New Plaster with pH drift but want to close

[BMoreE]

I love these forums - you guys are awesome. I had a question, but searched first and viola... the answer exists from 11 years ago: Monitor pH after closing pool with new plaster?

My scenario is exactly the same: new pool 3 months ago, pH goes up .4-.6 in days, it's time to close and I'm uncertain what to do.

The IP didn't follow up with the question posted back to them when they asked about how one would continue to add acid after winterizing. I'm located in Maryland, so we definitely are subject to hard freezes so I wouldn't want to keep a pump in the pool to circulate any acid I need to add over the winter.

Anyone have any idea if just "stirring" the pool after adding acid would suffice to raise the pH? Kinda a pain (will need to open cover in multiple spots) but will do what we gotta do.

 

[ajw22]

What is your pH and TA?

Close as late as possible. You can keep your pool open for a few more weeks. My pool in NJ will be closing October 18 and I would keep it open later but I need to close it before too many leaves fall. The trees around the pool make it unpractical to keep it open later.

Lower your TA to 60 and at at closing lower your pH to 7.2.

Then open your pool next year as soon as youa re past nighttime freezing temperatures.

 

[BMoreE]

pH is all over... I pull it down to 7.4 with 8-16oz of muriatic, but within 2-3 days it's back up to 8.0+. Same problem as lots of posters have had with needing constant acid with the new plaster.

So my question is really if adding acid over the winter is necessary, and how to ensure it mixes in; it seems others have answered the fact that this is just standard behavior for when new plaster is curing. I found one thread where someone in the same situation closed/opened, and found their surface covered with "crystals" (and mega-high pH) and had to acid/brush them off to get back to normal, so I'm trying to avoid that.

Other data:
TA 90
CH 490
FC 4.0
CYA 10

 

[ajw22]

So my question is really if adding acid over the winter is necessary, and how to ensure it mixes in;

There is no way of knowing if it is necessary or if it is really helping.

The problem is pool water stratifies into layers when left still over time. The heavier water with salt and calcium and other solids sinks to the bottom. Fresh runoff water floats on the top. So when you check the pH which layer of water are you pulling water from? And then when you pour acid in the acid is heavier then water and will sink to the bottom.

Unless you can get a good mix to breakup the water layers and then to mix the acid you may be creating areas of low pH in your pool while areas of high pH exist in other areas.

it seems others have answered the fact that this is just standard behavior for when new plaster is curing. I found one thread where someone in the same situation closed/opened, and found their surface covered with "crystals" (and mega-high pH) and had to acid/brush them off to get back to normal, so I'm trying to avoid that.

That is the problem of high pH raising the CSI and causing scale to form.

Lower your TA from 90 to 60 before closing and lower your pH to 7.2 at closing. That lowers the pH/TA equilibrium point and will keep your pH from rising as high as it otherwise would. See the table at the end of PH TA Relationship - Further Reading

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

 

[JamesW]

Other data:
TA 90
CH 490
FC 4.0
CYA 10

Did you add this much calcium or did it rise on its own?

 

[BMoreE]

I did not add calcium, so presumably that came out of my walls. And given this season it held steady in that 450-475 range, I'm hoping that process was all that happened!

 

[Newdude]

The problem is pool water stratifies into layers when left still over time. The heavier water with salt and calcium and other solids sinks to the bottom. Fresh runoff water floats on the top. So when you check the pH which layer of water are you pulling water from?

+1. Last winter I did some experimenting using 3/4 electric PVC to get a 'bottom sample'. At the surface my salt was 0, at 2ft it was 600 and at 7.5 ft it was 3000. FC had a similar variance.