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I Could Use Some Help With My Ph Battle


stomper4x4
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I thought I had this all figured out but I guess not. I have a new tub. On the first go around I battled with the ph. I was adding way too much PH down and the next day the PH would be back up to 8.0+ . I did this for about a month and finally my Taylor K2005 test kit came in.

So I finally got the PH to stabilize after using the more accurate testing methods.

Ok so it was time to change the water and I did so about a week ago and now I'm having the same problem again...High PH.

Here is a test example.

TA- 130PPM

PH- 8.0

CH- 210PPM

Ok so I add regent R-0005 dropwise and it takes 3 drops to get the ph to 7.6. So I'll add 1.5 TBLS of PH down Sodium Bisulfate 93.2%.

Then a while later I test and everything looks good and say it about 8:00pm. By 4:30PM the next day the PH is back up too high and I didn't use the tub during this period.

In short I keep adding ph down and the ph goes right back up the next day with or with out use of the tub.

The first time I went through this I was using way too much PH down for too long and ended up having a High level of dissolved solids. Thus the need for the water change.

I have read that this problem is tricky to deal with at this form and have read how to deal with it but the tricks don't seem to work for me. Like for example the trick where you raise the TA a little to high on purpose so when you bring the ph back down to where it needs to be the TA well be good as well. I tried this twice and no dice.

For what it's worth my TA and CH are stable but that darn ph just goes right back up very quickly.

I hope this is enough info to give you a idea of what I'm doing over here.

Can anyone make me understand how to manage this problem better with out wasting so many chemicals?

I cant check back to this post until around 5:00pm tomarrow. Thanks

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A few questions:

1) Do you keep a cover on your hot tub when not in use and how long is it uncovered during the time that the pH rises?

2) Do you keep the jets on or have other aeration during the time you see the pH rise? You said the pH rose when it wasn't in use, but wasn't sure if that meant the jets were off during that period of time. Is your hot tub outside and was it windy when the pH rose (assuming there was no cover)?

3) What kind of sanitizer are you using? Is it bleach or Dichlor, Bromine or something else (small SWG)?

The most likely cause for your rise in pH is the combination of a high TA and high aeration. TA measures Total Alkalinity and that is mostly from carbonate in the water (you probably added sodium bicarbonate or baking soda to the water initially) and that essentially makes your spa "a lovely carbonated beverage" so to speak. It has a lot more carbon dioxide dissolved in it than is found in the air so it outgasses it. When this happens, it makes the pH rise (ironically, the TA measurement stays the same, and I won't go into the technical reasons as to why this is true).

IF the pH rise is due to the outgassing of carbon dioxide and not to some chemical addition to your spa, then LOWERING your TA is the answer to your problem. This is ironic because TA is normally considered to buffer pH, but it turns out that the effect of pH rise from too high a TA outweighs the lower buffering effect from a low TA.

There are two ways to lower your TA. First, you could drain and refill your spa and add less baking soda to get to 70 ppm. That's the expensive approach since you need to add chemicals, but it is relatively fast. The second option is cheaper but requires some patience. It is to lower your TA in your existing water and the way you do that is to lower your pH significantly, to around 7.0 (or at least 7.2) assuming your test kit reliably measures that (i.e. that it isn't the lowest measurement on the pH scale of your test equipment) and keep adding acid to keep the pH low AND aerate your spa with all the jets on and pointed up. This will bubble out the carbon dioxide which has the pH rise and your adding acid lowers both the pH and the TA -- net effect is lowering of TA (removing carbonate from your water). When the TA measures a low value, such as 70 ppm, then stop adding acid and let the pH rise by just aerating. The pH should now settle down and be more stable in the 7.5 region or thereabouts. You might still need to add acid periodically, but probably a whole lot less.

Also, you have been using sodium bisulfate as your acid and that increases sulfates in your water, which isn't horrible but you could also (carefully) use muriatic acid which would add chloride to your water. Yes, you increase your TDS either way, but chloride is very benign and would just make your spa more like a salt pool. Of course muriatic acid is a harsher chemical, mostly because it's a concentrated liquid that somewhat fumes.

