Troubles With Ta And Ph

[astewart]

Hi guys. It’s been a pleasure reading your stuff on spa water chemistry. Thanks for doing this. I think it’s helping . . . but I still have a question or two.

First of all, the (Taylor) numbers:

Tub Beachcomber 720 litre

Tub use One person, occasional

Sanitizer Dichlor until CYA 40 then bleach.

FC I keep it between 3 and 5 ppm, shock to 12 occasionally

PH Usually high. Now at 7.7

TA 40

CH 250 (half well water and half softened water)

CYA 40 (measured by test strips)

Borate 25 PPM (added 30 gm Beachcomber ‘Soft’ and estimate < 25 PPM)

Water clear and odourless

I’m having trouble with TA and pH. (What else is new?) I know that they’re related somehow but I can’t figure out how. I’ve been trying to drive TA down from 180 to an acceptable level hoping that pH would follow. I finally got it to 60 PPM using dry acid but pH was still at 8.2 (measured using a Taylor kit and a pH meter). Earlier notes from Nitro and others suggest that one should continue to drive down pH and let TA settle where it will so I carried on down.

But first, I added 30 gm Beachcomber ‘Soft” hoping that a very small addition of borate would help settle pH movement as TA decreased. This may have been a mistake. PH went back up to 8.4.

I then added more acid using The Pool Calculator as a guide for quantities. TA is now 40 with pH at 7.7. Altogether I have added 325 gm acid.

The Pool Calculator says I’m now out of balance, with TA well out of range low and pH creeping back up. My question is, what now? I’d appreciate any help you can offer.

Alan

[chem geek]

Alan,

I looked at Beachcomber products here and all it says about "Soft" is the following.

Soft

A granular product that enhances bather comfort, reduces calcium buildup and protects against pH bounce. Soft promotes a more stable, balanced water environment and ‘softens’ water to the touch for a more pleasing hot tub soak.

Are there ingredients listed on the bottle? If it reduces calcium buildup, then this might be a phosphate buffer and not borates. It also sounds like it wasn't necessarily pH balanced since the pH apparently rose upon addition. A phosphate buffer can precipitate calcium phosphate, thus reducing CH and temporarily clouding the water.

I would get the borates level up to 50 ppm, possibly higher since your spa is small, but I'd first see what is in the Beachcomber Soft product first. You might have to dump the water and start over if the "Soft" product isn't really borates (either boric acid or sodium tetraborate pentahydrate or some combination).

It sounds like you don't have the Taylor K-2006 otherwise you would have been able to measure the CYA via a turbidimetric test rater than by test strips. CYA via test strips are notoriously inaccurate. In your case, however, keeping track of how much Dichlor you added will give you a very good idea of the CYA level since every 10 ppm FC cumulatively added increases CYA by 9 ppm. What model of Taylor test kit do you have that doesn't have a CYA test with it?

I would leave the TA at 40 ppm and not go lower, at least not right now. Also, don't fight the pH trying to get it below 7.7 as it might be more stable there and there is nothing wrong with that pH. With at least 50 ppm Borates, I suspect the pH will be reasonably stable at 7.7 with a TA of 40 ppm. Your tub is somewhat small at 190 gallons so swings in water chemistry and pH will be more common since you still put out the same amount of bather waste that needs to get oxidized by chlorine, but the amount of bleach to do that (roughly 5 fluid ounces per person-hour of sodaking) will have the pH swing high upon addition.

Does your tub have an ozonator? The aeration jets in a small volume of water will tend to outgas carbon dioxide very effectively and is probably the primary cause of your pH rise. Also, are you using 6% Clorox Regular for bleach? If you are using an off-brand Ultra bleach, it is higher in "excess lye" and that will tend to make the pH rise over time, though not as quickly as you are seeing.

Richard

[quantumchromodynamics]

I think that "Soft" is probably a phosphate pH buffer.

You can get some borate test strips to determine if you have any borates in the water. You can also test for phosphates, but I'm not sure what levels you could expect if "Soft" is a phosphate pH buffer. I would think that the levels would be too high for the normal phosphate test to work.

On your next fill, use more water softener to keep the calcium level below 150 ppm.

I would recommend muriatic acid for pH and alkalinity reductions in the future. I think that it works better. Get a quart instead of the gallon for easier handling. Open the bottle outside and pour the necessary amount into a disposable plastic cup (not paper or Styrofoam) and then bring the cup inside and pour the acid into the hot tub.

Using thepoolcalculator, I get a CSI of -0.3 for your CSI. I think that anywhere in the -0.3 to 0.0 range is fine. The CSI is more important than the alkalinity. As long as the pH remains stable at the desired level, your alkalinity is fine.

With your high calcium, you are at increased risk of scaling, so keeping the CSI at the lower end of the range will be better for you. If you target-0.3 to -0.2, that will give you some margin of safety if your pH rises for a short period.

If you do decide to add boric acid/borates, I recommend that you use boric acid instead of Borax. Most of the boric acid <> borate equilibrium will be boric acid so adding the boric acid/borates as boric acid will be more pH neutral.

[astewart]

Thanks for the reply, Richard . . . and also for the reminder to think a bit before I add unknown chemicals to my tub that I can't get back out. I had read two notes on the Trouble Free Pool forum that Beachcomber "Soft" was a likely pH buffered borate product. It seems that may not be the case. I notice that, after replying to me, you replied also to the folks on TFP with the comment that "Soft" may be something other than borates. The bottle says nothing about what Soft contains.

I have not used the tub since my first post and your reply. Testing now (with a Taylor K-1004 kit) shows TA at 40, pH at 8.0. My local Beachcomber people tell me that my CA is 160. I have no way of knowing whether that or the earlier 250 number is correct. They don't test for CYA so my 30/40 from test strips is all I have to go on.

