Trying to find the balance to reduce acid addition with acceptable CSI

[ckendalls]

Firstly, This group is awesome and the pool stores must hate it. Very helpful.
Here we go...

Our SWG pool is about 10 months old and operational year round here in the Central Florida “mountains”. I probably average 10-15 Oz of MA a day to keep the pH between 7.4 and less than 8.0. I have been hoping by letting the TA drop to 50-60. I would get that pH 7.7-7.8 plateau or at least it would slow down the drift up to that. If I do that though with this CYA level my CSI is pretty negative approaching -0.5.

I guess I could increase CH to help a bit but its still pretty negative at CH 450 ppm. I probably don’t need the CYA level this high because my SWG puts out plenty of Fc for this screened in pool even at ~1% running 8 hrs. But it does seem that this “higher” CYA has also slowed the pH drift up somewhat, probably by reducing the need for more SWG % even more. Some say higher Borate could help and I may go to 70 ppm just to see, but it won’t impact the CSI unless I increase TA or CH and then I’d still be using the same MA acid (20-30 oz) every other day.

So any advice? Raise CH way up?
Maybe go to 70 with borate and see what happens?
Is less than -0.5 really bad if I have enough Calcium in there for the plaster?
Or raise TA and lower CYA and live with the usual acid additions? Is 20-30 oz every other day more than most have to do with SWG pools of this 11K gallon size?

I wouldn’t don’t mind so much adding the MA myself because I check every day anyway (“my lab”), but I can’t get anyone to add acid for me when Im not around and Im not sure how high the pH would go if I was gone more than 4 days or a week or two..

The numbers:

pH 7.5 (for now)
FC 4.5 (pretty stable and more than I prefer but running 1%)
TA 60 (lowest I go so far)
CH 370 (never changes)
CYA 70 (higher than I usually target 50 since the SWG put out even at low %)
Salt 3200
Borate 55 (mannitol tested)
CSI. -0.48 (pretty low)
Temp. 83-89

Thanks for any suggestions on this.

 

[Jimrahbe]

C,

Maybe I just don't understand the problem, but if you let your pH drift up to 7.8, I get a CSI of -.13 and at 7.9, I get -.04, which is perfect???

Why do you keep forcing it down to 7.5 or lower???

What I do is let my pH drift up to 8.0, when it does, I knock it down to 7.7 and let it drift up until it gets to 8.0 again...

As long as my TA is 50 or above, I am happy.

What am I missing..

How often do you run your water features???

Thanks,

Jim R.

 

[RonsPlc]

From what I have gathered through my readings here on TFP, I have heard of new plaster pools having an insatiable appetite for acid in their first year of operation.
I would like to suggest that you keep up with it for the next little while, and that it should settle down on its own given time.
Others around here know better about this than I do though, and will be sure to correct me if I am mistaken.

 

[Jimrahbe]

While it is true that new plaster can cause an increase in your pH for about a year, it is most noticed in the first month.. By the time you get to the 10th month, it has very little effect...

Thanks,

Jim R.

 

[ckendalls]

C,

Maybe I just don't understand the problem, but if you let your pH drift up to 7.8, I get a CSI of -.13 and at 7.9, I get -.04, which is perfect???

Why do you keep forcing it down to 7.5 or lower???

What I do is let my pH drift up to 8.0, when it does, I knock it down to 7.7 and let it drift up until it gets to 8.0 again...

As long as my TA is 50 or above, I am happy.

What am I missing..

How often do you run your water features???

Thanks,

Jim R.

It will still go beyond 8 based on my acid addition tests. It doesn't just hang at 7.7-7.8. You’re right of course.. if it did, the CSi would be OK although with those other numbers I get -0.3 unless I raise TA or CH. I wish it would stay at 7.7-7.8

I don't run the water features every day or when I do not all day. I do have a resistance swim jet system that is usually on no longer than 30 minutes a day.

 

[ckendalls]

C,

Maybe I just don't understand the problem, but if you let your pH drift up to 7.8, I get a CSI of -.13 and at 7.9, I get -.04, which is perfect???

Why do you keep forcing it down to 7.5 or lower???

What I do is let my pH drift up to 8.0, when it does, I knock it down to 7.7 and let it drift up until it gets to 8.0 again...

As long as my TA is 50 or above, I am happy.

What am I missing..

How often do you run your water features???

Thanks,

Jim R.