Since aeration is also a factor, after you get your TA low you should keep your hot tub covered when not in use and keep the jets off as well. That should significantly cut down the pH rise especially combined with the lower TA.

Good luck and definitely keep us posted on your progress and if this helps. It has worked for others with pools (especially those with SWG systems) and a few with spas (on another forum).

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I agree 1000% (NOT a typo) with chem_geek! He said it better than I ever could! The only caution I would give is about using muriatic acid in the spa. While everything he said about it is true an average sized spa of say, about 400 gallons would usually need the acid measured out by the teaspoon! I personally don't want to try and do that! While dry acid will add sulfates to the water and raise the TDS in an undesirable way it is certainly much safer and easier to measure in the small quantities needed for a spa. (Unless, of course, you want to predilute some muriatic acid and compute how much you need from the dilution. Chem_geek, this is right up your alley! ;)

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waterbear, thanks for the caution on Muriatic Acid. I forgot that the tub is small and would require very careful small measurements of acid addition.

One thing that bothers me a little bit with this situation is that there was no TA drop seen during the pH rise, acid addition cycle. The drop would be quite small but over time should have been noticeable. So it is possible that there is some other source of pH rise so I have another questions:

What is your new spa made of? Is it plastic or is this some sort of in-ground plaster/gunite spa? If the latter, then at least some of the pH rise is likely from the curing of the plaster/gunite (concrete). Or does your spa have new tile in it with grout? That would also cure and the curing of concrete causes a significant rise in pH as it absorbs water and releases calcium hydroxide. Anyway, it's just another thought.

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One thing that bothers me a little bit with this situation is that there was no TA drop seen during the pH rise, acid addition cycle. The drop would be quite small but over time should have been noticeable. So it is possible that there is some other source of pH rise so I have another questions:

What is your new spa made of? Is it plastic or is this some sort of in-ground plaster/gunite spa? If the latter, then at least some of the pH rise is likely from the curing of the plaster/gunite (concrete). Or does your spa have new tile in it with grout? That would also cure and the curing of concrete causes a significant rise in pH as it absorbs water and releases calcium hydroxide. Anyway, it's just another thought.

What jumped out at me is that he is using an acid demand test to drop his pH down to only 7.6. I don't believe that this small drop in pH will make any appreciable (or measureable) dent in the high TA of 130 ppm! Now if he were to drop his pH down to around 6.8 or 7.0 then there probably will be a decrease in TA that would be measurable. Or if he continutes to monitor his TA over a period of months while lowering his pH to 7.6 then he might see a measuable drop in TA. Just my 2 cents worth.

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First off thanks guys for the help. Very cool of you to take the time.

chem geek: I do use a cover and the only time the cover is off is when I'm in the tub. It's cold here. The PH rises when the cover is on. I use the tub once per day for about 45 minutes and sometimes twice for 45 minutes. The cover is on all the rest of the time.

I always turn of the air to the all the jets. During the filtration cycle no aeration occurs. It has been windy but the cover is always on.

I'm using Spa guard Bromine concentrate. The tub has a ozonator as well.

The tub is acrylic.

Can you explain why you say my TA is too high. I thought 130PPM was in the range. Or are you just saying that it's to high for my conditions.

Should the TA be set to where ever it works best with the ph. I don't use the test strips any more but the graph on the back of the bottle says 120 -150ppm is ok range. I'm at 130ppm so can you explain this to me so I understand better. I get the feeling that your saying I can sacrifice the TA a little to achieve a balance water.

Let me know if you need any more info from me.

I'll adjust the ph down extra to try to bring the TA down to around 70PPM and then I'll attempt to get the ph under control.

Thanks again both of you .

BTW are you guys like rocket scientists......

