Borate application, redux

[waterbear]

(this was originally posted as an answer, here: http://www.poolforum.com/pf2/showthread.php?14386 , but moved to the CS by me for discussion -PoolDoc)

I am going to assume you have a 5000 gal pool with attached spillover spa (mine is only slightly larger at 6500 gallons for the pool and 300 for the spa) and when you want to use the spa yo isolate it from the pool by turning valves but it is normally one body of water.
I also assume that the total gallons for both pool and spa is 5000,

I am going to give slightly different instructions for the borax and acid then PoolDoc did.
1. First, order some LaMotte borate test strips (easier to read than the AquaChek strips).
2. Next have a small kitchen scale handy since you will need to weigh out the borax.
3. For ever 1000 gallons you will need 60 oz by weight of borax and 30 oz by volume of 20 baum muriatic acid to go from 0 ppm to 50 ppm (to make things a bit easier call it 4 lbs of borax and a quart of acid. It will be easier to measure and close enough for government work since you will make final pH adjustments at the end and the borax does not to be at exactly 50 ppm.). Remember each box of borax is 4.75 lbs and NOT 4lbs.
So for 5000 gallon you will need 20 lbs of borax (4 boxes is 19 lbs..close enough)
You will also need 5 quarts of acid ( 1 gallon and 1 quart). It might initially have the pH a bit lower than 7.6 but it will rise on it's own so it's not a worry.

Before you add the borax get your TA adjusted down to 70 ppm and make sure your CYA is at the manufacturer's recommended maxiimum for your SWCG, ususally 80 to 100 ppm--80 for Intellichlor (both of these will help slow pH rise for reasons to lengthy to go into now.) You did order the K-2006 , right?

4. adjust pH to about 7.6
5. you are now ready to add the borax. Turn on pump. Dump half the amount of borax directly in the pool and then add half the acid by either diluting it in a bucket of pool water a quart at a time or by pouring it SLOWLY into the stream of a return that is not near the skimmer.
6. brush down the sides of the pool to mix everything
7. add the rest of the borax and acid in the same way, brush again.
8.circulate for the next 24 to 48 hours then retest borate level, pH, and TA. Borate should be 50 ppm or slightly above, TA should be holding at around 70 or 80 ppm and pH should be around 7.6 yo 7.8. If it is lower don't worry, it will rise by itself (as long as it is above 7.0)
If it is higher use your acid demand test to determine how much acid will bring it down to 7.6.
Your pH should now stabilize around 7.7 for an extended period of time. When the pH climbs above 7.8 add acid to bring it down to 7.6 but not lower (since the lower you put the pH the faster it will rise) The acid demand test in the K-2006 will help you at first to learn how much acid you will need but afte a while you will be able to 'eyeball it' and hit it pretty close.

When your borate drops to 30 ppm (from backwashing, splashout, etc.) bump it back up to 50 ppm. 12 oz of borax by weight and 6 oz of acid by volume will raise 1000 gallon 10 ppm.

It's really MUCH easier than it reads and it will help stabilize the pH in a salt pool. The main cause of your pH rise is outgassing of CO2. Lower TA means less carbonation in the water means slower outgassing means slower pH rise. Maximium CYA means less cell on time means less hydrogen bubble generation means less aeration of the water means less ougassing of CO2 means slower pH rise.

Borates introduce a secondary buffer into the water (and have other benefits such as their algaestatic properites) which works to lower pH while the primary bicarbonate buffer works to raise pH. Together they make the pH stay around 7.7 for a longer time than without borate in the water.

Hope this helps.

[PoolDoc]

Hi Waterbear;

There are a couple of things in your post I'm not sure about, and a couple of others I'm not comfortable with. I'm going to ask Richard to weigh in on the ones I'm not sure about.

1. You put a lot of emphasis on achieving a borate level very close to 50 ppm. I'm aware of some reasons to try to reach 50 ppm; I'm not aware of any substantial reasons to avoid reaching 75 ppm. So, my question is, are there good reasons to try to achieve an accurate 50 ppm, as opposed to simply reaching 50 ppm OR more?

2. It's my understanding -- and experience -- that a hot aerated spa, maintained at a pH of 7.6 or below will rapidly achieve a carbonate alkalinity near zero, and that any remaining TA will be from borates and CYA. I don't understand a basis for your statements suggesting that -- on a hot aerated spa with pH held below 7.8 -- it is practical to maintain a TA (with a CA component) of ~80 ppm.

