Is pH 8.7 acceptable if csi is zero?

[key1cc]

Specifically, in the winter time when no one is swimming, is 8.7 ph going to be a problem in a plaster pool less than a year old if csi is zero?
Cl 6ppm
Ph 8.7
TA 50ppm
Calcium 250ppm
Cya 60ppm
Water temperature 35F
Salt 3200ppm

 

[Bperry]

Specifically, in the winter time when no one is swimming, is 8.7 ph going to be a problem in a plaster pool less than a year old if csi is zero?
Cl 6ppm
Ph 8.7
TA 50ppm
Calcium 250ppm
Cya 60ppm
Water temperature 35F
Salt 3200ppm

How are you measuring 8.7? That’s the likely question because pH meters need to be calibrated, cleaned, and stored carefully to remain accurate. The Taylor kits just read up to 8.2, though I guess you can estimate with the acid demand.

But most people don’t measure anything over winter.

 

[ajw22]

Happy to have your pool as the test bed.

Let us know how it goes.

 

[key1cc]

How are you measuring 8.7? That’s the likely question because pH meters need to be calibrated, cleaned, and stored carefully to remain accurate. The Taylor kits just read up to 8.2, though I guess you can estimate with the acid demand.

But most people don’t measure anything over winter.

I have an Apera700 pH meter with built in temperature compensation, which is good to 2 decimal places. I use 3-point calibration with buffers 4, 7, and 10 to calibrate it regularly. I also use a standard of pH 6.86 to verify it is reading accurately after each reading. I also store the electrode in a buffer solution with a constant pH reading of 3.55. if it changes by 0.02 to 3.57 it provides me an early warning system to recalibrate. In other words, I am very confident my Ph readings are accurate.

I have heard most people don't measure over winter, but as a new pool owner with lots of time on my hands I am curious if csi would be acceptable to follow across all ph ranges or if it is only accurate in a narrow pH range.

 

[key1cc]

Happy to have your pool as the test bed.

Let us know how it goes.

Happy to comply

 

[ajw22]

I am curious if csi would be acceptable to follow across all ph ranges or if it is only accurate in a narrow pH range.

What does "acceptable" mean?

 

[JamesW]

I don’t recommend it, but I don’t know of any harm as long as the CSI is 0.0.

You need to brush the pool regularly to make sure that you are not getting scale and to make sure that the water is thoroughly mixed.

You are really getting beyond the normal levels and you do this at your own risk.

I would limit the pH to a maximum of 8.3, but I can’t give you a good reason for this specific limit.

 

[duraleigh]

What's the point? attempting to maintain that in warmer conditions will surely bring scale conditions to your pool water.......you DO NOT want that.

TFP guidelines have been developed because they work. Manage your water outside those guidelines and you are asking for issues.

Test your pH with a phenol red test.....I wouldn't trust digital.

 

[Bperry]

I have an Apera700 pH meter with built in temperature compensation, which is good to 2 decimal places. I use 3-point calibration with buffers 4, 7, and 10 to calibrate it regularly. I also use a standard of pH 6.86 to verify it is reading accurately after each reading. I also store the electrode in a buffer solution with a constant pH reading of 3.55. if it changes by 0.02 to 3.57 it provides me an early warning system to recalibrate. In other words, I am very confident my Ph readings are accurate.

I have heard most people don't measure over winter, but as a new pool owner with lots of time on my hands I am curious if csi would be acceptable to follow across all ph ranges or if it is only accurate in a narrow pH range.

Is this just an intellectual exercise? Your CH is at the bare minimum for plaster and by increasing it a bit you can keep it at a more normal pH and still get a neutral CSI. If you’re worried about hard water increasing calcium I’d guess you get lots of snow over winter which will mean lots of water replacement anyway?