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Well, with how you answered the questions, I'm not as certain that the spa being overcarbonated is the cause. If you measured the pH AFTER your 45 minute session and put on the cover and then measured the pH just BEFORE your next 45 minute session and saw the pH rise, then that would tend to invalidate what we think is going on. However, you probably measured the pH at two points in time straddling one or more 45 minute sessions, and if that is so then the total of 90 minutes of strong aeration with high TA per day could certainly lead to a strong pH rise. So, let's try what we suggested (i.e. lowering your TA) since if it doesn't work it's trivial to increase your TA back up (though still probably not to 130).

As for "too high" in TA, the recommendation of 120-150 ppm is, no question about it, too high. Somebody probably thought that with such a small water volume in a spa that extra pH buffering would be a good thing, but they forgot that the pH buffering using sodium bicarbonate also has the side effect of wanting to increase pH. And yes, technically, your TA is too high for your conditions. Someone with a pool that has a cover on it (like I do, with an electric cover) and no aeration to speak of (no waterfalls, upward jets, or water features) could probably live with 120 ppm TA. This would be especially true if an acidic source of chlorine, such as Trichlor tablets, were used. However, with a somewhat neutral chlorine source and without a pool cover, even a pool shouldn't have much more than 100 ppm TA and 80 ppm TA is better. In situations where there is aeration, such as with a waterfall (or an SWG that generates hydrogen bubbles), even lower TA, but generally above 50 ppm TA, helps keep pH more stable.

This concept of lower TA actually stabilizing pH is one of the hardest and most counterintuitive things I have encountered in pool water chemistry. Even though I understand the chemistry of what is going on, it is still quite strange. I guess the best way to understand it is to think of higher TA doing two separate things. On the one hand, higher TA buffers the pH so that for a given amount of acid or base that is added, the pH moves less at higher TA than at lower TA. On the other hand, a higher TA represents more bicarbonate in the pool including dissolved carbon dioxide and this amount is quite a bit higher than found in air so it outgasses. When this happens, it makes the pH rise. Technically, HCO3(-) + H+ --> H2CO3 --> H2O + CO2(g) so you can see that a hydrogen ion gets removed from the water as carbon dioxide is outgassed. pH is just a measure of hydrogen ion in the water with lower pH having more hydrogen ion so with less hydrogen ion the pH goes up (the opposite direction is due to the fact that pH measures the NEGATIVE of the logarithm of concentration which was probably defined that way so that the pH numbers would normally be positive in value). I'm not going to try and fully explain why the TA doesn't change since that is even more complicated, but is essentially based on the fact that each species in the first part of the equation affects TA in opposite directions so they cancel out (just as their charges cancel out).

It turns out that the pressure of high TA on increasing pH outweighs its extra buffering capability so that IF the primary source of pH change is from the carbon dioxide outgassing, then lowering the TA will lower this pH rise effect by more than the reduced buffering at lower TA. So the net result is that lower TA has less of a pH rise.

Clear as mud? Let's just try it out and see what happens. We're all practical people and whatever works is what is most important. I'm just a geek and like to understand what's going on more technically in the hope that I might find some solutions that I otherwise wouldn't have if I didn't possess the extra knowledge.

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Wow!! Thanks!! You explained that so eloquently that I think I can get a handle on how this works.

I'm going to bring down that TA say around 70PPM.

I think it stinks that the test strip container recommends TA levels that might not work for all situations.

I have a feeling that I well get this under control now and be using way less product.

One again thank you big time!!

I well check back and let you all know how the battle goes.

Jason

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This morning before going to work I lowered the ph again but didn't have time to check the TA.

Well I lucked out. The TA came down today.

I just tested after reading your last post and here are the stats.

TA- 70-80 PPM

PH 7.6

CH 210 PPM

Normally I'd be raising the TA right now and starting the ph battle again but now I know the TA is just fine where it is.

I didn't get a chance to hop in the tub tonight but I well test in the morning and after work then I'll list the new stats.

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The reason your bottle of test strips said that the TA should be between 120-150 (and something that you did not make clear and I know I made an assumption otherwise and I think chem_geek did too) is because you use bromine for sanitation. I assumed you used chlorine since you have a Taylor K-2005 test kit. This kit is usable with bromine but I personally would get a Taylor K-2106 kit which is made for bromine and uses FAS-DPD testing which is far superior and much easier to read than DPD testing.

