Raise Alkalinity when pH is high

[WiseOne]

Apologies if this has been asked before. I couldn't find it. I've seen how to lower TA, but this is the opposite.

215 gallon spa using 3-step Bromine sanitation and Frog mineral stick. Br 1.2 pH 8.3 TA 45 Ca Hardness 170 Borate 50

I'm guessing I need to overly increase TA and then lower pH. Questions are:

Best to use washing soda or baking soda to raise TA? I'll use dry acid to lower pH. 

How far over to? 

I've found the tub "feels" balanced and stays that way with TA around 80-100 and pH around 7.8. 

Thanks.

[waterbear]

How are you testing your Bromine? If you are using DPD or strips it is very possible that your sanitizer is actually high and your test is bleaching out? When sanitizer, either chlorine or bromine, is high it can cause the pH indicator to convert from phenol red to either chorophenol red or bromphenol red, which has the same color changes as phenol red except at a much lower pH range and if you are getting a reading of 8.3 and the indicator has converted all yo really know is that the pH is above 6.7.

Your bromine reading of 1.2 indicated that you are either using some type of  meter to test or you are using a Taylor FAS-DPD test kit with a 25 ML sample. If you are using the Taylor kit use a 10 ML sample which will give you a resolution of .5 ppm instead of the .2 ppm that the 25 ML sample gives. .5 ppm is all the resolution you need for testing sanitizer. IF you are using FAS-DPD then your pH is high and you should lower it. Procedure is at end of post.

If your TA is low you would use baking soda to raise it since it will raise TA with a minimal effect on pH. NEVER use washing soda unless you need to raise pH and TA. Washing soda is usually only necessary for swimming pools using trichlor, which is very acidic.

A TA of 45 is not out of line for a tub, where the recommended range is 50-70 for best pH stability., Read this:

https://www.poolspaforum.com/forum/index.php?/topic/52522-some-truths-about-ph-and-ta/

If you do want to raise the TA I would not go higher than about 70 ppm. Here is what to do:

1. Assuming your are using FAS-DPD testing for sanitizer first use an acid demand test to determine how much acid is needed to lower pH to desired level. I would suggest 7.6 to 7.7 if you are using borate.

2. Once pH is at target test TA and determine how much is needed to raise TA to target value. Test 24 to 48 houirs later and then test pH again.

3. lower pH to desired level using the acid demand test once again since baking soda (sodium bicarbonate) will cause a slight pH rise.

If you lower the pH a bit lower than your target don't worry, it will rise on it's own.

Final ardvise, ditch the Frog and raise your bromine to 4-6 ppm. since you are already using 3 step bromine.

17 hours ago, WiseOne said:

I've found the tub "feels" balanced and stays that way with TA around 80-100 and pH around 7.8. 

Feels balanced? Not sure what you mean. A tub is balanced when all the chemical parameters are where they are supposed to be. It does not have any effect on the 'feel' of the water unless the pH is way out of line or the CH is extremely high.

[WiseOne]

Thank you, Waterbear. I appreciate your precision. 

I had the water tested at a pool store with computerized readouts and verified my reading of test strips. With the Frog, Br can be as low as 1, so I'm happy with that, at least for now. My comment that it "feels balanced" was more of an intuitive sense based on water clarity, pH stability, lack of foaming and odor. 

I followed your suggestion of lowering pH and then raising TA. Things are much closer now. 

I wonder if you could put up a sticky with simple instructions of which chemicals and processes to use to routinely raise/lower pH and alkalinity. I thought I had read here previously that washing soda was good for raising pH with minimal effect on TA, whereas baking soda would raise TA with little effect on pH; and that aeration was an effective way to raise pH. You suggest here that washing soda is not useful for hot tubs. I'd actually enjoy understanding the (basic) chemistry of each addition.

The other sticky I'd love to see would describe the actual chemistry for a bromine tub. What happens to the sodium bromide with addition of oxidizer (Cl or O3 or non-chlorine shock); does the bromine dissipate with use or convert back to NaBr; what is the effect of sunlight on the bromine reserve and active bromine; etc. 

Thanks again. 

