Low Ph Hi Ta - How To Raise Ph And Lower Ta?

[OttawaGreg]

My Ph was 6.5 and TA 141. I dumped in a full cap (30 grams) of Ph-UP and the next day it read Ph 7.0 TA 165.

The good news is less foam with the jets on high. I know, my TDS is probably up there now but I'm stretching it before our next water change.

The bad news is TA goes up with Ph.

I leave my air on full at all times to try to lower TA.

I don't want to add Lo-N-slow as it will take my Ph down along with the TA.

I've read about Muriatic Acid but don't know what it is or where to get it.

Any suggestions?

thanks,

Greg

[shovelhd]

I've read about Muriatic Acid but don't know what it is or where to get it.

Any suggestions?

thanks,

Greg

You can get it in a gallon jug at any decent hardware store, i.e. Ace, True Value, etc. It costs a couple bucks. IMO it does a better job than dry acid, just be very careful handling it.

[OttawaGreg]

thanks for that. Easy then, a trip to True Value it is...

[Nitro]

To raise pH without raising TA, you can turn on all the jets/air and let run for 30 mins. Read my link below about Lowering TA.

[OttawaGreg]

To raise pH without raising TA, you can turn on all the jets/air and let run for 30 mins. Read my link below about Lowering TA.

You know, I do that most evenings by just using the tub. Say 1 hour each night with the air full and jets on high and it's never (noticeably) raised the pH. I keep a spa log of readings and it's always the same thing, pH is too low and TA is too high. I can fix either one but the other then goes out of wack.

pH-Up or ALC-up will raise both (pH & TA)

Lo-N-Slo will lower both (pH & TA)

I am starting to think pH is MORE important then TA as when my pH is in range the water behaves better, less odor and less foam.

What about baking soda? is it any different?

thanks for your suggestions, btw I have read (and re-read) your link and refer to it often.

Greg

[Nitro]

You know, I do that most evenings by just using the tub. Say 1 hour each night with the air full and jets on high and it's never (noticeably) raised the pH. I keep a spa log of readings and it's always the same thing, pH is too low and TA is too high. I can fix either one but the other then goes out of wack.

pH-Up or ALC-up will raise both (pH & TA)

Lo-N-Slo will lower both (pH & TA)

I am starting to think pH is MORE important then TA as when my pH is in range the water behaves better, less odor and less foam.

What about baking soda? is it any different?

thanks for your suggestions, btw I have read (and re-read) your link and refer to it often.

Greg

There is no particular correct range for TA, so don't bother trying to get it there. Your TA should be at WHATEVER level it needs to be to keep pH in range (7.6-7.8). That means if you pH is low, you need to raise TA (with baking soda) to keep pH higher. If pH is too high (the norm), you need to lower TA (with acid) to keep pH lower. And if pH is stable, don't touch TA.

Bottom line, adjust TA (with baking soda and/or acid) so that pH is stable between 7.6-7.8.

[PaulR]

These are the pH/TA treatments I'm aware of:

Baking soda = sodium bicarbonate, raises TA without much effect on pH.

Soda ash = sodium carbonate, raises both pH and TA.

Borax (as in 20 Mule Team) raises pH without much effect on TA.

Acid (muriatic or dry) lowers pH and TA.

Aeration raises pH with zero effect on TA.

(Soda Ash sometimes available as Arm & Hammer Washing Soda, not the detergent so be careful!)

--paulr

[OttawaGreg]

These are the pH/TA treatments I'm aware of:

Baking soda = sodium bicarbonate, raises TA without much effect on pH.

Soda ash = sodium carbonate, raises both pH and TA.

Borax (as in 20 Mule Team) raises pH without much effect on TA.

Acid (muriatic or dry) lowers pH and TA.

Aeration raises pH with zero effect on TA.

(Soda Ash sometimes available as Arm & Hammer Washing Soda, not the detergent so be careful!)