3. It's my understanding that a buffer does not have a 'direction'. Rather, in the range of a buffer's activity (ie, at the points where conversion between acid states, such as -HCO2 <=> =CO3) you will have a bi-directional resistance to pH change, since change in either direction will either absorb or release a proton (hydrogen ion). Consequently, it's not true that "Borates introduce a secondary buffer into the water which works to lower pH while the primary bicarbonate buffer works to raise pH", though it is true that borates and carbonates have different ranges of high activity.

Unfinished - To be continued later this morning, and I'll add a thread in the contributors' section for a policy discussion on accuracy and adding acid.

[waterbear]

Hi Waterbear;

There are a couple of things in your post I'm not sure about, and a couple of others I'm not comfortable with. I'm going to ask Richard to weigh in on the ones I'm not sure about.

1. You put a lot of emphasis on achieving a borate level very close to 50 ppm. I'm aware of some reasons to try to reach 50 ppm; I'm not aware of any substantial reasons to avoid reaching 75 ppm. So, my question is, are there good reasons to try to achieve an accurate 50 ppm, as opposed to simply reaching 50 ppm OR more?
Borate is a bit toxic at higher levels (mainly to dogs) and the effective target has been found to be 30-50 ppm for a halogen sanitized spa or pool and and 80 ppm for a biguanide santized pool or spa (as determined in the test pools of the patent holders for the borate products on the market for pools and spas.)

Also, the dosing method (adding half and then the other half) is the one used by Proteam (the orginal borate patent holder) and it works well from my experience.

The reason we test the pool is so we know what we need to add, how much we need to add, and when we need to add it. The DUMP and GO method of pool care, IMHO, leads to more problems than it solves. Is this not why we recommend using a Taylor K-2006 for testing? If not then strips would certainly provide the precision we needed to balance water, even with their unreliability! Borate is not a one time addition any more than CYA or Salt is. While it is true that they do not move that fast we still need to test the level and keep it in range just as with any other water parameter and the effective range has been found to be 30 to 50 ppm. (

2. It's my understanding -- and experience -- that a hot aerated spa, maintained at a pH of 7.6 or below will rapidly achieve a carbonate alkalinity near zero, and that any remaining TA will be from borates and CYA. I don't understand a basis for your statements suggesting that -- on a hot aerated spa with pH held below 7.8 -- it is practical to maintain a TA (with a CA component) of ~80 ppm.

First, it was apparent to me that the OP has a combo spillover spa/pool that is a single body of water and when the spa is desired it is isolated by valves or actuators and the spa is brought up to temperature. I have a similar setup myself. Therefore, my recommendation holds. If it were an isolated spa we have found over at PoolSpaForum that with a spa using the dichlor/bleach method (BBB modified for the higher water temps in spas) that a TA as low as 50 ppm and the addition of 50 ppm borate provides good pH control (thanks chem geek!). (If traditional Dichlor or three step bromine or 2 step bromine with MPS shocking is used then the acidic nature of the dichlor, DCDMH, and/or MPS tend to negate this somewhat by their constant addition of acidic material. However, we have found that, even with these methods of spa care the addition of 50 ppm borate useful given the high aeration normally present in spas because of the aerators and jets.) However, the OP was describing rising pH from a SWCG (also from aeration caused by hydrogen bubble generation in the cell), which is not uncommon, and the recommendations I gave (TA 70, CYA max, pH window 7.6 to 7.8) DO and WILL help when done together by minimizing the ougassing of CO2 and the borate to 50 ppm provides an extra layer of pH control that will decrease acid demand in most cases by quite a bit if the main cause of pH rise is outgassing. If there is also other factors such as curing plaster that are the primary cause of the acid demand then the effect of these water maintenance parameters will not be as pronounced but will still help to a degree.