 

[waterbear]

15 hours ago, WiseOne said:

I had the water tested at a pool store with computerized readouts and verified my reading of test strips.

Invest in a Taylor Technologies K-2106 test kit. Strips are basically useless for several reasons, first and formoat that they do not have the precision required to properly balanced water. Computerized readouts do not mean a thing and they are designed to sell you products (I have previously worked in the retail end of the business and had been certified by LaMotte in their computerized testing system but also used Taylor liquid reagent testing which, IMHO, is far superior.

15 hours ago, WiseOne said:

With the Frog, Br can be as low as 1,

and that does not leave enough of a reserve of active, fast acting sanitizer in the water. Silver is not fast acting and has no action against viruses. Every bather adds urine, feces, and sweat (chemical very similar to urine) to the water no matter how clean they think they are and can quickly deplete sanitizer reserves. This is why I am not a fan of 'mineral' (metal ion) systems.

 

15 hours ago, WiseOne said:

What happens to the sodium bromide with addition of oxidizer (Cl or O3 or non-chlorine shock); does the bromine dissipate with use or convert back to NaBr; what is the effect of sunlight on the bromine reserve and active bromine; etc. 

There is a pinned thread by me on the use of three step bromine that does touch on the chemistry, along with a pinned post by me on lowering TA which does explain the chemistry . Bromide ions from sodium bromide are converted into hypobromous acid (active bromine sanitizer) by an oxidizer. When the bromine sanitizer is depleted it reforms the bromide ions and the process repeat.Some of bromide ions can be converted into bromate, which does not convert back and forth, and deplete the bromide reserve. Ozone is the oxidizer most likely to do this.

Sunlight has no effect on bromide ions but will deplete bromine sanitizer, which cannot be stabilized against UV like chlorine can by the use of cyuanuric acid. With a covered tub this is not an issue. Also, if you are using bromine tabs (which are mostly chlorine, btw) the dimethylhydantoin (DMHD)tends to 'stabilize' the bromine to make it more long lasting since sodium bromide can be eventually destroyed by repeated shocking with high levels of chlorine along with exposure to UV unless DMHD(which is how sodium bromide based algaecides work). Once DMHD is present it seems to help prevent the oxidation to bromate when compared to sodium bromide.

[WiseOne]

Thanks again. I actually mostly use a pool master 5-way test kit (solutions and titration). I realize that it doesn't give me the resolution that would be helpful for the sanitizer, and I will ultimately invest in the Taylor 2006 or the TFP equivalent. The pool master kit does give me a titrated total alkalinity reading. And isn't the pH readout on the Taylor also a color comparison readout, so depends on my ability to distinguish the colors?

If so, the only differences I see are the FAS / DPD test for the sanitizer and a calcium hardness test. 

Totally makes sense  what you say about the low sanitizer level not being sufficient. I am the only user of my hot tub, so maybe not as big an issue as for some. Are there any drawbacks to using higher bromine levels, such as respiratory or skin irritation?

[waterbear]

On 3/21/2024 at 2:21 PM, WiseOne said:

I actually mostly use a pool master 5-way test kit (solutions and titration).

OTO or DPD kit, they make both. (OTO has yellow color chips on the sanitizer side and DPD had red. DPD can bleach out and read low when it is really high. 

On 3/21/2024 at 2:21 PM, WiseOne said:

I will ultimately invest in the Taylor 2006 or the TFP equivalent.

Get the Taylor. I have both (and had input into the design.beta tester when I was a Mod at TFP). Get the Taylor.

FWIW, the TFP kit is pretty much a copy of the kit sold by Ben Powell of PoolForum before TFP existed. I also have that kit. They all use Taylor reagents. The TFP kit buys the reagents in bulk and repackages them. If your Poolmaster kit is OTO (yellow color block) you really don't need the included Taylor K-1000 OTO test kit included with the TFP kit. If you really want one I would buy it separately along with a K-2106 (for bromine) You can also get a K-2006 to test for bromine by doing the free chlorine test and multiplying the results by 2.25. Since k-2006 has a resolution of .2 ppm with a 25 ml sample it is going to give much more precision if you insist on running your bromine so low.