--paulr

thanks for the information. I am interested in trying Borax but do not think we have the 20 Mule product here in Canada. Does anyone have an idea where to get it and in what form/product? I am guessing this may be something I'll find at Home Depot, Reno Depot, Canadian Tire?

thanks,

Greg

BTW I just dumped in 30+ grams of pH-UP and brought the pH from 6.6 to 7.5, perfect. TA went from 131 to 164 though.

[chem geek]

You don't see any of this in Canada? You should be able to find it at WalMart, at the local No Frills grocery store, Food Basics grocery, etc. It will likely be in the laundry aisle.

If you use it for raising pH, it will only raise the TA by half as much as pH Up.

[OttawaGreg]

AN UPDATE:

I used muriatic acid to lower both TA & pH instead of Lo N Slo. It did the trick. TA = 110 pH=6.2

Next I slowly use Borax to raise the pH. 30g takes it from ph=6.2 to 6.4. TA=119

Next day 60g Borax and pH=6.7 TA=122

I will keep using Borax to raise the pH as it appears to have little to no effect on TA.

Now, I know my water is 3 months old and probably the TDS is quite high as we use it allot, but there is a slightly different odor now. A chemical sort of odor that I can feel in my eyes a bit. The Chlorine has been steady around 2.2 -> 3.3. The water is clear but foams a bit with the jets on high.

Is anybody else using Borax and finds it gives an odor? I made sure it was simple Borax and there was no detergent, scent, phosphates etc. in it.

thanks for the suggestions,

Greg

[quantumchromodynamics]

What test kit do you have?

What type of chlorine are you using?

Can you give a list of all chemicals that you use?

[OttawaGreg]

I use ;

AQUACHEK TRUTEST DIGITAL TEST STRIP READER

Which is just a digital reading of a test strip.

Spaguard chlorine concentrate as a sanitizer and the other Spaguard chemicals for balancing. I just recently used muriac acid and Borax to balance instead of the Spaguard products and noticed a change in odor. It's not that strong an odor, but noticeable.

[chem geek]

Having a Calcium Hardness (CH) of 100-120 ppm or so would reduce foaming, but since you are using test strips you will be unable to measure CH since test strips can only measure Total Hardness (which includes magnesium). Also, test strips are not very accurate for many of the tests.

It is true that using Borax instead of pH Up has the TA rise about half as much for the same pH rise. It does have an effect on TA, just half as much. To raise the pH with no change in TA, aerate the water.

Since you seem to be having low pH a lot in spite of a higher TA that either means your test numbers are wrong (due to the test strips) or you are using acidic sources of oxidizer. Are you using Dichlor or non-chlorine shock (MPS)?

See this post. Your problem is most likely due to the very high Cyanuric Acid (CYA) level built up from continued use of Dichlor and heavy tub use. Using the Dichlor-then-bleach method would avoid this problem (see the link in the other post).

[quantumchromodynamics]

Having a low pH and a high alkalinity is unusual unless the alkalinity is composed of a lot of non-carbonate or non-bicarbonate and you are adding acidic chemicals, such as trichlor. Carbonates and bicarbonates protect from pH drop more than pH rise and the pH rises from loss of carbon dioxide during aeration.

Non-carbonate alkalinity from boric acid, phosphoric acid, cyanuric acid (C₃H₃N₃O₃) or dimethylhydantoin (C₅H₈N₂O₂) protect mostly from pH rise and do not outgas due to aeration.

Actually, the acids do not contribute to the total alkalinity. The acids are in equilibrium with their conjugate bases. It is the bases that contribute to total alkalinity. Total alkalinity only measures resistance to pH drop, not rise. The acids contribute to total acidity which measures resistance to pH rise. I think it would be useful for test kits to include a test for total acidity.

Can you provide a full set of chemical readings including calcium and cyanuric acid?

It is important that you have a test kit that can test for

Free chlorine

Combined chlorine

pH

Total alkalinity

Calcium hardness (Not total hardness)

Cyanuric acid.

Boron (If using borax or boric acid)

Phosphates (If using phosphate based pH stabilizers)

Dimethylhydantoin comes from bromine tabs, if you are using any of those, and may show up on the cyanuric acid test, but I'm not sure. Cyanuric acid comes from dichlor granules or trichlor tabs or granules.

