New pool, PH jumps, proper CH level?

[ValleySooner]

What are you chlorinating with? If you are using trichlor or dichlor then your TA is too low, bring it up to about 100-120 ppm.
If you are using bleach, liquid chlorine, cal hypo, or lithium hypo then your TA is perfect but you shoulod bring up your calcium hardness to about 300 ppm.

I'm in a similar situation. My new pool was built three weeks ago, and my ph can jump from 7.6 to 8.0 overnight. My CH is around 200 presently... and I've kept it there because my CSI would be much higher if my CH was around 300 during one of these jumps.

Is my logic faulty? Even if my ph frequently jumps and my CSI would be higher, should I still have a CH of around 300? Or should I wait until my ph is more stable before raising CH further?

 

[JasonLion]

With fresh plaster, you don't want to adjust the CH level for the first three or four weeks. PH, TA, and CH will all be rising rapidly during the first month. If you raise CH too early, it will go up further and end up too high.

 

[ValleySooner]

With fresh plaster, you don't want to adjust the CH level for the first three or four weeks. PH, TA, and CH will all be rising rapidly during the first month. If you raise CH too early, it will go up further and end up too high.

My CH was rising the first two weeks, but leveled off here lately. My TA has been declining with frequent acid additions until I mistakenly added a box of baking soda this weekend. As it turns out, I messed up the settings on the pool calculator. After switching from trichlor to bleach, I didn't update my chlorine source, so it was still suggesting TA levels for trichlor. Oops.

Anyway, thanks for the suggestion!

 

[Guest]

IF your CYA is not that high I would use trichlor for chlorination right now since it will help with the pH rise from the alkaline material being leached from the new plaster.

 

[ValleySooner]

IF your CYA is not that high I would use trichlor for chlorination right now since it will help with the pH rise from the alkaline material being leached from the new plaster.

My CYA currently is 45. I'd like to keep it below 50 if possible.

Here were this morning's test results:
FC 4.0, CC: 0, ph: 7.9, TA: 80, CH: 210, CYA: 45

I've been averaging 15 oz of acid daily to drop my ph to 7.5. The plaster on my pool is now a month old. Should I still keep my CH low for the time being? And how low should I let my TA get? The lower the TA, the more CH I'll need to keep my CSI in line I believe.

Thank you for the advice!

 

[Guest]

Don't micromanage the CSI. It a guideline only. It will also change quite a bit with temperature so unless you have a way to keep the pool at a constant temp all over 24/7 you really can't control the CSI that closely.
This is why there are recommended ranges. If you are in the range (preferabley somewhere in the middle) then you are ok.
The BIGGEST mistake I see pool owners making over and over again is trying to micromanage their water. It can't be done and it does not NEED to be done!

 

[ValleySooner]

Don't micromanage the CSI. It a guideline only.

I do apologize for my error. Perhaps my confusion relates to what the Pool Calculator says with respect to CSI:

CSI is most sensitive to changes in pH. With a plaster pool, it is best to try and get your CSI a little below zero, so that changes in pH won't shift your pool too far towards corrosion or scaling.

To the untrained eye, that appeared to suggest that it was okay to specifically target a CSI value.

This is why there are recommended ranges. If you are in the range (preferabley somewhere in the middle) then you are ok.
The BIGGEST mistake I see pool owners making over and over again is trying to micromanage their water. It can't be done and it does not NEED to be done!

That's good advice. Based on what I read in Pool School and on the forum, I thought there were nuances to managing a newly plastered pool. For example, that ph should be checked and managed daily. That sounds like micromanaging.

Again, I apologize for trying to make this overly complex. I'll just stick to the guidlines and will stop asking dumb questions!

 

[Guest]

Again, I apologize for trying to make this overly complex. I'll just stick to the guidlines and will stop asking dumb questions!

Now that was uncalled for. I was trying to help you and make your life easier since it is not necessary to worry about anything other than keeping the pH down with new plaster. As the plaster cures it is leaching alkaline compounds into your water and the biggest challange is to keep the pH below 7.8 at all times. CSI is not that important at this point if your water parameters are somewhere in the recommended ranges. During the first several months most plaster pools will see an ncrease in CH so the addition of extra calcium is usually not a good idea until things start to stabilize.
Keeping the pH in line is not micromanageing but worrying about and trying to adjust CH and CSI during this period is. Your water chemistry is not stable enough yet.
Anyway, if you knew the actual math behind saturation index the factor that has the biggest impact (smallest change in the parameter makes bigest change in the index) is pH with the second being temperature. pH is fairly easy to adjust. Temperature is more difficult. It takes fairly large changes in TA and CH to make fairly small changes in the SI in comparison so in reality keeping the pH in line IS the most important thing to worry about and until the plaster starts to 'settle down' and the pH rise slows down is all you should really concentrate on. Plenty of time for playing with the other parameters once your water stabilizes more.

 

[JasonLion]

My Pool Calculator has very little space available to explain anything. It is good for doing calculations, but not so good for figuring out what you should be doing. Pool School is a much better place to look for guidance on what to adjust and why. Most people don't need to think about CSI at all. The calculation is provided for those rare cases where it is important.

 

[Guest]

Most people don't need to think about CSI at all.

Exactly!
Jason, you know we have had this discussion before about whether to discuss SI or not and this is the reason why I always said to concentrate on keeping the pH in line and don't mention SI since pH is the main factor that will determine scaling or agresive water conditions, assuming other parameters are somewhere in the accepted ranges. It just complicates things that are really pretty simple.

 

[ValleySooner]

Now that was uncalled for.

I sincerely meant that as no sleight to you! I have a tendancy to make things overly complex in everything I do. And as a new pool owner, I'm full of many stupid questions. I've annoyed my pool builder so sufficiently that I believe most of my emails now go unread.

Anyway, again, I really do appreciate all the help!

 

[ValleySooner]

My Pool Calculator has very little space available to explain anything. It is good for doing calculations, but not so good for figuring out what you should be doing. Pool School is a much better place to look for guidance on what to adjust and why. Most people don't need to think about CSI at all. The calculation is provided for those rare cases where it is important.

Here's what Pool School says about the CSI:

To prevent scaling, you should keep your CSI below 0.6 at all times. Pools with surfaces containing calcium also need to have their CSI above -0.6 at all times to prevent pitting. Vinyl, fiberglass, and painted pools can safely have a significantly negative CSI. The CSI is very sensitive to PH changes. With surfaces containing calcium you normally try to balance your CSI fairly close to zero so that future PH swings will still leave the CSI within these bounds.

It seems consistent with what's explained in the pool calculator -- in that you should try to balance your CSI close to zero so your ph swings don't hurt you! My problem thus far hasn't been finding good information. It's been in attempting to figure out what I should do with it.

Anyway, I'll worry less about CSI and just focus on what I can control.

Thank you!

 

[Guest]

And as a new pool owner, I'm full of many stupid questions. I've annoyed my pool builder so sufficiently that I believe most of my emails now go unread.

Anyway, again, I really do appreciate all the help!

There are no stupid questions. That is how we learn (how do you think I learned what I know!) There is no need to apologize for wanting to learn and asking a lot of questions.
As far as CSI and what pool school says, I agree with you. The info is a bit misleading as to what you need to be concentrating on. I was the voice of dissent when we were writing it because I saw it as a possible complication for a new pool owner. However, I was the minority and was overruled by the powers that be. In a way I am very glad that your confusion on the topic came up because it gives me the chance to say "Told you so!"

(Powers that be, I hope you recognize a joke when you see one!)