Perfect storm for CH scaling

[Hemess]

Same thing that causes calcium scale in a new pool, or any pool for that matter. Calcium scale is usually the result of a "perfect storm" type of water chemistry. If you have high calcium levels, say 400 ppm or better and pH above 7.5 and TA over 120 you are at risk of developing calcium scale. High calcium levels can be managed if you keep the pH and TA on the low end of the acceptable range, say 7.2 and 70ppm respectively.

Bottom line is when the pool is properly balanced there will be no scale formation.

I have the perfect storm in which you are referring to. So sad. I thought my plaster was lightening, but I just realized tonight that it has a coating on it.

Used Leslie's Test Kit 81-330...then raced to get some chemicals, and they tested my water too. Results were similar, but I think mine are more accurate because the guy running the chemicals was sloppy and I was precise! But here they are:

FAC 3 (store said 5)
TAC 3 (store said 5)
CC 0
PH needed 7 drops, so I am adding 1.5 gallons over the next two days. (Store added 5 drops)
TA 190 (Leslie store said 140)
CYA 33 (store said 30)
CH 525 (store said 440)...we both used 44 drops, my kit said multiply by 25, he said as a general rule you multiply by 10
Salt 2500 (going to add salt tomorrow to bring it up to over 3000). Should I wait to add until my PH is good?
Phosphates 150 (from Leslie's)...

I added 1 gallon of liquid stabilizer. It pears I needed 3 gallons, as that one gallon will only raise my CYA by 10 and I need at minimum 50 (from Pentair manual) and 60 according to Pool School.

But the huge issue at hand is the enormous amount of white flakes. While cleaning my tile, I was able to notice that where I thought my plaster was lightening, there were streaks of darker plaster (I have gray plaster) and that the lighter parts were elevated so it makes me think my whole plaster is covered in scale!

 

[chem geek]

Re: What causes calcium scaling in an old pool.

PH needed 7 drops, so I am adding 1.5 gallons over the next two days. (Store added 5 drops)

What does this mean? Are you referring to how many drops of "acid demand" reagent you need to get to a lower pH? So your pH was reading the highest end of the scale (usually 8.0 or 8.2) so could have been higher than that?

 

[Hemess]

Re: What causes calcium scaling in an old pool.

What does this mean? Are you referring to how many drops of "acid demand" reagent you need to get to a lower pH? So your pH was reading the highest end of the scale (usually 8.0 or 8.2) so could have been higher than that?

Yes, that is what I am referring to. From the Taylor calculations in the test kit Manuel, I was guessing my PH was near 9.4 based on how much acid it was indicating I needed. However, I am not even close to being a chemist or a mathematician.

 

[chem geek]

Re: What causes calcium scaling in an old pool.

Yes, the pH was probably around 9.2 to 9.3 if it took 1.5 gallons to get down to 7.5 given your TA level. How in the world did the pH get so high? Even with your high TA and aeration from the SWG the pH shouldn't have gone up past 8.7. Did the pool have new plaster? That can make the pH climb quite high unless acid is added to compensate.

 

[Hemess]

chem geek, I have no idea how it got so high, other than I have not been diligent over the winter in adding acid. My water looks fantastic, but not testing my water enough has caught up with me. Hoping I can get the layers off scale of my plaster.

 

[JamesW]

You can add enough acid to get your pH down to 7.2 in one dose as long as it's added slowly enough to avoid any overconcentrations in any area. You should work down the TA as quickly as reasonably possible. The plaster probably contributed to the pH rise.

I would recommend keeping the pH at 7.2 for a while and brushing frequently.

 

[Hemess]

You can add enough acid to get your pH down to 7.2 in one dose as long as it's added slowly enough to avoid any overconcentrations in any area. You should work down the TA as quickly as reasonably possible. The plaster probably contributed to the pH rise.

I would recommend keeping the pH at 7.2 for a while and brushing frequently.

Ok, I had only been calculating acid additions to get PH down to 7.4. I just added another batch that put me at 2 gallons of muratic acid since last night. I will check PH in a few hours and then see how much more I need, if any.

Any suggestions on how long I should circulate before I check or is it too dependent on pump speed and gallons.

 

[JasonLion]

Let the water circulate with the pump running for at least half an hour after adding muriatic acid before measuring the PH again.