[chem geek]

According to this post, Greg is using a combination of lithium hypochlorite and Trichlor tabs. That explains the low pH (from the Trichlor) and probably the poor water quality (from high CYA from the Trichlor).

FYI, DMH from bromine tabs will not show up in any of the standard tests -- it does not show up in the CYA test as that test uses melamine to form a very specific precipitate of melamine cyanurate (at low pH to force more precipitate).

[quantumchromodynamics]

...it does not show up in the CYA test as that test uses melamine to form a very specific precipitate of melamine cyanurate (at low pH to force more precipitate).

The name melamine cyanurate is somewhat misleading. High pH would form more cyanurate. Low pH forms more cyanuric acid. I think that it's clearer to use the term melamine cyanuric acid complex because the product is melamine and cyanuric acid.

(C₃H₆N₆•C₃H₃N₃O₃)

Do you know how much dimethylhydantoin contributes to total alkalinity?

[OttawaGreg]

According to this post, Greg is using a combination of lithium hypochlorite and Trichlor tabs. That explains the low pH (from the Trichlor) and probably the poor water quality (from high CYA from the Trichlor).

FYI, DMH from bromine tabs will not show up in any of the standard tests -- it does not show up in the CYA test as that test uses melamine to form a very specific precipitate of melamine cyanurate (at low pH to force more precipitate).

Richard,

Yes, the low pH problem was solved thanks to all your help. It is certainly my sanitizers.

The main point of this thread was figuring out how best to raise the pH and not the TA. The Muriac acid does the trick. It's been a few days now and the TA has stabilized. I am slowly adding Borax and seeing the pH raise (slightly) while TA pop a bit then go back down. Just what I wanted.

Greg

[chem geek]

I agree with you that the alternate names of "melamine-cyanuric acid adduct" or "melamine-cyanuric acid complex" or "melamine-cyanuric acid compound" are more descriptive, though "melamine cyanurate" is probably the most commonly used even though it is technically inaccurate. The actual complex itself is indeed formed between cyanuric acid (not one of the cyanurate ions) and melamine. You can see the chemical structure in the Wikipedia article here.

I do not believe that dimthylhydantoin is acidic so it probably does not contribute at all to Total Alkalinity (TA).

I'm sure there is some sort of equilibrium between chlorine and DMH just as there is between chlorine (hypochlorous acid) and Cyanuric Acid or glycoluril, but I can't find any literature on that. It's somewhat of a moot point since DMH is used in brominating tablets so chlorine would get used up oxidizing bromide to bromine anyway and having some bound temporarily is not a big deal (it just slows down such conversion reactions due to lower hypochlorous acid concentration). DMH obviously does bind to both bromine (as in DBDMH) and chlorine (as in BCDMH and DCDMH) but I can't find equilibrium constants for such binding so don't know how much of a moderating effect DMH has on bromine. I suspect it is minimal for the same reasons that CYA doesn't significantly moderate bromine's strength (and is the basis for sodium bromide algicides which work around high CYA levels by producing bromine).

[quantumchromodynamics]

I do not believe that dimethylhydantoin is acidic so it probably does not contribute at all to Total Alkalinity (TA).

It seems to me, from the formula, that dimethylhydantoin (C₅H₈N₂O₂) is a weak acid, based on all of the hydrogen ions, and that it would dissociate into its available bases until it reached equilibrium, in the same way that cyanuric acid does, by giving up one or more hydrogen ions. The bases would then be able to accept hydrogen ions from introduced acid. Do you think that this is not correct?

[chem geek]

The hydrogens attached to the carbons aren't going to get unbonded. It's only the two hydrogens attached to the two nitrogens that have a prayer of dissociating from the main molecule in a way similar to CYA. It is these sites where the bromine or chlorine are attached in the standard bromine products (BCDMH, DBDMH).

