Hot Tub Forum
Original => Hot Tub Forum => Topic started by: stuart on April 02, 2014, 12:04:59 pm
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Salt seems to be a new rage in the spa industry and many people are jumping on the bandwagon so over 2 years ago I decided to test it out in several different capacities...
I'll avoid brand names here on both generators and spa brands to avoid feeding into the whole "yeah but the brand I sell doesn't do that" argument. Just assume with my resources that I've tested your brand (because I have most).
First I ordered a generator that hung over the side and tried it on my personal spa. My initial reaction was that I LOVED the feel of the water and greatly enjoyed not messing with any chemicals for 3 months...then, in the middle of a blizzard, my spa tripped the GFCI and shut down. Being the tech I am, I immediately narrowed it down to the heater and started changing it at 10PM at night with wind and snow whipping around me. It wasn't that easy...when I pulled the heater I noticed that not only was the heater corroded through but my stainless steel heater tube (1 year old) was eaten through! So I put a new heater assembly in, changed all the damaged seals and gaskets and tried again. This time I thought I might be better off with a "built in" system which had more control even though I was willing to assume full responsibility for not being strict with my balance.
So after much work I was again enjoying my salt water hot tub...In addition, assuming that the damage was because I was just enjoying good feeling water and not taking care of balance and maintenance, I was ready to test some of the "Hang over" generators in the field on customer spas we serviced and spas that we knew would be balanced correctly.
Well, less then 2 months, my titanium heating element ate completely through once again! Not only that it looked it the salt went after it with a vengeance even though I was being meticulous about it! I hemmed and hawed...called other old timers, called the manufacture of the heater (who by the said they didn't like salt and wouldn't talk with me about it) and called the manufacture of both salt generators. I went back out to my spa and studied the situation, scratching my head and trying to understand because theoretically it shouldn't do what it did so fast! While looking I noticed that everything in my spa was grounded or "Bonded" except the heater tube in the plastic box (didn't reconnect the wire)...BINGO, my heater had become a "Sacrificial Anode" for the salt system! I grounded it and so far, I'm over 8 months with no issue, water is great and everything works fine!
So, we started selling the systems to everyone! Here is were the real battle begins...Many people have their own interpretation of our instructions and the instructions of the salt generator manufactures! We started having more heater issues then ever and most of them had holes in the flanges that are gasketed at the unions. In almost every case of failure however, we were able to determine the customer had done one of three things
1. They added to much salt adding it monthly or even weekly
2. They set their generators to produce way to much chlorine to the point that the parts smelled of chlorine when we changed them
3. They never checked balance.
So here is my synopsis...
1. I love setting in salt water, to the point that even if I had to put one heater a year in I would use it!
2. Salt is more corrosive...Water is a solvent, add salt its a better solvent
3. The water balance stays better with salt however if you let it go, you're in for catastrophy
4. Trying to do it on your own without the input of a professional will lead to failure unless you're willing to the experience of a tech or chemical expert.
Last, my biggest pet peeve throughout this process has been the sheer number of people that come to me and say "do you offer salt systems like the guys up the road because we can't deal with chlorine" Folks, salt systems ARE chlorine!
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Nice post, long time buddy, you need to check in a bit more often! ;)
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Also note that if you used ONLY the saltwater chlorine generator for chlorine and you never added any Cyanuric Acid (CYA) to the water either directly or via stabilized chlorine (e.g. Dichlor or Trichlor), then your active chlorine level is too high in the spa and that will also accelerate the corrosion rate. With some CYA in the water the chlorine strength is moderated. If you put in 30-40 ppm CYA then that should do well in the spa. You may notice that the hot tub cover lasts longer as there will be less outgassing of chlorine and you may notice your swimsuits, skin and hair getting less oxidized from the chlorine as well.
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Thanks for the comments it confirms my thoughts on the subject, I installed a drop in SWG (Saltron Mini) on my new to me 15 year old Hot Spring Jetsetter a couple of months ago (9 weeks to be exact), so far I love it, but am having some fine tuning issues, probably due to trying to get it to the balance point in such a small tub. Right now I have it set to run 4 hours per day which causes chlorine levels to build up slightly over time, but at 3 hours per day (next step down) it fails to maintain high enough chlorine levels. Still for $100 I think it was a great investment, I will just have to keep an eye on the heater and see how it lasts (it is the current style no-fault heater). I keep the drop in unit in the filter well, and have the unit set to run its 4 hours out of each 24 during the night, so peak chlorine level will be a few hours after my evening soak.
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Nice post, long time buddy, you need to check in a bit more often! ;)
I had to look at the date, I thought someone revived an old thread.
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Yes Bill....Stories of my demise have been greatly exaggerated! ;)
Sorry I don't get involved more however, a few of the more talked about manufactures here seem to think my opinion sways the public and don't like me stating my findings on an open forum. They complained to the magazine I write a column for and said they didn't want me writing in an unbiased industry publication if I was going to post public opinions on forums that were less then favorable to them.
Hopefully this wont tick off any salt people! It's my personal findings looking into using chlorine generators...if the Morton Salt girl files a lawsuit I'm screwed!
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chem geek does make a good point here....cyanuric acid is one of the least understood products used in spas because most consumer Chlorines already contain it and the issue is trying to keep it from building up with use.