3. It's my understanding that a buffer does not have a 'direction'. Rather, in the range of a buffer's activity (ie, at the points where conversion between acid states, such as -HCO2 <=> =CO3) you will have a bi-directional resistance to pH change, since change in either direction will either absorb or release a proton (hydrogen ion). Consequently, it's not true that "Borates introduce a secondary buffer into the water which works to lower pH while the primary bicarbonate buffer works to raise pH", though it is true that borates and carbonates have different ranges of high activity.
While it is true that a buffer made from a weak acid and its conjugate base will absorb or release a proton as needed the actual pH of the buffer is dependent on the amount of the acid or base present. With the carbonic acid/bicarbonate buffer found in pools and spa most of the buffer exists in the form of bicarbonte ion at normal pool pH range (because of the constant ougassing of CO2 and therefore the constand loss of carbonic acid) and therefore the pH of the system will move toward 8.3 because it has a higher limit for the amount of hydrogen ions it can absorb than release.
The boric acid/borate buffer system is mainly boric acid at normal pool pH and therefore will tend to move the pH downward since boric acid does not outgas and the Henderson-Hasselbalch calculaton wil give us a lower pH. In other words, it can relase more hydrogen ions that it can absorb.
Because of this these two buffer systems together therefore have a tendency to move the pH in different directions, which is why they tend to stabilize the pH around 7.7.
Simplifed explanaton but basically correct.

Unfinished - To be continued later this morning, and I'll add a thread in the contributors' section for a policy discussion on accuracy and adding acid.

Ben, I am still working on my write up on using acid and base demand test that we discussed before. It was put on hold for a bit because of spammer attack at the forum I moderate and extensive water damage to my house because of a defective dishwahser that I am in the middle of dealing with so I don't have as much time as usual but I will have it done and emailed to you soon.

[chem geek]

Point 1: See the Are Borates Safe? thread for more details. The EPA limit for Borates is around 50 ppm due to the dog studies, a margin of error (MOE) of 100 and presumed small amounts of ingested pool water. It's all very conservative, but maximum label dosings would be no more than 50 ppm these days.

Point 2: The following table shows the equilibrium carbonate alkalinity vs. pH where the amount of carbon dioxide in the water is in equilibrium with that in air.

pH CarbAlk
--- ----------
7.0 ..... 3
7.1 ..... 4
7.2 ..... 5
7.3 ..... 6
7.4 ..... 7
7.5 ..... 9
7.6 ... 11
7.7 ... 14
7.8 ... 18
7.9 ... 23
8.0 ... 29
8.1 ... 37
8.2 ... 46
8.3 ... 59
8.4 ... 76
8.5 ... 98
8.6 . 127
8.7 . 165
8.8 . 216

However, the rate of carbon dioxide outgassing varies as the square of the CarbAlk so in practice the lower TA significantly reduces the rate of pH rise and does not need to be as low as the above equilibrium values. As waterbear noted, in practice a TA of 50 ppm is usually pretty stable in spas if 50 ppm Borates are also used (and along with 30 ppm CYA the CarbAlk will be around 30 with the pH at 7.7 to 7.8). However, if you've got heavy use of aeration jets in a spa, then an even lower TA may be needed.

Point 3: I disagree with waterbear on this one. I wouldn't say that there is any tendency of the borate buffer system to move the pH at all. It is the carbonate buffer system that moves the pH upward based on the out-of-equilibrium situation described in Point 2 above due to carbon dioxide outgassing. What waterbear is referring to in terms of up and down are the pH positions of maximum buffer strength (aka buffer capacity though it isn't really a capacity) which for the carbonic acid (really mostly aqueous carbon dioxide) / bicarbonate buffer system is at a pH of 6.3 while for the borate buffer system is at a pH of 9.15. So the carbonate buffer system gets stronger as the pH gets lower so it is great at preventing the pH from getting too low, at least until the TA is near exhausted. Likewise, the borate buffer system gets stronger as the pH gets higher so it is great at preventing the pH from getting too high.

[waterbear]

Point 3: I disagree with waterbear on this one. I wouldn't say that there is any tendency of the borate buffer system to move the pH at all. It is the carbonate buffer system that moves the pH upward based on the out-of-equilibrium situation described in Point 2 above due to carbon dioxide outgassing. What waterbear is referring to in terms of up and down are the pH positions of maximum buffer strength (aka buffer capacity though it isn't really a capacity) which for the carbonic acid (really mostly aqueous carbon dioxide) / bicarbonate buffer system is at a pH of 6.3 while for the borate buffer system is at a pH of 9.15. So the carbonate buffer system gets stronger as the pH gets lower so it is great at preventing the pH from getting too low, at least until the TA is near exhausted. Likewise, the borate buffer system gets stronger as the pH gets higher so it is great at preventing the pH from getting too high.