I'm having a hard time finding the pH of DMH in solution which would help answer your question. I did find this link that describes how one of the two halogens on DMH gets hydrolyzed within an hour while the second one takes quite a bit longer, perhaps days. Of course, this is probably at 77F and at spa temperatures I suspect the reactions are far faster. The tablets are intentionally compressed to dissolve more slowly (similar to Trichlor). This link gives a pH of 3.5 at 0.15% diluted solution, but keep in mind that a low pH is expected due to the reaction that creates hypobromous and hypochlorous acids:

DMH+Cl+Br + 2H₂O ---> DMH+H+H + HOCl + HOBr

HOCl ---> H⁺ + OCl^-

HOBr ---> H⁺ + OBr^-

Though the hypobromous acid doesn't dissociate much at a pH of spas at 7.5, in distilled water, which is how the pH tests are measured, such dissociation occurs. For comparison, Trichlor gives a pH of 3.0 to 3.5 for a 1% solution.

So it does roughly seem like maybe DMH dissociates one of its hydrogen atoms, but it's not clear if this starts happening above or below a pH of 7.5. So I can't tell you if it affects the TA reading.

[quantumchromodynamics]

This link says that the molecule can donate two hydrogen ions or accept 4 hydrogen ions.

dimethylhydantoin (C₅H₈N₂O₂)

[Nitro]

HUH?

[Nitro]

LOL!

[chem geek]

(by the way, the chemical structure you showed was for DCDMH, that is the dichloro version since you show chlorine attached to the nitrogen instead of hydrogen).

Yes, but at what pH? That is, what is the pKa for the dissociations (especially the first one)? If you can find that, then that would help answer the question. As for accepting protons, that probably only happens at extremely low pH. I could try modeling what the dissociation constant would be based on the resulting 3.5 pH number in distilled water for a 0.15% solution of BCDMH but it would be far easier if we could find an MSDS or something indicating the pH of a solution of DMH by itself or the pKa number directly. I would think it's been determined and is published somewhere.

Anyway, I presume you are asking because a buildup of DMH over time in spas using brominating tablets would replace the carbonate buffer with a DMH one and would affect any saturation index calculations (very similar to increasing CYA from Dichlor or Trichlor). So let's brute-force figure this out. I found this link for DCDMH that says that a 0.1% aqueous solution has a pH of 2.97 and since I already have a spreadsheet model for chlorine (including ionic strength), it's easiest to use that with some modifications. I can just use Dichlor as a starting point and disable the CYA dissociations and then adjust the first constant until I get the desired pH.

First, as a reference, a saturated solution of Cyanuric Acid in water according to this MSDS and other sources is 0.3g/100ml and has a pH of 3.8-4.0. Based on the pKa for CYA (6.88, 11.4 and 13.5), my spreadsheet gives a result of a pH of 4.26. Let's work this out manually to make sure there is no error here. Only the first dissociation will be relevant (the amounts for the second and third dissociations will be exceedingly small).

CY-H₃ <---> CY-H₂^- + H⁺ pKa = 6.88

[CY-H₂^-]*[H⁺]/[CY-H₃] = 10^-6.88

[CY-H₂^-] = [H⁺] for practical purposes (initial H⁺ is much smaller than final)

CY-H₃ = Initial-CYA - CY-H₂^- and is approximately just Initial-CYA since very little dissociates.

Initial-CYA = 0.3g/100ml = 3g/1000ml = 3g/liter = (3 g/liter)/(129.07 g/mole) = 0.0232 moles/liter

so

[H⁺]² = 10^-6.88 * 0.0232

[H⁺] = 5.53x10^-5

pH = -log¹⁰(5.53x10^-5) = 4.26

One can go back and verify the assumptions or approximations I made and see that they are valid so the spreadsheet calculation is correct (it even accounts for ionic strength, though that isn't a big factor here). So we need to be a little careful directly comparing against some of these MSDS values.

So let's look at our equivalent to DCDMH, using 2/3rds the molar amount of Trichlor (since DCDMH has 2 chlorine while Trichlor has 3), and initially have no dissociation for CYA.

