pH Rising Despite Low Alkalinity

[MM32]

Hi everybody,
Earlier this season when my pool construction was just completed, the pH and alkalinity of the pool water was initially very high. The alkalinity was up around 200ppm at the end of May. Over time I lowered the pH/alkalinity with muriatic acid and recently the alkalinity kind of leveled off at 60 ppm. The last time I added MA was about 2 weeks ago and the pH dropped to about 7.4. It has slowly been creeping back up again and is at about 8 as of this morning (using the comparator block so I’m estimating about 7.9 or 8). This same thing was happening a few weeks ago when my alkalinity was at 80ppm and so that’s why I added MA again about 2 weeks ago and dropped the alkalinity to 60ppm.

Is this ok if the pH stays around 8 or is that too high? Should I lower the pH with MA again at the risk of running the alkalinity below the ideal range? I’ve hear SWGs run the pH high but not sure at what point it’s an issue or if around 8 is acceptable. Let me know what you think, thanks as always!

 

[cwswifty]

Use Pool Math to calculate your CSI. That is what tells you when you need to lower pH and make other adjustments. Being at pH of 8 is not a problem as long as your CSI isn’t too high. I try to stay between -.30 and 0.00.

 

[MM32]

Use Pool Math to calculate your CSI. That is what tells you when you need to lower pH and make other adjustments. Being at pH of 8 is not a problem as long as your CSI isn’t too high. I try to stay between -.30 and 0.00.

How do I calculate CSI? Is there somewhere in pool math that shows me or do I need to do some calculation?

 

[cwswifty]

How do I calculate CSI? Is there somewhere in pool math that shows me or do I need to do some calculation?

Pool Math does it for you. Turn on “Track CSI”.

 

[MM32]

Got it thanks for your help. So I think if I raise my calcium hardness to like 225 I’m in good shape from a csi standpoint. At that point I don’t have to be concerned with the pH being at 8 or higher I guess? I don’t want to open myself up to the possibility of getting algae.

 

[MM32]

Or am I better off increasing the alkalinity instead of calcium harness or a combination of both?

 

[proavia]

What is the pH, TA and CH of your fill water?

pH, TA and/or CH really have nothing to do with getting algae. Allowing your FC to get below minimum based on your CYA (FC/CYA Levels) can produce algae.

 

[cwswifty]

Or am I better off increasing the alkalinity instead of calcium harness or a combination of both?

The title of this post tells me that rising pH is a concern of yours. Keeping TA lower (as low as 50) will slow the pH rise. As stated above, algae takes hold when your FC/CYA ratio is below minimum.

 

[Bperry]

Or am I better off increasing the alkalinity instead of calcium harness or a combination of both?

pH of 7.8 or 8.0 is fine. Above that is where you want to lower it back to 7.8. But note that pH will ALWAYS rise eventually. It’s never going to reach a place where you don’t need acid anymore. That’s just pool life. Don’t lower the TA anymore than 50ppm.

 

[MM32]

What is the pH, TA and CH of your fill water?

pH, TA and/or CH really have nothing to do with getting algae. Allowing your FC to get below minimum based on your CYA (FC/CYA Levels) can produce algae.

My fill water has a pH of about 7.3, TA of 90 and CH of 100. I’m assuming based on this you would add CH increaser rather than raise the alkalinity to keep my csi within range?

 

[wireform]

With a heater the recommended CH is 200 which poolmath shows below that. You can add more if that will bring the CSI to recommended levels for the SWCG. .0 to -.03

 

[MM32]

pH of 7.8 or 8.0 is fine. Above that is where you want to lower it back to 7.8. But note that pH will ALWAYS rise eventually. It’s never going to reach a place where you don’t need acid anymore. That’s just pool life. Don’t lower the TA anymore than 50ppm.

Thank you! So if I keep having to lower the pH the alkalinity will continue to fall correct? So should I bank on thr fact that eventually I will have to increase the alkalinity at some point? This pool life is getting confusing lol

 

[proavia]

You have a vinyl liner - any CSI of 0.00 or less is fine.
With a gas heater, many manufacturers required a CH of 200 minimum.

If TA is 60-70, pH rise will slow down. Let pH hover around 7.8 to 8.0 once TA is 60-70.
With a fill water TA of 90, your TA will rise naturally with water additions.

 

[wireform]

You will probably never get to the point of the TA being low. At some point and every pool is different there will be a happy spot where the PH will move very little and not necessarily only when the TA is a rock bottom.

 

[JamesW]

I’m assuming based on this you would add CH increaser rather than raise the alkalinity to keep my csi within range?

For a vinyl liner, the only concern is high CSI.

Low CSI does not matter.

Keep the CSI at -0.6 to -0.3.

Keep the pH at about 7.8 to 7.9.

Do not lower the pH until it hits 8.0 and only lower it to 7.9.

 

[Bperry]

Thank you! So if I keep having to lower the pH the alkalinity will continue to fall correct? So should I bank on thr fact that eventually I will have to increase the alkalinity at some point? This pool life is getting confusing lol

The pH rise may slow to a point where you need to add very little acid each time and then fill water will add some TA which may make the pH rise faster. Like said above, You probably won’t ever need to raise the TA.