Back to the reason for a higher TA with bromine, actually 2 simple reasons

1. Most people on bromine use tabs which are acidic

2. most people on bromine shock with MPS (non chlorine shock) which is acidic.

The problem with this is that if you use a 2 step bromine system without tablets (only use sodium bromide in the water to create a bromide reserve) and 'shock' with liquid chlorine(bleach) and/or use ozone ( which will lower the amount of shock needed so if you use MPS you will be using a lot less) then the drop in pH and TA does not occur in the same way and your pH will tend to shoot up. The good part is that bromine does not care as much about pH as does chlorine so a pH of 8.0 is not that critical but can lead to scaling if your calcium is high.

The constant use of low pH products has a tendency to keep lowering the TA and pH so a higher TA tends to keep things in line longer. The same thing is seen in swimming pools that are chlorinated with trichlor tabs and to a lesser extent, dichlor granules. However, while running the TA high migh mean that sodium bicarbonate does not have to be added as often under these conditions and might mean that your pH MIGHT remain a bit more stable (or climb too high), IMHO, it is still easier to keep the TA lower and just keep tabs on your pH and TA through proper testing and adjust when necessary.

Ideally, once your water is balanced sanitizer and pH should be tested daily (maybe in a perfect world! ;) , try for at least 2-3 times a week!)

TA should be tested weekly and calcium hardness should be weekly or monthly depending on how hard or soft your fill water is. I would test it weekly until you know how much change, if any occurs as you add water to make up for evaporation and splashout. If your calcium levels tend to stay pretty much the same then I would just test it monthly.

There is NO reason to use your CYA test on a bromine system but if you ever convert to chlorine it might be useful if you use dichlor.

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Somebody probably thought that with such a small water volume in a spa that extra pH buffering would be a good thing, but they forgot that the pH buffering using sodium bicarbonate also has the side effect of wanting to increase pH. And yes, technically, your TA is too high

I think this is a hangover from way back when as in the late 70's when I was introduced to spas we were all told to use bromine tablets and to hold the TA in the 120 + range as the Bromine tablets were acidic.

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waterbear was right. I was thinking chlorine, not bromine. Sorry for the confusion. The principle of lower TA causing less pH rise still applies to a bromine pool, but if the bromine source is acidic, then your pH risks swinging more wildly. Since this particular hot tub is finding strong pH rise and not pH drop, the source of disinfectant must not be that acidic so lowering the TA is appropriate. The fact that the TA dropped so readily at lower pH (and with aeration) does seem to indicate that we may be on the right track here. Let's see if it works in this situation...I'm holding my breath and keeping my fingers crossed waiting for the final result...

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Ok well first off I made a incorrect assumption about sanitation. I thought that superoxidising with bromine was the same as doing a shock with chlorine.

I have not been shocking with MPS or chlorine at all.

What I have been doing is using Bromine concentrate regularly and a superoxy once a week with bromine.

What is MPS?

I have Chlorine shock left over from when I switched to bromine.

My test stats from 4:30pm today.

TA- 70PPM

PH - Between 7.6 and 8.0 It went up a bit.

CH 200PPM

If I'm using Bromine Concentrate as a sanitizer should I not use chlorine shock? MPS instead?

Also what the heck is superozadizing with bromine if it's not considered a shock?

I'm thinking the lower TA is helping because the ph did not go all the way to 8.0 since the last test.

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If you have just been adding more bromine to your spa, then you haven't been shocking it at all (just as you surmised). However, something called "superoxy" is likely to be more than just bromine -- it is probably either chlorine or a non-chlorine shock (oxidizer). Perhaps waterbear knows for sure or you can look at the label and let us know the ingredients.

MPS is Potassium Monopersulfate which is the most common type of non-chlorine shock. It sometimes goes by the trade name of Oxone, but is sold under many different brands. It is essentially just an oxidizer, just like chlorine and bromine, but is strong like chlorine so can be used to regenerate bromine.

