Any Ideas why my pH is so high when I fisrt open the pool?

[JasonLion]

Low PH can dissolve CH out of the pool surface and into the water.

High PH can cause CH in the water to deposit on the pool surface as calcium scaling.

In both cases it isn't just the PH that matters, TA CH CYA borates and water temperature all contribute to the odds of there being problems in either direction. Still, PH is the primary factor and everything else plays a secondary role.

 

[Guest]

Properly done, they should be able to get that finish back to "silky smooth" again. Whatever they used to sand does not sound like the proper machine. You might contact Aquavations (www.aquavations.com) and see if you can speak to them directly. They are a stand up company, and provide a quality product.

Hydrazzo is a strong, durable finish. The extra price you paid sounds in line for the finish you initially had. You can get that back, as the product will allow it to be worked again.

 

[Johnl]

I have a plaster pool and the same problem with the PH going up very high while the pool is closed for the winter. Other people I have talked to with pools don't seem to experience this problem, although they have mesh covers and I have a hard cover for my IG pool. I'm not sure if it makes a difference, I just can't figure out another reason why my PH goes up and theirs seem stable.

Twice we have had a significant amount of scale deposits that had to be scraped off when we opened the pool. Not a fun job. You may be having the same issue if your PH rises over the winter. Last year when I closed the pool I added Scaletec and the pool was fine when I opened it, except for one rough patch by my steps. The PH still went very high, but the scale didn't form.

By the way, my pool is 5 yrs old and the rising PH over the winter has happened every year.

 

[dfiletti]

Can anyone of you chemistry experts comment on the use of Sodium Bicarbonate is stead of, or in addition to Muriatic acid to lower and possibly stabilize the pH, which is currently taking +/- 2 gallon per week to keep in check? I know it will raise given the fact that I use a SWG, so I'll alway need to add some MA, and I have my CYA to 70 now, and run the SWG 20% 24/7, but I was hoping to stabilize the pH rise as much as possible.

Any other input?

Thanks,

Dan

 

[chem geek]

Sodium Bicarbonate will increase the Total Alkalinity (TA) level and make the rate of pH rise WORSE, not better. The reason is that the carbonates in the water have TWO effects: one is that they are a pH buffer which makes the pH more stable, but they are also a SOURCE of rising pH in their own right due to increasing the rate of carbon dioxide outgassing. Basically, pools are intentionally over-carbonated and TA is a measure of that carbonation.

So the way to reduce the amount of acid that needs to be added in a pool is to significantly lower the TA level. Your current TA is at 90 ppm. You can lower it to 70 ppm or even 60 ppm and see if that helps reduce the amount of acid you are adding. If it does, then you should raise the CH level to compensate for the saturation index and can also target a higher pH of 7.7 instead of 7.5. You can also add 50 ppm Borates to the pool to act as an additional pH buffer that will not be a source of rising pH. Your CYA is also low for an SWG pool and a higher CYA of 80 ppm (with an FC minimum of 4 ppm) should reduce the amount of chlorine that is needed. This may also let you turn down the SWG on-time which is the other source of rising pH.

All of this is explained in Water Balance for SWGs though I think you can experiment getting more aggressive with a lower TA. Certainly, the higher CYA level and the use of Borates have helped many.

 

[JasonLion]

Sodium Bicarbonate is baking soda. Baking soda raises your TA level. TA has two effects. At higher TA levels it is more difficult to change the PH. Also, at higher TA levels there is more upward "pressure" on the PH. Last I heard, your TA level was around 90, which is higher than the recommended level for use with a SWG (60 to 80). So, no don't add any Sodium Bicarbonate unless your TA level is much lower than it was before.

2 gallons a week is a lot of acid. You usually only see that in the first month after fresh plaster is applied. Something is going on. Could you post current PH, TA, and CH numbers? Also, what chemicals have you been adding since last time?

 

[dfiletti]

OK here are fresh numbers -I just measured:

Date: 5/27: 22:15
FC: 5
CC: .10 (very little bit of pink, almost imperceptible)
TC: 5.1
pH: 7.6
TA: 80
CH: 500
CYA: 80
Temp: 77
Salt: 3300
SWG %: 20
Pump Cycle: 24/ 7
Filter Pressure: 22 psi
Heater: Standby

Except for the ever increasing CH I like my numbers just now, I guess based on you comments, I should be lowering to TA a bit, bit it's down 10 from the last time I measured a few days back.