It will still go beyond 8 based on my acid addition tests. It doesn't just hang at 7.7-7.8. You’re right of course.. if it did, the CSi would be OK although with those other numbers I get -0.3.

That’s where I want to get.

I don't run the water features every day or when I do all day. I do have a resistance swim jet system that is usually on no longer than 30 minutes a day.

I wish it would stay at 7.7-7.8

 

[ajw22]

Plaster pools with a SWG tend to have constantly rising pH. Needing to lower pH every few days is likely normal for your pool. You are not going to get pH to hang at 7.7-7.8.

 

[ckendalls]

C,

Maybe I just don't understand the problem, but if you let your pH drift up to 7.8, I get a CSI of -.13 and at 7.9, I get -.04, which is perfect???

Why do you keep forcing it down to 7.5 or lower???

What I do is let my pH drift up to 8.0, when it does, I knock it down to 7.7 and let it drift up until it gets to 8.0 again...

As long as my TA is 50 or above, I am happy.

What am I missing..

How often do you run your water features???

Thanks,

Jim R.

I knock it down to 7.4 when it hits 8.0 or so because if I only go down to 7.7 I will be adding acid every day. I am hoping to get to a pH under 8 that will hold with an acceptable CSI. A lower TA like 50 might help but the CSi will be even lower. I have seen some that go way high on CH maybe to compensate for a more neutral CSI.

 

[ajw22]

Your pH probably climbs at .1 a day. If you take the pH down to 7.6-7.7 you need to add acid every 3 to 4 days, twice a week.

Try it that way.

 

[ckendalls]

Your pH probably climbs at .1 a day. If you take the pH down to 7.6-7.7 you need to add acid every 3 to 4 days, twice a week.

Try it that way.

I wish it only climbed .1 a day... That’s the problem. It climbs faster. More like .25-.3 a day. Faster when the TA is above 60.

 

[ckendalls]

Plaster pools with a SWG tend to have constantly rising pH. Needing to lower pH every few days is likely normal for your pool. You are not going to get pH to hang at 7.7-7.8.

Yup. That’s probably the reality. Gotta get someone when Im gone for even a few days OR work on the automated acid addition stuff...

 

[ajw22]

Get your TA down to 50 if necessary.

pH climbs quicker from 7.4 then it does from 7.7.

 

[ajw22]

Yup. That’s probably the reality. Gotta get someone when Im gone for even a few days OR work on the automated acid addition stuff...

Just lower pH when you return. pH over 8 for a few days even a few weeks will not damage anything.

 

[ckendalls]

Just lower pH when you return. pH over 8 for a few days even a few weeks will not damage anything.

Thanks much and will do more plotting and experimenting with TA 50 and maybe raise the CH a bit.

 

[ajw22]

Thanks much and will do more plotting and experimenting with TA 50 and maybe raise the CH a bit.

Why do you think you have to raise the CH?

As Jim pointed out your CSI is perfect at pH 7.7-7.9 now. That is where your pH should live the majority of the time.

 

[ckendalls]

Why do you think you have to raise the CH?

As Jim pointed out your CSI is perfect at pH 7.7-7.9 now. That is where your pH should live the majority of the time.

Not sure how Jim got the more neutral number. Am I doing something wrong? See screenshot below. When I use pool math to calculate CSI with these numbers at 7.8 I get a CSI of -0.3 and it would be lower with a Ta of 50. More calcium would get me closer... Also, the water is warmer now. It will be cooler in Oct.-April and still open.

 

[Jimrahbe]

I did not add anything in the borates section.. We generally tell people to not add borates until you've had the pool running for a year or two.. and then with caution...

Did you add borates or do you just think you have borates?

Jim R.

 

[ckendalls]

I did not add anything in the borates section.. We generally tell people to not add borates until you've had the pool running for a year or two.. and then with caution...

Did you add borates or do you just think you have borates?

Jim R.

I added Boric acid a few weeks ago well after the pools chemistry seemed very predicatble. It did seem to slow down the pH drift up a bit when I eventually got to 50 particularly the first week, but no overall difference in acid amounts to get to target pH. I use the mannitol test for Borate level testing.

 

[Jimrahbe]

C,

Sorry, what I know about borates could fit on a pin head with plenty of room left over.. ?

Jim R.

 

[ckendalls]

The Borate addition didn't impact chemistry much maybe a bit slower to drift up... but there is some perceptible change in feel and sparkle that is pleasant.