The bleach I'm using is Ultra Javex Original by Chlorox. There's no mention on the bottle of its concentration. I have no ozonator and most jets and aerators are turned to low or off.

The Pool Calculator tells me that I'm again out of balance and that raising TA to between 50 and 100 with pH at 8.0 would be balanced. Unfortunately, 8.0 pH is too high for comfortable tub use. An alternative is dropping pH to 7.7 while raising TA to between 60 and 110. That would also be balanced. My dilemma is that I need TA and pH to go in opposite directions and don't know how to do that.

Thank you for any suggestions you may have.

Alan

By the way, I have a box of borax and could add some. I presume that 720 liters is 720,000 ml which is 720,000 gm which I could then use to work out how many grams of borax is needed to get to 50 ppm. Cat it be as simple as that?

[quantumchromodynamics]

The 50 ppm is calculated as 50 ppm of boron. Borax is Sodium Tetraborate Decahydrate. You have to calculate the percentage of boron in the Borax to determine how much to add.

10.811 X 4 /381.37 = 0.1134. 50/0.1134 = 441 grams per 1,000 liters.

441 X .720 = 317 grams.

You can use thepoolcalculator to calculate the correct amount of Borax or boric acid to add.

I recommend Boric acid because it is easier to use and it is more pH neutral. Borax requires the addition of muriatic acid to compensate for the pH and Alkalinity that will be caused by the addition of the Borax.

Your tub would require 206 grams of boric acid to achieve 50 ppm.

thepoolcalculator shows how much acid to add before adding the Borax to compensate for the pH and Alkalinity rise that is caused by adding that much Borax.

317 grams of Borax will require 158 milliliters of muriatic acid to compensate for the pH rise.

You determine the correct TA by watching your pH level. If the pH is constantly too low, then your TA is too low. If the pH is constantly too high, then your TA is too high. If the pH is constantly good, then your TA is good. If your TA needs to be at 30 to maintain a good pH, then that is OK.

[quantumchromodynamics]

I think that you should get a new test kit. You need to know your calcium and cyanuric acid levels. I also think that your readings for pH and alkalinity may be inaccurate.

[astewart]

Thank you for your help with my TA/pH problem. I've read your responses and was happy to read yesterday that TA below 40 is acceptable if that's where it needs to be.

I think you're right about my test kit. I tried to order the proper K-2006 kit from two suppliers in the US but neither would ship it to Canada. I'm pretty sure my readings are accurate. I've done them very carefully many times and they always agree fairly closely. They agree also with tests done by my Beachcomber tub guy. This evening they are: TA 40 using the Taylor kit and pH at 8.0 using Taylor and an Oakton Instruments Ecotestr-pH2 electronic pH tester. The water is crystal clear and odourless.

To be absolutely certain about this I'll take a sample with me tomorrow to a different spa supplier and have a full test done. I'd like to find out for sure about my CYA levels. If my TA and/or pH measure differently I'll know I'm having testing troubles as you suggest. And, I'll continue looking for a full Taylor kit here in Canada.

Thanks again for your help.

Alan

[cofive]

I've been watching this thread and now have questions. I think I understand the coorelation between TA and Ph and how when you've adjusted the TA to a point that Ph is stable that we could call that the 'ideal' TA level. But I'm wondering is it at all possible to actually adjust both to say a 100 TA and a 7.5 Ph? And how would one do that? Is there really a way to raise TA and lower Ph or vise-versa, just to get numbers?

Ken

[quantumchromodynamics]

I've been watching this thread and now have questions. I think I understand the coorelation between TA and Ph and how when you've adjusted the TA to a point that Ph is stable that we could call that the 'ideal' TA level. But I'm wondering is it at all possible to actually adjust both to say a 100 TA and a 7.5 Ph? And how would one do that? Is there really a way to raise TA and lower Ph or vise-versa, just to get numbers?

Ken

You could get the pH and alkalinity to those numbers. However, the numbers would not last very long. The pH would begin to rise immediately and it would be a waste of time.

[chem geek]

I've been watching this thread and now have questions. I think I understand the coorelation between TA and Ph and how when you've adjusted the TA to a point that Ph is stable that we could call that the 'ideal' TA level. But I'm wondering is it at all possible to actually adjust both to say a 100 TA and a 7.5 Ph? And how would one do that? Is there really a way to raise TA and lower Ph or vise-versa, just to get numbers?

As QCD noted, you can adjust the pH and TA to whatever level you want, but it won't be very stable. To make the pH not rise as quickly in spite of a higher TA, you could shut off all aeration of the water, including circulation, and cover the tub. That will prevent the carbon dioxide outgassing and make the pH more stable, but at the cost of 1) not being able to use the tub nor the jets and 2) having possible problems with the water due to a lack of circulation.

My own pool tends to have the TA rise over time due to some evaporation and refill as my fill water has 80 ppm TA, so the TA in my pool tends to run around 110-130 ppm. However, the pH in my pool is very stable because it is mostly covered most of the time with an electric mostly opaque safety cover. This significantly cuts down the amount of carbon dioxide outgassing that causes the pH to rise. If I had an uncovered pool, I'd probably need the TA to be no higher than 80 ppm to get reasonable pH stability. Note also that a pool doesn't have aerating jets the way a spa does and that pool circulation is rather mild compared to the fairly rapid circulation and churning of water in a spa.

Adding 50 ppm Borates helps with pH stability, but only lowering the TA cuts down the true source of rising pH. Doing both, is a one-two punch to get fairly stable pH while still being able to use the spa the way you like it with aerating spa jets.