Before I add my Duda Diesel Boric Acid...?

[pwa2003]

Because we had some rough plaster upon opening this Spring, I thought I'd try adding borates (via boric acid from Duda Diesel) to hopefully keep it from getting any worse over this coming winter. I'm also hoping to stabilize my pH in general.

My water test results from today show pH of about 8.0 and TA of 100. I know I should lower the TA (I use muriatic acid) before adding the Boric Acid, but I'm unsure how far to go. If I lower my pH to 7.0 with MA, Pool Math app shows my CSI would be -0.68 ("suggests corrosion is likely"). At pH of 7.2, CSI would be -0.49 (still in the "avoid for prolonged periods" range). Those calculations are based on a water temperature of 65F, but with our overnights getting cold, water temp is going down pretty quickly.

What do y'all suggest I do with my chemistry before I add the boric acid?

And I confess I went to the pool store this afternoon to "verify" today's test results (HA!), and they show my TA as 42. That's so wildly different from my reading of 100, I don't even know what to think!

I think I have my Pool Math settings set for TFP members to see my results.

 

[PoolStored]

What do y'all suggest I do with my chemistry before I add the boric acid?

Wait until spring. Do you close the pool?

What is the TA of your fill water?

What do you think the borates are going to do to protect the plaster?

Turn on TRACK CSI, and TRACK TEMPERATURE in pool math. Enter the pool water temp in pool math so we get CSI.

 

[pwa2003]

I understood that the borates would keep the pH from rising "rapidly" in cold water temps, which could've been the source of our rough plaster forming over last winter.

We're on the fence about closing the pool this winter. We closed the last 2 winters, the first one was just weeks after the pool was plastered. We didn't have rough plater the first spring, but the second one we did.

Will test the fill water TA and will turn on those settings.

Thanks!

 

[PoolStored]

I understood that the borates would keep the pH from rising "rapidly" in cold water temps, which could've been the source of our rough plaster forming over last winter.

Why do you think rapid rise in pH would cause an issue with the plaster. Higher pH would cause CSI to rise.

I'm not sure that the plaster issue is due to your chemistry. I ran your numbers from april (see below) and water temp of 70.
ph 8 CSI = .090
ph 7.6 CSI = -.23

I don't see how anything in this range would cause corrosion to the plaster. You would have to run a CSI very negative for months to effect the plaster.

Likely something else is going on.

CSI and LSI - Further Reading

www.troublefreepool.com

 

[PoolStored]

Because we had some rough plaster upon opening this Spring

Can you describe this "rough plaster?" Was it scale, or did it seem like the plaster had degraded (corrosion)?

I, maybe wrongly, assumed degradation/corrosion.

If it was scale like, then yes, borates can help...we have had others here, like @ajw22 experience scale with rising pH over the winter.

 

[pwa2003]

I chimed in on the following thread because it sounds like @bbdude (the original poster there) had a similar over-winter experience to mine:

Winter Scale Build Up?

Hi All - Closed my gunite pool in October and opened in April. Upon opening my pH was high, probably in the 9s. It was 7.2 or so at closing. Our winter was relatively mild so not sure if that had anything to do with the pH. We have swimming temps right now, but my kids are complaining the pool...

www.troublefreepool.com

 

[PoolStored]

My mistake making the assumption about corrosion vs. scale.

@ajw22 found the same, and using borates helped.

The Borate Pool Opening in Aqua Magazine discusses how borates can limit pH rise while a pool is closed for the winter. High pH while a pool is closed can cause scaling. For those that find their pools with very high pH at Spring opening borates may benefit with the pool open or closed.

This can help with how to address the scale:

Calcium Scale - Further Reading

www.troublefreepool.com

As to adding borates, I would get my TA to 60-80 before adding. Also, use "effects of adding" in pool math and Boric Acid as chemical. Note, you will get a pH drop of some size. Adjust your pH above your "after borates" target pH by the amount in effects of adding. Ask me how I know...

 

[ajw22]

You are getting yourself very confused.

And I confess I went to the pool store this afternoon to "verify" today's test results (HA!), and they show my TA as 42. That's so wildly different from my reading of 100, I don't even know what to think!

Pool Stores give you an adjusted TA value that subtracts about 1/3 of your CYA level. Adjusted TA cannot be compared to TFP values and recommendations.

Read TA - Further Reading

My water test results from today show pH of about 8.0 and TA of 100. I know I should lower the TA (I use muriatic acid) before adding the Boric Acid, but I'm unsure how far to go. If I lower my pH to 7.0 with MA, Pool Math app shows my CSI would be -0.68 ("suggests corrosion is likely"). At pH of 7.2, CSI would be -0.49 (still in the "avoid for prolonged periods" range). Those calculations are based on a water temperature of 65F, but with our overnights getting cold, water temp is going down pretty quickly.

Low CSI only causes etching over a long period of time. Your pH will not stay low for very long with a TA of 100 for the CSI to stay low and cause a problem.

You need to get your TA to at least 60-70 before adding borates since borates stabilizes pH and Ta and makes it very difficult to move the TA once you add it. I got my TA down to 50-60 before adding boric acid.

 

[pwa2003]

TA of my fill water is 140.

After adding MA today, I tested 3 hours later (pump running) and my pH was 7.5 and TA 80. With a water temp of 66F, calculated CSI is -0.34.

I guess I keep adding MA gradually (over the next couple of days) until TA falls to 60-ish...? And aerate the water to bring pH back up once at that point? And then add my boric acid? Please confirm or correct me!

Thanks for the explanation of the pool store TA reading. I'll ignore it.

 

[ajw22]

I don't know what you mean by "adding MA gradually".

To lower TA you add MA to get the pH down to 7.2-7.4. Then aerate and get pH up to 7.8-8.0. Test TA and then repeat.

 

[JamesW]

I know I should lower the TA (I use muriatic acid) before adding the Boric Acid, but I'm unsure how far to go.

In my opinion, adding the boric acid first is better than waiting until the TA is lower.

This is because that will allow you to add more acid per dose and the TA comes down faster.

It is counterintuitive because you have to add more acid to lower the pH, which seems like a bad idea, but the amount of acid added is directly proportional to the amount of TA drop.

 

[pwa2003]

I don't know what you mean by "adding MA gradually".

To lower TA you add MA to get the pH down to 7.2-7.4. Then aerate and get pH up to 7.8-8.0. Test TA and then repeat.

"Gradually" as in more than one batch (like you say, test and then repeat). I added 41 ounces of MA this morning to get pH of 7.5 and TA of 80. I know I'll need to add more MA to bring down the TA further.

I was going to ask how high I need to bring pH up to with aeration before adding more MA. Is your suggestion of 7.8-8.0 based on CSI or a chart or...? Pool Math shows ideal target is 7.6-7.8.

What do I want my pH to be when I add the boric acid? I was thinking 7.6-7.8, again since that's shown as "ideal". -OR- I should use Pool Math Effects of Adding like @PoolStored mentioned above.

 

[ajw22]

I was going to ask how high I need to bring pH up to with aeration before adding more MA. Is your suggestion of 7.8-8.0 based on CSI or a chart or...? Pool Math shows ideal target is 7.6-7.8.

The more acid you add, the more TA goes down. You can add more acid going from 8.0 to 7.2 then from 7.6 to 7.2.

What do I want my pH to be when I add the boric acid? I was thinking 7.6-7.8, again since that's shown as "ideal". -OR- I should use Pool Math Effects of Adding like @PoolStored mentioned above.

Doesn't matter that much. Anywhere in 7.4-7.8 range.