pH woes

[mikester]

I've been trying to balance everything according to the sticky for SWG water balance, and I'm having trouble keeping my pH swings under control. We just had the pool replastered about 8 weeks ago, so I'm guessing that's part of the problem, but it seems like things should be leveling out by now.

Here are my levels as of tonight:

FC - 3 ppm
CC - 0
CYA - 50 ppm
pH - 8.0
Alk - 120 ppm
Calcium - 250 ppm

I know CYA is low - it was at 40ppm last week, and I've been slowly raising it. I added more stabilizer tonight that will hopefully get it above 60ppm after it dissolves. Getting this raised up should allow me to dial down my SWG from the 35% it runs at now, which I guess will help my pH swings a little.

I've been adding 1/2 gallon of acid every 2-3 days, which will bring the pH down to 7.2-7.4, and within 2-3 days it's up to 8.0 again. It's not as much as I had to add right after the replaster job, but it still seems like a lot.

I added another gallon tonight and am running the spa blower and waterfall for aeration, hoping to lower the Alk more. I'm also going to look into adding borates. Is there anything else I should be doing? Is this normal because of the plaster curing, and if so how long can I expect to keep dumping so much acid in the pool?

 

[JohnT]

The SWCG and the plaster are ganging up on you. It will take a lot of acid to keep up.

 

[JasonLion]

Keep working on lowering TA. You can bring TA down to 60 or 70 to minimize the PH increase from TA+aeration. The plaster curing will continue to raise the PH for up to a year.

 

[mikester]

Do you think adding borates at this point would help the pH to not rise as quickly, or is it a lost cause until the plaster is finished curing?

 

[duraleigh]

Mike,

Welcome. chem geek states that while borates will slow the rate at which the change occurs, the total consumption of acid will remain the same. Quite frankly, I need to reread his post on that but I'm pretty sure the total amount of acid you use remains the same regardless of borates.

I would suggest borates as something to address at a later time and to focus on getting a really good handle on keeping your basics in line. It won't take you long to get a feel for what you need and to learn the "rhythm" of your own pool. Then I would address borates.

 

[Guest]

Borates and lowering the TA are not going to help much with the acid demand caused by new plaster (although they will help to some extent at keeping it a bit more stable but when you need to add acid it will be a larger amount). Just keep testing the pH daily and adding acid.

 

[mikester]

Would reducing the amount of aeration help with overall acid demand, or would it just stall the inevitable (i.e. alkalinity would build up and I would have to add more acid later to bring it down)?

I'm currently running my pump 8 hrs/day, and with the spa overflow and a couple of the jets pointed towards the surface it gets a LOT of aeration. Should I try to tone that down a little to save on acid?

 

[Guest]

Mike,

Welcome. chem geek states that while borates will slow the rate at which the change occurs, the total consumption of acid will remain the same. Quite frankly, I need to reread his post on that but I'm pretty sure the total amount of acid you use remains the same regardless of borates.

As someone who has had borates in their pool for a few years now and from the data from my customer's pools with borates I would have to disagree with chemgeek here and say that borates DO reduce acid demand, however, with new plaster they are not going to have much impact. Best course is to lower the TA as suggested, raise the CYA to closer to 80 ppm (this will allow you to run at a lower output percentage and help reduce pH rise) and keep very close tabs on pH. Testing it daily is a good idea for the first few months with new plaster.

 

[Guest]

Would reducing the amount of aeration help with overall acid demand, or would it just stall the inevitable (i.e. alkalinity would build up and I would have to add more acid later to bring it down)?

I'm currently running my pump 8 hrs/day, and with the spa overflow and a couple of the jets pointed towards the surface it gets a LOT of aeration. Should I try to tone that down a little to save on acid?

Get your TA down first and then try to have as little aeration as possible. Raising the CYA will also help create less aeration in the cell itself since you can run it at a lower percentage.

 

[chem geek]

As someone who has had borates in their pool for a few years now and from the data from my customer's pools with borates I would have to disagree with chemgeek here and say that borates DO reduce acid demand.

To the extent that using borates let you lower the TA, then that would be another mechanism in addition to algae prevention with lowering of the SWG output. Otherwise, to have less total acid per time there may be something else going on, perhaps with borates interfering with the carbon dioxide outgassing (even at the same TA level)...sounds like another experiment!

 

[Guest]

As someone who has had borates in their pool for a few years now and from the data from my customer's pools with borates I would have to disagree with chemgeek here and say that borates DO reduce acid demand.

To the extent that using borates let you lower the TA, then that would be another mechanism in addition to algae prevention with lowering of the SWG output. Otherwise, to have less total acid per time there may be something else going on, perhaps with borates interfering with the carbon dioxide outgassing (even at the same TA level)...sounds like another experiment!

One of the claims for borate products in the early patents is that they reduce the CO2 level in the water and that is, in part, where their algaestaic effect comes from.