Actually, we are saying the same thing if you think about it. My wording was trying to put in more layman's terms what occurs. It is easier for most to understand 'moving the pH" since that is what they do with the addition of an acid or base and it is easy for them to think of a buffer as something that does that for them automatically.

[waterbear]

Point 1: See the Are Borates Safe? thread for more details. The EPA limit for Borates is around 50 ppm due to the dog studies, a margin of error (MOE) of 100 and presumed small amounts of ingested pool water. It's all very conservative, but maximum label dosings would be no more than 50 ppm these days.

As a point of interest Bioguard recommends 30 to 50 ppm of Optimizer for halogen sanitized pools and 50-80 ppm for biguanide santized pools (probably for the algaestatic action of borate).
Then again, we used to use simazine as an algaecide in pools until it was banned. I am sure Ben is familiar with it.

[chem geek]

In my post above "margin of error (MOE)" should be "margin of exposure (MOE)". It's too bad that I can't edit my posts after some time.

Yes, as shown in the Bioguard® Optimizer Plus® instructions, they recommend 50-80 ppm for biguanide pools. This is somewhat higher than the 50 ppm limit implied by Table 5 of the EPA report that has a 100 MOE for a roughly 350 mg/L sodium tetraborate pentahydrate product concentration which is equivalent to 350 * (4*10.8117/291.3) = 52 mg/L (ppm) Boron. I suspect that the biguanide dose rate is grandfathered.

As for the buffer explanation, I think it would be better to refer to the buffer as resisting moves in pH rather than moving the pH itself (at least for the buffer part of the explanation -- carbonates have a separate carbon dioxide outgassing effect that is not related to their buffering). The borates resist moves of pH in both directions, not just down, but since the resistance gets stronger as the pH rises it acts like a spring being compressed at higher pH just as the carbonate buffer acts as a spring being compressed at lower pH. So the carbonates resist the pH getting too low while the borates resist the pH getting too high even though technically they both resist pH changes in both directions at any given pH. A key point, however, is that the carbonates (represented by TA) are a SOURCE of rising pH in their own right, due to carbon dioxide outgassing, and that has nothing to do with their buffering capability -- it is an additional and unique effect that does not apply to borates. So substituting borates for carbonates as a buffer system makes sense to reduce a source of rising pH.

[waterbear]

I like that spirng analogy! Mind if I use it in the future?

[chem geek]

But of course...use it freely! The most important point, though, is that the carbonates are a SOURCE of rising pH in their own right. So while they buffer pH, they also CAUSE rising pH. That's the most critical concept to understand. Otherwise, if we only talk about buffers and how they get stronger in one direction or another, then people will think that they can balance each other out and that having a higher TA is no problem if you just have more borates. That isn't true, of course, though the borates may make the rate of the pH rise less, there will still be as much acid that needs to be added. The only real way to save on the amount of acid needed is to lower the TA (and/or have a higher pH target -- i.e. don't try and lower the pH as much).

The thing I don't like about the spring analogy is that it still implies some sort of pressure or movement when it's more like resistance to change. That is, though the spring will make it harder to compress, it isn't really causing the pH to bounce back the other direction after you stop adding acid or base. It's more like viscosity where it gets more viscous so harder to move as you get closer to the pH buffer's strongest pH point, but once you stop applying acid or base, it stops moving (except for the carbon dioxide effect which is essentially removing carbonic acid from the pool).

[PoolDoc]

I've tried to write a full response 4x now but I keep getting side-tracked. Sorry!

I'm going to try again, but rather than writing a response, I'm going to try to summarize the issues and state my view. If you disagree, and can prove me wrong, or justify an alternative position or conclusion, I would be grateful of you do so. I don't like being proved wrong, all that much, but I like it much better than BEING wrong!

Probably, each point could be its own thread; feel free to spin off a thread if that will avoid confusion.

OK. Issues.



0. (This is not really a conclusion; just a bit of information.) At PF, for every person who registers, there are more than 25 who just lurk! That's good! We could not answer 25x as many questions as we do.

So, some of my positions here, reflect the sense I always have of 25 lurkers with pools, who are reading over my shoulder.

1. At PF, I prefer the least accuracy and simplest explanation consistent with both truth and function. Chem_Geek and I have talked about this before: he prefers more accuracy. I have not always thought this way, to the degree I do now. But even when I was working on the testkits, my ORIGINAL goal was mostly to get pool owners out of pool stores, and I felt I needed a more accurate kit, in order to get pool owners to trust their results.

