TFPC TA recommendations?

[gregsfc]

Should recommended TA levels for vinyl pools (70-90); and possibly other outdoor pools, be updated and further explained in Pool School? maybe under the section about TA? or as a note under recommended levels? A more complete explanation permitting lower, natural TA levels under curtain circumstances could save many members lots of work, and, instead of each of us learning one-by-one through forum inquiries that there is an easy way to solve this problem, this high out gassing scenario could be explained and parameters given to allow TA lower than the tables given.

There are many on here with vinyl liners (and other surfaces too) that are good students of pool school. We pay attention to detail when we execute what we've been taught. But there are some on here that have found, including myself, using the pool school recommended levels and trying to stay in the range for all the levels all the time as much as possible, that we constantly deal with rising ph, and subsequently, due to the fact that we are regularly adding acid doses to maintain ph, that we're regularly lowering TA out of range through these regular acid doses. And then, as good students, we know from what the calculator shows that we're going to need to regularly test and raise back up our TA to get it back in range. But this becomes an endless cycle for those of us in this situation.

I had this problem myself...I was going out of range on ph about 4 days a week and adjusting back to mid-range with 7 oz of MA each time. About every two weeks or so my TA would fall below 50, and being a good student of pool school and knowing the recommended levels for my vinyl pool, I would immediately calculate and raise my TA back to mid range (80); not knowing that being this good student was the root of my problem. I started a thread asking if it was okay to let my ph run around 8.0, since, in my mind, the ph was the culprit and not being chemistry minded, never even thought a moment about the idea that in some circumstances TA can be allowed to settle below the recommended level.

But since being given the great advice and help by Chem Geek and others on the thread I started, I have found at least five threads with the same or similar problem, with the same easy recommendation to fix it.

Here is a quote by Chem Geek on one of these threads...The lower the TA, the slower the pH rise from carbon dioxide outgassing until you get to the point of TA equilibrium with the carbon dioxide in water and air. However, in practice you only need to lower it to the point where the pH is reasonably stable (i.e. where the regular acid addition is not huge nor annoying). Also, if you have evaporation and refill, then TA from the fill water will increase the TA in your pool so lowering the TA a lot in the pool may be a but futile. You sort of what to get to a point of balance where you add enough acid to compensate for the TA rise from evaporation and refill and hopefully the pH at this balance is somewhere reasonable, perhaps 7.7 to 7.8 or so unless you're lucky to be able to have it lower around 7.5. Every pool is different since the amount of natural aeration varies.

With your vinyl pool you don't need to saturate the water with calcium carbonate so there is not a problem having a lower TA especially if you have 50 ppm Borates for additional non-carbonate pH buffering.

This was so simple once I started practicing it. If I start with TA at 80, and I lower ph to 7.5ish each time it rises above 7.8 with MA until my PH quits rising; then my pool will settle in @ 5 drops to clear, which means my TA is somewhere between 40-50, and all these crazy adjustments go away. But if I hadn't asked or searched and found a previous post with this simple answer, I don't think I would have found it on the site otherwise. And I wonder how many are executing this endless cycle trying to be good students of TFP and not even thinking to ask if there is an easier and cheaper way to maintain PH with a higher-than-normal outgassing pool.

So this is my question and point of this thread...If the proper TA level is in reality specific to each pool to create a PH equilibrium, why is it taught to be kept in a specific range? Is it because my situation and the others I've read about are uncommon? Or is because it is too complicated to bring this strategy up in pool school and best left to resolve on the forums? or is there another answer or something I'm not understanding?

 

[Patrick_B]

The ranges are there, mostly because they work in most situations, and generally they are good overall numbers for well balanced pools. I run low TA because I have extremely high CH, and very high TA/pH makeup. Not everyone does, so there will be exceptions to what works best for you. I could pontificate, complicate, and go on and on with minute details, but there really isn't much need. People need to be aware, and learn what is good for their pool and what works best for them. I emphasize, what is good for their pool, as these parameters can be extremely important in Plaster based finish pools.

It's like anything else in that Pool School would be a mile long piece of paper if we tried to cover every type of makeup water and pool situation. Some of our suggested levels aren't absolute gospel in every single situation, but we simply cant cover every scenario. There will always be exceptions like mine, and yours.