On 3/21/2024 at 2:21 PM, WiseOne said:

And isn't the pH readout on the Taylor also a color comparison readout, so depends on my ability to distinguish the colors

The difference is the reagent (and the quality of the comparator). The Taylor reagent will not convert until you reach above 10 ppm sanitizer and can be used up to 20 ppm sanitizer if another reagent is added. The poolmaster kit is pretty useless for testing pH when the sanitizer is much above 5 ppm.  The Taylor has a much better color block that is easier to read and also includes acid and base demand tests that can help you determine exactly how much acid is needed to lower TA safely. There is also a difference in the TA indicator. The Poolmaster has a color change from violet to yellow and it can be difficult to read. The Taylor changes from dark green to bright red and is very easy to read. FAS-DPD is a MUCH superior testing method and does not have the drawbacks of DPD (bleachout and close shades of red) or OTO (shades of yellow that are hard to differentiate at low sanitizer levels). Test with both and you will see there is no comparison between the kits. No, I don't work for Taylor! I just feel they make the best water testing kit for pool/spa use and it's worth every penny!If you think the price is too high think about how much you have invested in your tub. It puts things into persepcitive.

On 3/21/2024 at 2:21 PM, WiseOne said:

Are there any drawbacks to using higher bromine levels, such as respiratory or skin irritation?

Bromine should be run at 4-6 ppm. If the tub is properly maintained, no. In fact, when shocking you can re enter the tub once the bromine drops below 10 ppm. As far as skin irritation, bromine is a sensitizer (chlorine is not) so it is possible to become allergic to bromine. Non chlorine shock (MPS) is also a sensitizer and it is often used with bromine so I suspect that some of the cases of bromine sensitivity are really from the MPS used.

[WiseOne]

Much appreciated! 

[THE DUDE]

On 3/20/2024 at 8:11 PM, WiseOne said:

Thank you, Waterbear. I appreciate your precision. 

I had the water tested at a pool store with computerized readouts and verified my reading of test strips. With the Frog, Br can be as low as 1, so I'm happy with that, at least for now. My comment that it "feels balanced" was more of an intuitive sense based on water clarity, pH stability, lack of foaming and odor. 

I followed your suggestion of lowering pH and then raising TA. Things are much closer now. 

I wonder if you could put up a sticky with simple instructions of which chemicals and processes to use to routinely raise/lower pH and alkalinity. I thought I had read here previously that washing soda was good for raising pH with minimal effect on TA, whereas baking soda would raise TA with little effect on pH; and that aeration was an effective way to raise pH. You suggest here that washing soda is not useful for hot tubs. I'd actually enjoy understanding the (basic) chemistry of each addition.

The other sticky I'd love to see would describe the actual chemistry for a bromine tub. What happens to the sodium bromide with addition of oxidizer (Cl or O3 or non-chlorine shock); does the bromine dissipate with use or convert back to NaBr; what is the effect of sunlight on the bromine reserve and active bromine; etc. 

Thanks again. 

 

I was using my taylor kit and taking samples to the pool store. They came back with a chart all filled out in ink. It was always off from what my Taylor kit read. Had me second guessing  my readings as if i was not doing it right. I started a thread a while back on the 2006 kit.Took a sample from my daughters tub and mine( i had pretty fresh water) they came back and said her's was better and must have just had a water change becuase tds was lower. Not a chance unless they mixed up the samples. I know her cya was over 100 as she shocked once a week with enhanced shock that was 50% dichlor.  I started asking them if they check CYA and said no they just do TDS. Found out they just use strips, thats why they were so far off my taylor readings. Not knocking them but have not wasted my time using their "lab" anymore. Their ph was almost  always off and if i used what they recommended to add , would have put my Taylor readings off the chart.

[waterbear]

No surprise here. Pool store software is designed to see you as many chemicals at the can since this is how they make money. I worked in the retail end of the industry and tested more water than I care to think about. Some pool testing is better than others. If they are using strips they are either using a strip reader or just manually entering the readings. either way they are using strips. TDS is a bogus measurement and the fact that they don't test CYA is so they can sell you algaecide.  Overstabilized water allows algae to grow unless you are running higher FC levels to compensate for the higer CYA levels.