mention I keep my filters on a timer for about three hours/day between 3 PM and 6 PM. I take the readings and add chemicals when they are on.

I will try the suggestions tomorrow. I'm reading the message too late today. Will report.

[quantumchromodynamics]

If your pH is too high, the last thing you want to add is TA up. What is the actual ingredient listed on the container of TA up?

Reducing the aeration from the venturis would help a lot in preventing pH rise. There should be a way to close the air inlet to the venturis.

Marmolite is a type of serpentine Mg₃Si₂O₅ (OH) ₄, which appears to be some type of mineral, like marble. I'm thinking that the hydroxides might be contributing to the pH increase if the material is dissolving.

Is this spa plastered or is it made out of sheets of marmolite?

Can you provide a calcium reading?

[Poolcuzy]

This is after heavy rain and the little pool actually overflowed.

The Alkalinity is down to 80. The PH still high.

I did the experiment of using the Alkalinity titrating reagent with the PH sample. Just one drop and it falls down to 6.8. Using the PH titrating reagent with the alkalinity test I stopped counting fearing the bottle would empty with no change in color. Does that means my AD-40 is expired or something?

The TA up ingredient is sodium hydrogen carbonate.

The spa is plastered.

I don't have a calcium test in my kit.

I will get some muriatic acid. But my fear is that if the test is right (which I doubt) then it will screw up the TA.

I rather think there is something wrong with the AD-40. I'm tempted to go to the pool store and get a new AD-40 bottle instead of the acid?

[quantumchromodynamics]

Sodium hydrogen carbonate is regular Arm and Hammer baking soda. The pool store just uses the technical name so that they can charge you twice as much.

Since the spa is plastered, and it is referred to as "marmolite", I am going to guess that the plaster is a mix of white cement and marmolite is the aggregate. You should maintain a neutral to positive CSI (Calcite Saturation Index) to protect the plaster. You can calculate your CSI with the poolcalculator. Be sure to enter all of the variables.

What are all of you readings?

pH

TA

Calcium

Cyanuric acid

Borate

Temperature

I wouldn't trust the acid demand titrating reagent. It shouldn't go bad, but it does not seem accurate. Get a new bottle of pH indicator. If the pH is still measuring high, add about 2 ounces volume of 31.45 % muriatic acid, circulate, and retest pH and TA in 1 hour. Keep doing that in small increments until the pH is down to about 7.8.

Don't worry about the TA going too low. You should allow the TA to go wherever it needs to to keep the pH stable at 7.8.

I recommend a pH of 7.7 to 7.9. Using a higher pH range will allow you to maintain a higher TA. Once you get your pH and TA in the range you are happy with, you should increase your calcium hardness to achieve at least a 0.0 CSI.

The filter is DM based

What is DM? Do you mean DE?