As to what other chemicals I have added: None. All I have added to the pool is Acid. Looking at my spreadsheet, actually it's more than 2 gallons per week. Example: 5/13 pH was 7.4 using that as a target I had added 3 gallons to be again at 7.4 on 5/21 -so it's +/- 3 gallons per week. This is consistent with the previous week as well. I'd really like to reduce that acid consumption.

Dan

 

[dfiletti]

In the interest of full disclosure, I should add I guess, that most recently, I DID add 1.5lbs of CYA on 5/21 and 6.5 lbs on 5/15. Right after I opened the pool, on 5/10 I added 1 gallon of "Beautec". I also added 40 lbs of salt back on 5/14. Other than that (and of course 14 gallons of MA -so far) nothing has been added to my water this year.

The guy I buy my acid from thinks I may be trying to dispose of a body or something -he does kind of look at me sideways.

Thanks for the help folks.

Dan

 

[mamasproject]

In the interest of full disclosure, I should add I guess, that most recently, I DID add 1.5lbs of CYA on 5/21 and 6.5 lbs on 5/15. Right after I opened the pool, on 5/10 I added 1 gallon of "Beautec". I also added 40 lbs of salt back on 5/14. Other than that (and of course 14 gallons of MA -so far) nothing has been added to my water this year.

The guy I buy my acid from thinks I may be trying to dispose of a body or something -he does kind of look at me sideways.

Thanks for the help folks.

Dan

Wow....that is a lot of MA!!! Are you sure you are buying full strength and not the 1/2 strength MA? I opened on April 17th and have used 3 gallons of MA and my pool was built just last fall!

Where I buy the MA- Sears Hardware- they ask me for my driver license, why? You have to be 18 to purchase MA! I'm flattered they asked for ID....but I do not look 18!!! LOL!!!

 

[dfiletti]

I buy it in 5 gallon 'gerry jugs' or that's what I call them, from a local pool store. Her is the cheapest guy around for acid; $19.00 / 5 gallon fill, after the first $6.00 deposit. I guess he could be cutting it. Is there a way to test acid strength?

It sounds like a lot of acid but it took 8 gallons to get the pH from it's 11.x perch to a more reasonable 7.4.. Since then it's been just under three gallons / week -which is still quite a lot.

 

[dfiletti]

Folks-

I have been exchanging emails with the good folks at Aquavations and I would like, if possible some feedback on the points their tech guy is making to me.

He said the following:


"It is imperative to check and adjust chemicals in a covered pool during the closed months when ever the water isn’t frozen. There is no substitute for sound technical water balance to the Langelier Saturation Index. It isn’t realistic to expect water to remain balanced when unattended for 7 months and not have problems. Electrolytic saltwater chlorination generates sodium hydroxide as a by-product. Sodium hydroxide has a pH or 13-14.

Adding acid to lower the pH drives the alkalinity down and needs routine adjustment. Low alkalinity leeches the calcium out of cement and raises the calcium harness in the water to high levels over 350 ppm causing saturation indexes that are difficult to manage."

I responded with the following:

"Thanks for your response. I target a pH of 7.4 and an alkalinity of 60-80. Only once last summer was my alkalinity 50 and this was after adding 3 gallons of MA. All other readings were within, or above my target.

I kick myself for not measuring my alkalinity ad soon as I opened the pool. But given that it took 8.5 gallons of MA to get my pH to 7.4, I can infer that my alkalinity was very HIGH not low over the winter. My very first TA test, the day after after having completed adding 9.5 gallons of MA, showed a TA of 90!

Reverse engineering the TA from how much acid it took to get the pH under control means that my TA was over 200! A far cry from bring too low. Please correct me if my understanding of this is incorrect.

Based on your comments, and my inferences, I would expect little to no calcium leaching based on low TA. Can it, will it leach with HIGH pH and TA or again, am I assuming my TA was high incorrectly?

