It is very likely Eriochrome Black-T (Sodium 1-[1-Hydroxynaphthylazo]-6-nitro-2-naphthol-4-sulfonate)
It’s a complexometric indicator azo dye, which means it changes color when it bonds with a metal ion. It’s red in solution when calcium ions (Ca2+) are present then turns blue when they are removed. The R-0012 is a mixture of EDTA/CDTA that more strongly binds up calcium. So the R-0012 effectively “removes” the calcium and the R-0011L indicator turns from red to blue.
Joyful Noise, thank you!!!! I read your post about testing for borates and you mentioned the Bromothymol Blue reagent. I remembered the RO11 in my T100 kit and simply wondered what it was. I ordered all the stuff needed yesterday for testing borates AND ordered boric acid to put in my pool. I can't wait to get started. I have been toying with the idea of adding borates to my pool for some time now. One question. Pool math said 50ppm of Borates will add 110 TA. (For the record, I dislike the new calculator. It is not as intuitive as the old pool math! I want the old one back!! ) I was of the understanding that borates would only raise TA by a little bit. If I am starting with a TA of 60, should the effect be more like 70?
Starting numbers before adding boric acid.
My purpose for adding borates is constant rise of pH due to infinity edge causing aeration and high pH fill water.
“If there are Borates in the water, then the following equation is the primary one:
B(OH)3 + H2O <---> B(OH)4- + H+
Boric Acid + Water <---> Borate Ion + Hydrogen Ion
where at a pH of 7.5, 97.6% is Boric Acid while only 2.4% is Borate Ion which is why this has a negligible effect on TA. At 50 ppm Borates, the TA is only increased by around 5 ppm at a pH of 7.5.
One misconception is that TA is a direct measure of pH buffering. This is not true. Total Alkalinity (TA) is only a measure of pH buffering CAPACITY and even then, only in one direction, specifically against a lowering of pH. A different measure known as Total Acidity measures the pH buffering capacity against a rise in pH. The borates do not count much towards Total Alkalinity, but they count a lot towards Total Acidity meaning that they have a greater capacity against a rise in pH than a drop in pH. That doesn't mean they don't resist a drop in pH, but rather they don't have as much capacity and will "run out" sooner after which the carbonate buffer system is effectively the only one left.
All of the above is the theory, but what is really important is what happens in practice. The following shows the effect on pH when adding 2 cups of 31.45% Muriatic Acid in 10,000 gallons:
TA 50, CYA 0, Borates 0: pH 7.5 --> 6.96
TA 100, CYA 0, Borates 0: pH 7.5 --> 7.17
TA 150, CYA 0, Borates 0: pH 7.5 --> 7.26
TA 100, CYA 80, Borates 0: pH 7.5 --> 7.26
TA 100, CYA 0, Borates 50: pH 7.5 --> 7.26
TA 100, CYA 80, Borates 80: pH 7.5 --> 7.31
This shows that having 50 ppm more TA or 80 ppm CYA or 50 ppm Borates are roughly equivalent in terms of resisting a drop in pH. Now let's look at what happens when we add 7 ounces weight of lye (sodium hydroxide) which is a pure base roughly equivalent to 17.6 ounces weight of soda ash / pH Up (sodium carbonate) or 35.1 ounces weight of Borax though these latter two have other side effects on TA.
TA 50, CYA 0, Borates 0: pH 7.5 --> 8.58
TA 150, CYA 0, Borates 0: pH 7.5 --> 7.88
TA 100, CYA 0, Borates 0: pH 7.5 --> 8.10
TA 100, CYA 80, Borates 0: pH 7.5 --> 7.90
TA 100, CYA 0, Borates 50: pH 7.5 --> 7.74
TA 100, CYA 80, Borates 80: pH 7.5 --> 7.70
From the above, you can see that Borates are a significant pH buffer resisting a rise in pH much more effectively than a lowering in pH and much more powerfully than the carbonate or cyanurate buffer systems. Here, having 50 ppm more TA is slightly better than 80 ppm CYA but 50 ppm Borates is even better at resisting a pH rise.”
SO I was wrong in thinking that by keeping a lower TA around 60, plus 50ppm Borates was going to be better at buffering pH rise? So are you saying I should have a TA of 100? I have a SWG system. In "Pool School" is says to keep my TA between 60-80. Just when I thought I was understanding all this. I thought TA below 60 and the pH swings around wildly, and at TA above 80 and the pH tends to rise. Higher the TA, the higher the pH wants to go. Now I am learning I am wrong? No, now I am confused. I have an infinity edge which is constantly aerating the water. More aeration= pH rise. Now I am confused.
@Sharkygirl Stay with your target of TA 60 add add your Borates.
You don't need to know the whys. TFP is about simple guidelines. The chemistry like above should be kept in the Deep End. If you want to explore the science behind things you are free to review that section.
TA in our pools is mostly carbonate alkalinity, it mostly prevents your pH from dropping. A high TA increases CO2 in your pool which vents off causing the pH to rise faster. Your infinity edge also speeds up the CO2 venting. To minimise this you definatly want to target a TA of 60 - 70ppm. The borates on the other hand are best at slowing the pH from rising, and very beneficial in the SWG cell - a win win really.
TA and pH-working hand and hand-each pool is different.
It might take some tweaking and watching but once you find the sweet spot things could level out. Your pH will tend to rise from your edge just as you stated. That is the price you will pay for that wonderful feature.
Take notes on what your levels are. Let things ride for a week or so on the TA. Adjust the pH as needed. Then adjust the TA to the next 10 (take it from 50 to 60) for the next week or so. See what that does for you pH.
While you are doing this make sure to watch the CSI to keep your plaster safe. The water temp will play a big role in the CSI to be very aware of that as the weather changes.
You got this! Keep asking questions and sharing what you find so we can use this to help others!
We could get into the chemistry but let’s not. Quite simply, aeration or agitation of the water leads to increased outgassing of dissolved CO2 (think of your poolwater like a can of soda). When CO2 leaves the water a series of chemical reactions happen and pH increases. It happens in all pools and all water to a greater or lesser degree.
Important question - do you have the ability to automate and shut off your infinity edge? If so, it should remain off most of the time.
For example, my spa spills over into my pool. I can control that and I run it only about 1 hour/day. That’s all the turn over my spa needs froma sanitation standpoint and it keeps my water aeration to a minimum.
That's a really good idea. Yes, I can by manipulating my main drain and trough drain. I don't have an automated way to do it. However it would be good to open and close those drains more often because they do tend to get stiff. Thank you JoyfulNoise for being so patient with me. I have learned a lot on this forum and it is because of people such as yourself. Your explanations are so easy to follow and understand. If you are not a teacher, you should be! Thank You.