 

[woodyp]

"Each pool is different"
"RECOMMENDED levels"
"Ranges"

Like Patrick said, Those levels cover MOST situations, and as always, your mileage may vary. There is no substitute for learning how YOUR particular chemistry effects YOUR particular pool.
Understanding the consequences of varying from these suggestions is most important. It takes time to LEARN your pool. That said, my vinyl pool is most happy with TA @ 50 for PH purposes and causes no other ill effects.
Only took me 5 years to figure that out through experimentation when I finally decided to give it a shot.

 

[gregsfc]

Thanks. I get what you all are saying.

There are exceptions to everything. But there is someone asking about this creeping ph scenario at least twice per week on the forums, and each time someone asks, about 12 members jump in and say they keep their TA below recommendations, and that stabilizes their ph. Chem Geek usually gets involved and explains about different outgassing rates of pools. Maybe it's not as common as it seems to me; we're a large community with many, many members, but it just seems like it comes up alot. I work at a fish hatchery and we use baking soda as a buffer before we disinfect eyed eggs with iodine, so I understood before owning a pool, that the buffer keeps the ph from crashing when we add the acidic iodine, and so what we do at work is increase the TA to protect from a PH crash, but that's about all I knew from a chemistry standpoint.

My sister-in-law fixes people's green pools and equipment for pools in my area. She does not use TFP methods. She says that lots of people in our area are struggling with high ph pools this year, and most of these are folks using trichlor at least some of the time. So imagine if you take away an acid-leaning sanitizer and go to bleach only, which does not fight the PH creep at all. The problem gets more profound. I just wonder if there are lots and lots of people in certain areas of the country that should be running TA below 70; but instead, are either letting their pools run above 7.8 or use acid constantly, and then baking soda to fix the TA unnecessarily, because they don't know this level can be manipulated to save them work.

I've also read threads where people are assuming that most people using bleach are also consistently adding acid. I've been on threads where people are discussing that it's just something one has to deal with when using bleach as a sanitizer. They actually think that the bleach is raising their PH, when in fact, their pools are gravitating upward and the bleach just isn't fighting it. I used to think that it was bleach as well, but then figured out that the same thing happens when I use cal-hypo, but the problem slows when using trichlor or dichlor in my pool and that's because the acid counteracts the tendency for the ph to rise, and as soon as I take that away, I'm adding acid four times per week...That is unless I let the TA go way below 70.

 

[chiefwej]

Now, add in additional pH rise from the SWG, extreme high TA and CH in the fill water, and that equilibrium point becomes elusive. Add desert heat and extreme evaporation rates, and it's impossible. That's my situation. I can lower my TA with acid and aeration, but evaporation and high TA replacement water brings right back up in a short time.

There are just too many variables. It takes time and some experience with your pool to apply the basic principals laid out in Pool School. If it were written to try to cover many more situations, it would be too long and complex. Even now, I find that most sent to the forum, say its too complex and confusing. The goal of Pool School is to get them started, not provide a degree in chemistry (chemgeek will do that in the Deep End).

 

[chem geek]

For vinyl pools it would be easy to say let the TA drop with acid additions (or accelerate that with aeration at low pH to lower the TA faster) if one is experiencing a pH rise. 50 ppm Borates also help at least with the rate of rise if not the amount of acid over time.

For plaster pools it's more complicated because then you have to say to have a higher CH level and/or pH target. That's fine if one uses the CSI to figure things out but doesn't work if one is trying to simplify with simple ranges in a Recommended Levels table which is ironic because we clearly broke away from that for FC and CYA but seem to have a much harder time doing the same thing for overall balance using CSI. Simplicity has its costs.

There is also the question of fill water and evaporation where that can result in rising TA (and CH) so trying to have a much lower TA level may still mean adding acid, though at least the acid addition will be more limited to that required to keep TA lower.

 

[brauh01]

chem geek, should we be posting our CSIs then when asking for guidance/opinions? It might be the first step forward to moving away from Recommended Levels like the break away from FC/CYA. I do feel I have a handle on the FC/CYA but am very much still working towards a better handle on the pH/MA possibly TA and CH aspects of water balance. I don't recall ever posting my CSI, although I do not ignore it in the calculations. I find that "possible scaling" shows up more often than I'd like. BTW, thanks for all your help. Bill

 

[chiefwej]

chem geek, should we be posting our CSIs then when asking for guidance/opinions? It might be the first step forward to moving away from Recommended Levels like the break away from FC/CYA. I do feel I have a handle on the FC/CYA but am very much still working towards a better handle on the pH/MA possibly TA and CH aspects of water balance. I don't recall ever posting my CSI, although I do not ignore it in the calculations. I find that "possible scaling" shows up more often than I'd like. BTW, thanks for all your help. Bill

I agree that the CSI seems the more important number, but I would like to hear chemgeek' opinion on this. The CH only tells you how much calcium is in the water. The CSI tells you if that calcium will stay in the water or perciptate as scale. It also tells you if your water is becoming corrosive and will dissolve calcium right out of your plaster and grout.