Regarding treating the water over the winter? How do you recommend I do this? Can I add acid when the pump is not running without damaging the Hydrazzo?

Regarding your point about SWG producing a high pH byproduct, I believe this has a great deal to do with why I still need a surprising amount (~3 gallons per week) to keep my pH in check. However the SWG was not running, indeed it was not even connected over the winter, yet my pH still went up from 7.4 to 11.3. How can you account for this?"

I would greatly appreciate direction from any of the chemists on this list. Am I wrong in my TA assumptions, they were lifted directly from Chem Geeks post.

Also, as to his assertion that "There is no substitute for sound technical water balance to the Langelier Saturation Index" Based on an on-line calculator I found, I understand I will need to be capturing total dissolved solids (TDS) and Ca to make this calculation.

I am completely guessing here, but does TDS = Combined Chlorine and Ca = Calcium Hardness or is there some other testing I need to be doing to gather these?

Last question, what is the down-side of high CH? I know to lower it will required a water exchange, but is it bad in a plaster pool to have it too high, will it make balancing water chemistry tough? How so?

Again, I really appreciate your help folks.

Thanks,

Dan

 

[JasonLion]

"It is imperative to check and adjust chemicals in a covered pool during the closed months when ever the water isn’t frozen. There is no substitute for sound technical water balance to the Langelier Saturation Index. It isn’t realistic to expect water to remain balanced when unattended for 7 months and not have problems. Electrolytic saltwater chlorination generates sodium hydroxide as a by-product. Sodium hydroxide has a pH or 13-14."

Well, yes and no. If the water is below 50 degrees you can usually get away with ignoring it. Above 60 you definitely need to test and adjust. Between 50 and 60 it can go either way. A SWG is PH neutral, has no long term effect on the PH in and of it's self. However, a SWG will cause aeration, which can raise the PH quite dramatically in some situations.

We tend to use the calcium saturation index (CSI), instead of LSI, but the idea is the same. With a plaster pool, you always want to keep your CSI/LSI between -0.6 and +0.6. Very low CSI will cause plaster damage, while very high CSI will cause calcium scaling. You can calculate your CSI using the Pool Calculator, see the link in my signature.

Based on your comments, and my inferences, I would expect little to no calcium leaching based on low TA. Can it, will it leach with HIGH pH and TA or again, am I assuming my TA was high incorrectly?

You can't look at just TA, you need to consider the full set of readings to know how it will affect the plaster. Still, you are basically correct here. High TA makes it very unlikely that there would be any calcium leaching.

Regarding treating the water over the winter? How do you recommend I do this? Can I add acid when the pump is not running without damaging the Hydrazzo?

You have to have some circulation to be able to add any chemicals. That usually means taking the cover off.

Regarding your point about SWG producing a high pH byproduct, I believe this has a great deal to do with why I still need a surprising amount (~3 gallons per week) to keep my pH in check. However the SWG was not running, indeed it was not even connected over the winter, yet my pH still went up from 7.4 to 11.3. How can you account for this?"

It isn't the SWG that is causing the PH to rise. High TA causes the PH to rise, and a SWG can accelerate that process, but if your levels are balanced correctly a SWG doesn't need to cause the PH to increase. If I remember from your previous posts, I believe there were additional PH increases that we couldn't account for.

I am completely guessing here, but does TDS = Combined Chlorine and Ca = Calcium Hardness or is there some other testing I need to be doing to gather these?

TDS doesn't really have anything to do with combined chlorine, it is a separate measurement. You don't need to know your TDS to calculate CSI/LSI. Ca is calcium hardness, though we always call it CH.

Last question, what is the down-side of high CH? I know to lower it will required a water exchange, but is it bad in a plaster pool to have it too high, will it make balancing water chemistry tough? How so?

High CH levels, if not compensated for with your other levels, will lead to calcium scaling.

 

[dfiletti]

Thank you Jason. Very Helpful. It's fairly clear to me then that I need to exchange a bunch of water (~40% or ~10,000 gallons). Before I do, I want to get to the bottom of what's causing the CH to go over 500, and see it I can't do something to prevent it.

I'll report back what I hear from Aquavations.

Thanks again.

Dan

 

[duraleigh]

Should this be in "The Deep End"?