In a bromine spa, the bromine is essentially in two forms. The active and disinfecting form is hypobromous acid (HOBr). When this gets used up by disinfecting a pathogen or oxidizing an organic (or ammonia), it gets converted to the other form which is bromide ion (Br-). This is very similar to how chlorine works, but the neat trick here is that the bromide ion can be regenerated back into hypobromous acid by adding a stronger oxidizer to your spa, such as chlorine or MPS in a process known as shocking. If you have chlorine shock left over, you can still use it to regenerate bromine (i.e. to shock your spa). Let us know what kind of chlorine shock you have -- does it say "dichlor" in the ingredients?

As for "what is superoxidizing with bromine", I don't know. It certainly sounds confusing. Maybe they meant that it "superoxidizes bromine" meaning it regenerates bromine by oxidizing bromide ion. Again, look at the ingredient label to see if it says either hypochlorous acid (or sodium hypochlorite or something with chlorine in it including Dichlor) or potassium monopersulfate (or something with "per" in it like perborate or peroxide).

It sounds like the pH rise has slowed down a bit and that is good. Perhaps we are on the right track after all. Once we get things sorted out a bit, we might consider adding borates (Borax) to your spa to act as another pH buffer so at least you won't need to add acid as frequently, but right now let's take one step at a time and figure out what this SuperOxy is.

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Ok my sanitizer is:

Spaguard Bromination Concentrate

active ingredients:

Sodium dichloro-s-triazinetrione 82.5%

Sodium bromide 14.7%

Other 2.8%

Ok here is what the bottle says on the back about the superoxidation:

A super ozidation dose is needed to destroy water soluble organic wastes. This may be needed on a daily basis in a heavily used spa, once a week in a moderately used spa. Add 4 teaspoons of this product per 200 gallons of water with circulation system operating.

So after reading that again I see that this has nothing to do with sanitizing but more so to get rid of organic wastes. Dow!!!!

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Ok well first off I made a incorrect assumption about sanitation. I thought that superoxidising with bromine was the same as doing a shock with chlorine.

Superoxidizing is the same a shocking. In a bromine system it serves two purposes. The first is to convert the bromide ions into the active hypobromous acid sanitizer. The second is to burn off organics, ammonia, and bromamines that form in the water. This second part is achieved by brining the free bromine levels above 10 ppm just like in 'shocking' a chlorine system with chlorine. The bromine levels are raised this high by adding enough oxizider (superoxidizing) to convert enough of the bromide ions into hypbromous acid (free bromine) so the level is above 10 ppm

I have not been shocking with MPS or chlorine at all.

If you have been adding any type of oxidizing agent (and it sounds like you are doing a 2-step bromine system) then you are most likely using either MPS or dichlor, they are the most commen oxidizers used with bromine systems. There is really no advantage in a bromine system to using MPS and it acutally has some disadvantages in my opinion such as it's low pH and the fact that it contributes to the TDS in the form of sulfates in the water. It is also more expensive (and a much bigger profit maker for the chem compaines and dealers!) It is usually marketed by the claim that it's use gives you a chlorine free system but this is hype (more like marketing BS than hype!). In a bromine system chlorine will get converted into bromine so even if you use a chlorine oxidizer you wil still have a chlorine free system as long as there is a bromide reserve in the water!

What I have been doing is using Bromine concentrate regularly and a superoxy once a week with bromine.

You mean you are adding sodium bromide regularly and an oxizider...most likely MPS to activate it. This is a 2-step bromine system. If your superoxy also contains bromine it is most likely a mixture of sodium bromide and either dichlor or MPS. Combination products like this are also on the market.

What is MPS?

Potassium Monopersulfate (it has a few other similar chemical names), a product developed by DuPont under the trade name of Oxone. They still market it under that name for pool and spa use. It is also used in denture cleaners, non chlorine bleaches, and many other household products. If you ever see 'non chlorine shock' for a pool or spa it is going to be MPS. (There are a very few other products that are also called non chlorine shock but their use is VERY rare and usually a speciality niche. Sodium Percarbonate is an example, It was once marketed to the commercial pool industry as a non chlorine shock but my understanding was it interferred too much with the automatic equipment used for chlorine dosing (ORP controllers) so I believe the only thing it is really used for now is to convert a biguanide (Bacqua, SoafSwim, Revacil) pool or spa into a chlorine one.