TA within proper range allows you to better maintain a proper pH level, without it constantly rising or dropping. So while TA, and CH are important, it seems to me that CSI is the real vital number.

 

[chem geek]

The idea behind the Recommended Levels was to avoid having people calculate the CSI, even though PoolMath will do that calculation for them. However, if you are going to significantly deviate from those recommended levels (or even choose an unfortunate combination of them especially for SWG plaster pools) then you do need to look at your CSI since you could have it go significantly negative. It's easy to compensate for a low TA with a higher pH target and if needed a higher CH, if one has a plaster surface. For vinyl, it doesn't matter (i.e. a low CSI is OK -- it's a low pH that is detrimental to vinyl).

And yes, the ONLY reason we put in CH in swimming pools is to protect plaster surfaces (in spas it is added to reduce foaming). The CSI tells you if you are protecting plaster surfaces -- too low and calcium carbonate can dissolve from the plaster; too high and scale can form. We have a reasonable idea of when we see scale start to form in pools which isn't usually until the CSI gets to around +0.7 and by +1.0 scale is almost always seen (though some report that water is a little dull looking at +0.3 or higher). In SWG cells, scale can be seen at even neutral CSI since the pH at the hydrogen gas generation plate is much higher which is why we say in such pools one can go slightly negative in CSI (say to -0.2 or so) though another approach is to use 50 ppm Borates which cuts the pH rise in the cell roughly in half. In spas, we've seen scale develop as low as +0.3 in CSI possibly due to the hotter water temperature speeding up the scaling process.

The problem is that for plaster degradation it is usually a slow process so there isn't the same sort of clear-cut number to use. Low pH dissolves plaster faster, but a normal pH with low TA and CH would still dissolve plaster -- the question is how long that will take. Just because someone doesn't see a problem in months doesn't mean there won't be a problem over years and the idea is to have one's plaster last as long as possible. A -0.3 CSI has half the calcium or half the carbonate (or a product of the two that is half) compared to full saturation. At full saturation, there should be no net change in the amount of calcium carbonate in plaster pool surfaces.

 

[gregsfc]

Thanks everyone for the detailed discussion and opinions on this topic, and I see now how it would be very hard to incorporate a discussion about TA level parameters in the School; especially considering how complicated it gets with plaster pools.

I guess the biggest issue for me was, as someone who just found the TFP home page 15 months ago; someone who just read and started applying TFP methods without the need or time (back then) to get really involved in the forum; someone who thought at first that it really works as laid out using the recommended levels and mostly just adding bleach every day, but then later learned, as I got to know my pool better, that it wasn't really working as laid out. It took me a while to realize how quickly my PH was rising, and so for many months my pool was probably staying near, at, or above 8 most of the time. I don't know if this was a bad thing; I never had any problems during the period. One would think and not expect from just reading the school curriculum, that there would be this constant struggle to keep PH in range when one is following the instructions closely, and so for a long time, I just tested my PH about once per week, found it high, and adjusted it down. After discovering this phenomenon over time, I finally went to the forum (for the first time) and asked about high PH; why it might be happening? if it was necessary to keep it in range or is running a little high okay? I got mostly "yes it is necessary to keep it in range" answers to my inquiry; advice about keeping aeration to a minimum, and not much else except keep adding acid and keeping it in range. I also noticed lots of other members sounding off that it was a struggle for them as well. After about a week of no real solutions to my dilemma on the thread, I had adjusted down my PH about three times w/o bringing back up the TA (which I had never done before; never had a reason to believe it was permissible or related to the problem). I reported this discovery on the thread. The fact that my PH quit rising. CG then came on and brought up the TA reduction option--first time I even read that TA could be let out of range to fix this. I thought it was odd after learning this simple answer; if it was happening to lots of pool owners, why is this situation brought up only on a case-by-case basis on the forum. But now I see, since there are so many pool types that will allow for different tolerances to protect the surface, that it may just have to be this way.

 

[chem geek]

Thank you for explaining how you got to this point. This is not uncommon, but brings up the issue of how best to present information on this forum so let's talk about that.

