Winter/cold water CSI

[CavVet]

First winter with TFP...
FC 6
CC 0
pH 7.8
Alk 80
CYA 80
salt 3600
CH 360
water temp 40*f
CSI 0.42

Question: with the 0.42 csi being ‘potentially corrosive to plaster’ should I allow the pH to rise to 8, to keep CSI on the lower end? I was going to lower it to 7.6 in the morning, but am second guessing this now. Let pH go to 8 and maintain there?

As my water gets cooler through the winter months, CSI will continue to be corrosive at my current levels.

Thoughts/suggestions/wisdom?

 

[mknauss]

I think you meant your CSI was -0.42. You are not in the danger zone yet but do not want it to get much lower.

You could lower your pH if you wish. I assume you do not winterize so your pump, etc is still operating.

Take care.

 

[needsajet]

I'll just add that when the water is that cold, everything is in slow motion, and you're fine. If it were mine, I'd just let the pH sit at 7.8/7.9

 

[CavVet]

I think you meant your CSI was -0.42.

Yes sir, I did mean -0.42. I’ve not experienced what ‘corrosive to plaster’ looks like, and don’t want to damage my pool surface.

Lastly, my test kit only measures pH to 8, is there a way to measure above that, so I don’t let it get too high?

 

[duraleigh]

There are pool pH tests that measure to 8.2 (Taylor and others.) Meanwhile, if you go to 8.0, you are too high.

TFP guidelines call for your pool water to STAY in the 7's.

 

[duraleigh]

Staying within the TFP guidelines for all your parameters will automatically keep your CSI in an acceptable place.

 

[JoyfulNoise]

Honestly, I would leave it alone. Plaster corrosion is a slow process and a pool would need to be exposed to water with a CSI lower than -0.6 for months on end before anything noticeable would happen. If you want, bump your TA up by 10ppm and then just keep the pH around 7.8.

Your pool will be fine.