 

[key1cc]

The reason for this question is that every 4 days my pH goes up to ~8.5 (8.7 if I let it go 5 days) and I adjust it back down to 8.0 with 1 cup of muriatic acid. I asked the questions with the numbers I provided because I am considering adjusting closer to those numbers as the temperature drops.

Currently my numbers are as follow: My csi floats from -0.2 to +0.3 (as I try to keep it between pH 8 and 8.5 to stay within CSI range).
My actual numbers today are pH 8.3, CYA=60ppm, alklinity=50ppm, calcium=625ppm, water temperature is 42, salt is 2600ppm. We have been getting record rainfall lately so I have flexibility to make adjustments if it continues.

 

[proavia]

You are using your pool pump to circulate the water and the pool has not been winterized?

Your last PoolMath logs are over one month old.
Update those with a complete set of current test results.

 

[ajw22]

Don't get so myopic about your CSI.

The pool does not self destruct immediately if the CSI gets out of range. No damage will come from the pool having a negative CSI for 3 months until you open it in April. You can get scaling with a high pH even with what looks like a good + CSI.

It's your pool but my recommendation is stop experimenting with your pool and keep your pH around 7.8 if it is open. Or close your pool and forget about it until April.

 

[xDom]

I didn’t think the pH would get that high?
I saw a chart where the quantity of CO2 in the pool equalises with atmosphere. Giving the pH at different points
It’s basically the Carbonate Alkalinity at different temperatures.
According to the chart the maximum pH should be 7.96.

 

[JamesW]

I didn’t think the pH would get that high?

Plaster gives off calcium hydroxide and calcium carbonate, so the pH can go well over 10.

The problem with saying ok to 8.7 is that the next person will ask "Well, what about 8.9 or 9.5 or 10 or 11" etc. and where does it end?

I would not go over 7.9 for most cases and definitely not over 8.3 at the highest for any pool.

If you choose to go over 7.9, then you are on your own as no one really has much experience with levels at 8.0 and above.

You need to circulate and brush often and thoroughly to avoid scale at the surface of the plaster.

With zero circulation, the plaster and water boundary can get a much higher CSI than in the bulk water and this can lead to scaling even if the water tests show good CSI.

 

[key1cc]

My pool and equipment are fully winterized . During the summer I had to add Muriatic acid every day to my new plaster pool when we kept the temperature in the high 80’s. Now that the temp is in the low 40’s, I add acid every 4 days which is a piece of cake considering what I am use to.

Every 4 days I unlatch a couple straps from opposite corners of my safety cover and drop in a submersible pump in each of the opposite corners and run them for about an hour to mix the acid in. I tested the pH with my very sensitive pH meter several times during the hour and found that it took no more than 15 minutes for the acid to completely mix. But i let run for about an hour anyway for insurance.

 

[key1cc]

You need to circulate and brush often and thoroughly to avoid scale

But how can scale form if I stay in the csi range. Isn’t that one of the main purposes of following csi?

 

[JamesW]

But how can scale form if I stay in the csi range. Isn’t that one of the main purposes of following csi?

With zero circulation, the plaster and water boundary can get a much higher CSI than in the bulk water and this can lead to scaling even if the water tests show good CSI.

 

[xDom]

How are you measuring 8.7? That’s the likely question because pH meters need to be calibrated

Given that pH meters should have to have their probes replaced yearly ( might not be universal but did read that for one model)
How long could you expect a built in pool pH probe to last?

 

[key1cc]

The problem with saying ok to 8.7 is that the next person will ask "Well, what about 8.9 or 9.5 or 10 or 11" etc. and where does it end?

You just hit the nail on the head. That is exactly what I am trying to understand. Essentially…if I always adjust to stay in the csi range, does the pH have upper limits ?

 

[key1cc]

With zero circulation, the plaster and water boundary can get a much higher CSI than in the bulk water and this can lead to scaling even if the water tests show good CSI.

That makes a lot of sense. Thank you for that. Sounds like the key is to circulate at some level of regularity.