If you were to do a Google search in the search box in the upper-right of TFP for "leave TA alone" you will find MANY threads going back to at least 2009 talking about leaving TA alone or letting it fall and find a place for TA where pH is more stable. Several moderators, including Richard320, tell people to leave their TA alone and not try and raise it. This is not at all new advice. The relationship between TA and pH has been clear for a very long time.

There are several problems with trying to set a TA standard. First is that every pool is different mostly because of the different amounts of aeration in such pools. Some pools have fountains, waterfalls, spillovers, etc. while some do not. Some pools use pool covers while some do not. Some get a lot of activity including splashing kids or regular swimmers while others do not. Some pools have a saltwater chlorine generator (it has hydrogen gas bubbles) and some do not. So some pools do just fine at higher TA levels while others require lower levels to be stable.

Second, is that some plaster pools tend to rise in pH from their plaster so that even lowering the TA the pH continues to rise and it can be hard to know in advance whether lowering TA will help or how much it will help. While lowering TA lowers carbon dioxide outgassing and that source of pH rise, it also lowers pH buffering so that any pH rise from other sources (such as plaster) will get worse.

Third, is that TA along with pH and CH need to be managed together to protect plaster pool surfaces and grout. So letting TA get lower is easier for vinyl pools without needing other adjustments, but for plaster pools one needs to balance with either a higher pH target or higher CH or both to keep the CSI in balance to protect the plaster surfaces.

Fourth, is that the TFP forum tries to simplify things as much as possible (perhaps too much) because most people don't want to know details about pool water chemistry nor have complicated calculations to figure things out. It has been hard enough to have people get away from looking at individual FC and CYA levels or ranges and to look at a Chlorine / CYA Chart when in fact it would be easier to just give people a range for the FC/CYA ratio, but even calculation of a ratio (i.e. division) is deemed to be too complex for many people -- not that they can't do it, but that they are scared away by any math beyond simply looking something up in a table. So asking people to calculate the CSI, even if done for them automatically in PoolMath is seen to be too complex or cumbersome (some moderators are vehemently against even referring to CSI in most cases).

Realistically, the TA level in the Recommended Levels for vinyl pools could have its range extended on the low end or have an asterisk that says some pools require a lower TA for more stable pH, but then what does one do for the plaster pools? For them one really cannot avoid using the CSI if they want to go lower in TA.

Many people coming to this forum just want a quick fix with a "just tell me what to do" without much understanding so that means it's already a hurdle to slowly walk them through some basic education, learning terminology, understanding the importance of accurate testing and getting a proper test kit, then understanding chlorine/CYA, and finally recommended levels for other water chemistry parameters.

So given that you've now crossed the chasm of understanding, how do you think this material could be presented in a way that doesn't turn off the majority of people but still provides enough information to get to more advanced adjustments requiring looking at the CSI for water balance (at least for plaster pools)? Should we lower the low-end of the TA recommended level for non-plaster pools to 50 ppm and put an asterisk by the low-end TA for plaster pools saying that if the pH tends to rise then click on a link that goes to a page that explains trying a lower TA first to see if the pH becomes more stable and if it does then adjusting one's target TA and CH levels to have a more balanced CSI as calculated by PoolMath?

 

[JoyfulNoise]

If I might make a suggestion, this is the last line of the Recommended Levels page -

If you have an indoor pool, high TA or high CH fill water, large amounts of aeration (negative edge), lots of direct sunlight, or fresh plaster you should expect to need some adjustments to these recommendations. For advice on what would be ideal for your pool please ask on the forum.

Perhaps it would be best to move that to the top of the page and add some disclaimer language to the beginning, like this -

Not all pools are the same when considering recommended water chemistry values. The values listed below have been found to be a range of values that works best for most pools. In some limited circumstance, TFP practitioners have found that using some values slightly higher or lower than the ranges given below works best for their pool. For example, if you have an indoor pool, high TA or high CH fill water, large amounts of aeration (negative edge), lots of direct sunlight, or fresh plaster you should expect to need some adjustments to these recommendations. If you find that these ranges are not working for your pool or if you would like advice on what would be ideal ranges for your pool please ask on the forum.

Then perhaps an asterisk can be added to some ranges with a footnote that describes them as flexible or gives a true lower limit, e.g., not letting the TA go lower than 40ppm to avoid pH buffering issues. If there is a mention of CSI, then perhaps it can be linked to a sticky describing what the CSI is, how it works and how it can be used as a proxy to help with balancing all of the other parameters (pH, TA, CH, etc).