2. I do NOT want posts at PF that suggest that pool owners measure 32% muriatic acid, beyond 1/8th or 1/2 of a gallon jug. I've opened a thread on this in the Contributors' section. If you disagree, I welcome your input, but please take it there.

3. I decided a long time ago to prefer the "dose, test, dose, test . . ." (DT) approach to pool chemistry over the "test accurately, calculate, measure carefully, dose" (TCMD) approach that pool stores claim to use. The ONE exception to this is chlorine dosing, where pool owners often need enough (or a little more) RIGHT now.

One reason (among many) for my preference is that the TCMD approach can only work consistently if the TEST are accurate AND the CALCULATION is accurate AND the MEASURING is accurate AND the pool volume numer is accurate. In my experience, it's rare that all these coincide.

4. Given the 3 points above, and given my very considerable skepticism about Girvan's 'studies', I can't see any benefit to the elaborate 'official' program pushed by Proteam. Maybe there is one, but you'll have to explain it do me. I don't doubt that it works; I just don't have any reason to think it works better than a simple DT approach.

5. I don't like spas, and haven't for a long time. Basically, I think you can divide spas into 3 groups:
+ Spas with full-time trained attendants or with functioning ORP/pH controllers, calibrated daily, that trigger reliable bleach and acid feed pumps;
+ Spas attached to pools, that SHARE water and treatment with the pool; and
+ Heated cesspools. (I think this is by far the largest group!)

I'm open to the possibility that a spa with an attached high-output ozone feeder could represent a 3rd group of spas that ARE sanitary. Under those circumstances the LACK of a sanitizing residual would be good, since you wouldn't have to deal with the ozone equivalent of the spa with 200ppm Br. (Been there; somebody else did it; did see the saggy bathing suits!)

6. We have enough PF users with IG pools and attached spas, so that I've got to get over myself, and create space for spa answers that are good, or at least, as good as they can be. (I still don't see any way that, given how people are, there's anyway for non-automated, non-attended stand-alone spas to be anything but cesspools . . . or chemical fire-pits!

7. There is no way to maintain carbonate alkalinity in a spa IF pH levels are maintained in the 7.0 - 7.8 range. I discovered that 20+ years ago, after installing a bleach / acid feed system, and an ORP/pH controller on the Marriott in Atlanta. I balanced everything just so; turned on the feed system, adjusted it; turned on the controller and calibrated it . . . and then turned on the blower. 10 minutes later, my 120 ppm TA was below detection with the Lovibond tablets I was using then. Rebalance; repeat; same result. Do over, again. Fortunately, I had my Eureka! moment, before going for a 4th time.

8. Pools with attached spas, are pools with super-high-output aeration. If the spa is used regularly, CA cannot be maintained on those pools, either.

(I made a BIG mistake in my answer in the thread that triggered this: I assumed that, since the OP said his pH rise was related to his SWCG, it was. But, based on the info we have from him, it's just as likely it was from his spa aeration.)

9. If we're going to deal with spas, we need to make SURE we know which type the OP is talking about: (a) stand-alone, (b) shared equipment, but NOT shared water, (c) integrated. In most cases, only integrated spas can be consistently sanitary. And, we need to make sure that WE have made clear which type it is, so the lurkers will understand.

10. I need to write a "using borax" page that includes borax hazard info. Then, we need to reference that page in borax posts, partly as CYA, and partly so people who are frightened of chemical hazards will be able to trust us.

11. I think Chem_Geek settled it, but I'll state it: buffers cause water to resist pH change; they do not cause or push pH change themselves. In water systems that already have a drift, due to SWCG use, aeration, or trichlor use, different buffers will great different 'stop' points in the pH drift. Buffers (that I know about) in pools include carbonates, cyanurates, phosphates and borates. I don't think phosphates are deliberately used anymore, with the demise of "Perfect pH".

(I like the viscosity analogy much better; an alternate might be driving on concrete vs driving in loose sand, or something along that line. It might be possible to apply the spring analogy to the way CA 'disappears' when the pH drops, but 'reappears' when it goes up. But, that just popped into my head; I haven't considered it.)

12. . . . that's all I can think of, now.

[Gotta go -- will check for spelling & other errors when I get back]