Borate application, redux

[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]

[chem geek]

There are plenty of spa owners at poolspaforum.com who use the Dichlor-then-bleach method (Dichlor used initially for about a week to build up CYA and then switch to bleach) and are able to keep their pH and TA fairly stable by having the TA be low (usually 50 ppm or a little lower), using 50 ppm Borates, and not trying to keep the pH much below 7.8 though some find the pH to be OK in the 7.5 to 7.7 range. Now keep in mind that these are residential spas so typically not used more than once a day. The water stays in good shape for about twice as long as Dichlor-only users (probably due to CYA build up making chlorine less effective). I would not characterize them as cesspools though it is true that they build up some organics that are not fully oxidized but the only indicator of that is a slowly increasing chlorine demand from around 25% per day to 50% per day. Ozonators are a mixed bag, but for high-use spas they help while for low-use spas they mostly just increase chlorine demand.

[PoolDoc]

If you have a pH of 7.8, a TA of 50 ppm, a borates of 50 ppm and a CYA of 40ppm(?), I'm assuming you'll have a very low CA? And thus, you'll have little pH drift from CO2 off-gassing during periods of aeration?

Are you / they adding dichlor (CYA) to spas because they are uncovered outdoor spas, or to reduce DPB formation? I get the "don't let CYA build up" thing.

So, I can see strategy of high pH + low CA + elevated non-CA TA + CYA control as a reasonable effort.

Can those results be improved by using that strategy, except switching to a very high CYA plus very high Cl residual? Something like 200ppm CYA plus 25 ppm Cl as a normal level? That might overcome the problem of insufficient total chlorine residual (in 300 gal water) to react with the bather goop of a couple of spa users.

-----

I've also realized I don't have any idea of what the 'normal' spa configuration is. In my area, even today, most spas are detached. But, I gather that attached spas may be more the norm in California and Florida.

- Are most of these in a shared equipment / unshared water configuration?
- Spill-over spas have to be in at least partially shared water configuration. Is it typically 100% shared, or partially shared?

I'm going to need to see if I can find some piping and control layout diagrams for these spas, to see have they've been design and should operate.

[waterbear]

If you have a pH of 7.8, a TA of 50 ppm, a borates of 50 ppm and a CYA of 40ppm(?), I'm assuming you'll have a very low CA? And thus, you'll have little pH drift from CO2 off-gassing during periods of aeration?

At PoolSpaForum we tend to recommend (with the Dichlor/Bleach method in an acrylic portable spa or one unattached to the pool with either dual or shared pump/filter so they are two separate bodies of water) TA of 50-60 ppm, borate of 50 ppm, CH about 130-150 ppm or higher (depending on how hard the fill water is, if the fill water is soft we don't recommend raising it above about 130-150 ppm since that amount of hardness is enough to deter foaming), and achieve a CYA level of 20-30 ppm by using dichlor and then switching to bleach for chlorination and shocking until time for the next drain and refill with spas (every 3-6 months,depending on usage). With a plaster inground spa with it's own plumbing, pump, and filter (either stand along or single/dual equipment with an unattached pool we basically keep the same recommendation but raise the CH to keep the SI in proper range. With a shared pump filter system with a spillover spa you essentially have a single body of water and one pump and filter. There might be a secondary filter or blower for the jets much like water features in a pool might ave a secondary filter but the main circulation is a single system and the spa is only isolated when being brought up to temperature and then used. This tends to be the most common configuration with both plaster and fiberglass pools and either plaster, fiberglass, or acrylic spas. This is essentially a pool with high aeration, not that much dfferent than a negative edge pool or a pool with water feature and running a low TA and maintaining the pH at a higher level and also adding 50 ppm borate is an effective way to minimize and slow pH rise and obtain pah stability for a longer period of time. It also requres a bit more attention to water parameters, testing and dosing. Adding a SWCG to the mix adds its own unique set of problems to minimize cell on time (by keepign CYA at the max) to lessen the aeration effect caused by hydrogen bubble generation and thereby also slowing the outgassing of CO2.

Are you / they adding dichlor (CYA) to spas because they are uncovered outdoor spas, or to reduce DPB formation? I get the "don't let CYA build up" thing.

Most portable spas are kept covered to maintain the heat and keep energy bills down,particularly since many are used in northern climates when pools are normally closed (We tend to be busiest at the forum in the dead of winter and have a LOT of Canadian and northern US members!). The idea of using a small amout of CYA is because of, as Richard likes to describe it to the members there when explaining the dichlor/bleach method), its 'buffering' effect on chlorine (making it less aggressive). IF the spa is heavy usage then the addition of a decent ozone unit or the use of MPS is recommended to help oxidize organics.
This has turned out to be a huge improvement in the sole use of dichlor, which we have foundcan lead to outbreaks of pseudomonas and other water born illnesses as the CYA level gets higher and higher.

So, I can see strategy of high pH + low CA + elevated non-CA TA + CYA control as a reasonable effort.

Can those results be improved by using that strategy, except switching to a very high CYA plus very high Cl residual? Something like 200ppm CYA plus 25 ppm Cl as a normal level? That might overcome the problem of insufficient total chlorine residual (in 300 gal water) to react with the bather goop of a couple of spa users.

Interesting idea but then you have to get over the hurdle of convincing users that the high FC/CYA combination is not going to kill them of make them sick and there is the real concern that it could void the warranty on their spa.
-----

I've also realized I don't have any idea of what the 'normal' spa configuration is. In my area, even today, most spas are detached. But, I gather that attached spas may be more the norm in California and Florida.

- Are most of these in a shared equipment / unshared water configuration?

There are basically three configuations:
1. unattached dual equipment--the pool and spa are two separate bodies of water and each have their own pump, filter, heater, etc. Not that common because of equipment costs and now usually seen when there is an existng pool and a stand along portable spa is added to the mix.

2. unattached shared equipment (normally only found with automation--there is only one pump,filter, heater, etc. and the are valve actuators on timers that switch between pool and spa so each can have a filter cycle during they day but they are two separate bodies of water that are treated individually. Spas in this configuration are usualy kept at temperature and covered to maintain the heat.

3. attached pool/spa and shared equipment (spillover spa)--this is becoming the most common configuration since it minimizes equipment costs and simplifies water maintenance since it is essentially one body of water. Normal configuration is water enters spa, spills into pool, and to filter from pool skimmer and drain. The spa drains are off. There are often also returns in the pool that are active. When the spa is desired there are valves or actuators that shut off the pool skimmer, drain, returns and open the spa drains (shutting off the pool, stopping the spillover) and making the spa the only thing in the loop. The heater is turned on to bring the spa up to temerature, which normally does not take very long. In places like Florida heat pumps and solar are often all that is needed but in more northern climates gas or electric heat (either main or as a supplementary spa heater) is often needed.

Normal operation is as a single body of water at pool temperature and after the spa is used the water is essentially 'dumped and changed". The main problem is the higher aeration, which can be dealt with by lower TA, tighter pH control, and borate.

- Spill-over spas have to be in at least partially shared water configuration. Is it typically 100% shared, or partially shared?

100% shared. not sure how you could even have a partially shared configuration.

I'm going to need to see if I can find some piping and control layout diagrams for these spas, to see have they've been design and should operate.

Try this Hayward Aqualogic Prologic manual pages 9-11. It has some diagrams that might help. Dual systems and shared water (spillover) sihared systems do not have to be automated but many are. Systems that are unattached but share equipment are not really practical without some form of automation to control run times for the pool and spa.