0.1% = 1000*(0.1/100) g / liter = 1 g/liter = (1 g/liter)/(197.04 g/mole DCDMH) = 0.00508 moles/liter = (2/3)*(0.00508 moles/liter)*(232.41 g/mole Trichlor) = 0.786 g Trichlor

My spreadsheet gives a pH of 4.77 (disabling CYA dissociation and chlorine/CYA binding). Since the MSDS for DCDMH says the pH is closer to 3, this does imply that DMH is indeed acidic. If I now use the above Trichlor amount plus half that amount as added CYA to simulate DCDMH more accurately, then to get to a pH of 3 I get an implied pKa for DMH of 3.8 implying that DMH is indeed very acidic (though still technically a "weak" acid) and at spa pH of 7.5 would both lower pH and ultimately contribute towards TA if the pH were adjusted by addition of a base.

Let's assume that at spa pH the first dissociation is complete but that the second doesn't occur (if it does, then the alkalinity impact would be doubled). If the bromine usage were similar to chlorine usage, then this is typically around 4 ppm FC per day in 350 gallons for around 30 person-minutes of soaking. In one month, this is 120 ppm FC cumulative which in TA units is equivalent to 120*(100.087 g/mole CaCO₃)/(70.906 g/mole Cl₂)/(2 for double alkalinity effect from CaCO₃) = 84.7 ppm TA. That is very significant and would be double this amount if the second dissociation constant pKa(2) for DMH were significantly below 7.5. Of course, this assumes that all of the bromine is coming from the tablets while in reality there is also usually weekly shocking which takes care of some of the bromine demand.

Technically speaking, the addition of DMH doesn't change the TA. It just lowers the pH. Whatever TA is increased by the additional DMH^- ion is offset by the lower pH (i.e. increase in H⁺ ion). Now in practice, one would need to balance the pH so if this happens via carbon dioxide outgassing, then the pH would rise back up and the net effect would be no change in TA, though the carbonate portion of alkalinity would be decreased, offset by the increase in the DMH portion of alkalinity. If instead one added pH Up (Spa Up), then this would restore the pH back up but would also increase measured TA.

For you bromine users out there with brominating tablets in floating feeders, let us know if you see a drop in pH over time when using brominating tablets. If so, do you adjust for this using pH Up (Spa Up)? I've noticed that some brominating tablets include sodium carbonate to possibly balance the pH, but most do not.

Richard

[quantumchromodynamics]

Yes, I was aware that I was showing the chemical structure for DCDMH. I should have been more careful to label the structure properly.

And, yes, I was asking because the original poster specified high alkalinity and low pH. I thought that this could be a result of trichlor or possibly bromine tabs. I was wondering if the bromine tabs would have a similar effect to trichlor in lowering the pH and adding a compound that would affect the total alkalinity.

I think that being able to accurately determine the various components of alkalinity can help us better diagnose water conditions including accurate Saturation index calculations.

Here is a reference with some good information.

Here is an interesting reference from the Argonne National Laboratory called "The mechanism of the formation of hydantoins"

This reference contains this:

The hydrolysis of DBDMH was often assumed to be the in situ formation of hypobromites and the dimethylhydantoin, as shown in the Eq. (1):

DBDMH + 2H2O <> 2HBrO + DMH

Based on the above phenomenon, the hydrolysis process could be more complicated than this assumption. According to Eq. (1), it is difficult to explain the decrease in pH in the hydrolysis process, as the products HBrO and DMH are only very weak acids. However, it is possible that hypobromic acid could undergo further decomposition to form Br2 and strong acid HBrO3:

5HBrO <> HBrO3 + Br2 + 2H2O

The bromine produced in the above equation could also undergo a further disproportionation reaction to yield hydrobromic acid and hypobromic acid, as shown in Eq. (3):

Br2 + H2O <> H+ + Br- + HBrO

This reaction is very unfavorable to the forward direction as the equilibrium constant of this reaction is only 6.1 × 10^-9 (25°C). It is clear, however, that the further decomposition of hypobromic acid should be responsible for the increase of acidity and the change in the CL intensity when reacting with luminol. These hydrolysis reactions also imply that, apart from the DBDMH, more active species may exist in the sample solution.

I'm not sure why they are using the term hypobromic acid instead of hypobromous acid. It is from a Chinese or Japanese writer, so that could be the reason.