I have Chlorine shock left over from when I switched to bromine.

If it is dichlor, calcium hypochlorite, lithiuim hypochlorite, or sodium hypochlorite--liquid chlorine it is suitable for oxiziding a bromine system. They all have pros and cons but all can be used. I prefer the liquid myself in the form of laundry bleach.

My test stats from 4:30pm today.

TA- 70PPM

PH - Between 7.6 and 8.0 It went up a bit.

You are leaving out one very important piece of info that would affect the pH reading (but NOT the pH). What is your total bromine reading? High bromine readings (above 10 ppm) can cause interferance to the pH test causing it to read higher than it really is! I've spouted emough chemistyr in this post already so I will spare you the technical side (Chem_geek, be my guest! :D but suffice to say that you should always test your pH (and TA for that matter) when your sanitizer level is BELOW 10 ppm and never immediately after shocking or oxidizing!

CH 200PPM

If I'm using Bromine Concentrate as a sanitizer should I not use chlorine shock? MPS instead?

If you bromine concentrate is plain sodium bromide it really doesn't matter, I prefer laundry bleach because of the ease of dosing (about a cup per 250 gallons), availability, stability (you KNOW how long a jug of laundry bleach stays good for!), and price. You can also effectively use dichlor, calcium hypochorite, lithium hypochlorite (expen$ive stuff), or MP$( also expen$ive and not my first choice.)

Also what the heck is superozadizing with bromine if it's not considered a shock?

Shocking and superoxizing are the same. One thing that people need to realize is that 'shock' is a verb, not a noun! (it is something we do to a hot tub or pool by adding a large amount of oxizider--superoxidizing, if you wil. It is NOT a product that we add even if the product is called Shock....this is just more marketing BS!)

I'm thinking the lower TA is helping because the ph did not go all the way to 8.0 since the last test.

It very possilby did but you need to figure into it the last factor that I mentioned. Make sure your total bromine readings are below 10 ppm wihenever you test your pH and TA!

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Ok my sanitizer is:

Spaguard Bromination Concentrate

active ingredients:

Sodium dichloro-s-triazinetrione 82.5%

This is dichlor...a form of stabilized chlorine!

Sodium bromide 14.7%

This is the source of bromide ions that get oxizided into hypobromous acid by the clorine

Other 2.8%

This is actually a 2 step bromine system combined into one product.

Ok here is what the bottle says on the back about the superoxidation:

A super ozidation dose is needed to destroy water soluble organic wastes. This may be needed on a daily basis in a heavily used spa, once a week in a moderately used spa. Add 4 teaspoons of this product per 200 gallons of water with circulation system operating.

So after reading that again I see that this has nothing to do with sanitizing but more so to get rid of organic wastes. Dow!!!!

This is what we call shocking the tub! If there is enough bromide ions in the water(there will be after using the aove product for a few weeks!) you can achieve the same thing by adding a cup of laundry bleach for every 250 gallons or a tablespoon of dichlor for every 250 gallons. You should find that your total bromine levels rise above 10 ppm when you do so.

Hope this helps!

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Can I use any type of laundry bleach ?

My spa is 325 gallons.

It seems weird to use laundry bleach just because I never heard of it being use that way. If I do this it might take some time getting used to the idea.

It just seems wrong. But don't get me wrong I buy into this, it's just the idea of it. lol !!

So can I brighten my brites with dichior? lol!!

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Excellent news, and your most welcome. All that really matters is that you got your problem solved. It looks like the "lower your TA" advice to help slow down the rise in pH has worked again. Though this helps to validate the cause being the outgassing of carbon dioxide, helping you out is even more gratifying. Happy holidays to you and everyone (waterbear, too).

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