Chlorine in spas needs to be stablized becuase of the hot water and volitile environment which is why I always suggest customers to get their products from a local dealer who not only carries stablized chlorine but can explain the danger of tri-chlors and cal-hypos that arent stablized. The sodium chloride being produced from salt generators would also be considered "Unstablized" and could use some CA.
Cal-hypo is one of the products that I see the most damage from in the field when used in spas.
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You were in New England area right Stew? Sorry we forget those less traveled here. But you've always been a respected member here. Screw them others..... ;D
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You were in New England area right Stew? Sorry we forget those less traveled here. But you've always been a respected member here. Screw them others..... ;D
He's in Colorado. I think the Bronco's play there, the same Bronco's that Seattle kicked the, well will just leave it at that 8)
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Chlorine in spas needs to be stablized becuase of the hot water and volitile environment which is why I always suggest customers to get their products from a local dealer who not only carries stablized chlorine but can explain the danger of tri-chlors and cal-hypos that arent stablized. The sodium chloride being produced from salt generators would also be considered "Unstablized" and could use some CA.
Cal-hypo is one of the products that I see the most damage from in the field when used in spas.
Just note that Trichlor IS stabilized chlorine. It just adds less CYA than Dichlor, but it's also quite acidic. The following are chemical rules independent of concentration of product or of spa size.
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.
The damage from using Cal-Hypo is likely due to the increased CH over time as that will eventually lead to scaling which can damage heaters since calcium carbonate scale on the heat exchanger prevents some of the heat transfer so would heat up the element internally potentially damaging the heater. One can also get scale on spa surfaces though that is reversible (still a pain, though).
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Jacuzzi Jim,
You're not referring to that time when the Cowboys stole the Broncos uniforms and snuck into the superbowl are you?
Chem Geek, I'm not sure "Over Time" is a good scenario on Cal Hypo...I can't tell you the hundreds of times I've seen damage to spas from the product. More specifically, HTH chemicals from walmart.
Every time I ask "are you using HTH chemicals?" people tell me "we've just recently started"....Could be people not telling the truth but with the sheer number of times I would have to point at the product being volitile to portable spas!
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So just to be clear, a single use of hth Cal-Hypo caused problems in the spa? What did it do?
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Not a single use but over a very short period it attacks the seals, dicolors and peels pillows, leaves a white film above the waterline and clouds the control screens.
My guess is that most have used it for at least a month by that time.
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I have witnessed this same thing happen Stuart. Probably a dozen or so times over the years
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Not a single use but over a very short period it attacks the seals, dicolors and peels pillows, leaves a white film above the waterline and clouds the control screens.
My guess is that most have used it for at least a month by that time.
I agree with Stuart. I would bet that the HTH chlorine is the number one culprit. They brand it as spa chlorine, and show a picture of a hot tub on the bottle. But, the product is 47% Cal Hypo, and not diclor. Most manufactures warranty states that the warranty is voided if Cal Hypo is used in the spa. I bet there are many people using that HTH stuff and don't even know they are using the wrong stuff.
I also think he hit the nail on the head when he said people think salt water is non chlorine or chlorine free. From my experience, most consumers think salt water in a non chlorine, chemical free water treatment, and that is obviously not the case.
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Chem Geek,
You're correct....I should have said tri-chlor and cal-hypo are "un-stable" in portable spas from my experience. I realize that stabilizer is added however, from my field experience, I can tell you that they are extremely unstable in a hot tub environment.
There are both plumbing manufactures and PVC glue manufactures that warn against the use of Cal-Hypo with their product.
I just worked on a spa that had relatively new plumbing yet after 4 months of the customer using tri-chlor tablets, the flex was brittle and blistered inside. it actually split the flex between ribs at the pump.
As always I enjoy your posts and your obvious knowledge of water chemistry however, I'm interested in your background and field experience with hot tubs vs. pools? There is no doubt that you have the science of it down, but I know that many of us see radical differences working on hot tubs daily and have learned the hard way that pool chemistry is a whole different animal.
I'm also interested in your thoughts on what you've seen in the field from different brands of spas and the affect of tri-chlor or cal-hypo on their plumbing.
Thanks ahead of time....
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I own a pool, not a spa, and I do not work in the industry. As for field reports, they come from the tens of thousands of people reporting on forums and from service people reporting on such forums as well.
Trichlor inline chlorinators are made of PVC but that's hard PVC and not the flexible kind of piping which may be more susceptible to acidic conditions. Having Trichlor introduced in a way where it gets well mixed should not be a problem, but having it in a skimmer when circulation is off can have the high chlorine low pH conditions migrate to materials that are not resistant and can have problems. This is why even in pools one should not put Trichlor in the skimmer because the pump isn't usually running 24/7. For spas, Trichlor is normally not used because it dissolves too quickly and if people don't watch the drop in pH and TA, then then the pH can crash and cause significant damage. However, if added with proper circulation and if the pH and TA are kept balanced, there's nothing wrong with using Trichlor, but of course those are big "if's".
As for Cal-Hypo, the increase in CH can cause scaling and that's more likely in spas due to the higher water temperature that increases the Calcite Saturation Index so it takes less CH, all else equal, to cause scaling compared to pools. Unless one has very low CH with their fill water, then there's no reason to use Cal-Hypo and if one does use it then one has to monitor pH more carefully since it will tend to rise due to aeration of the water (see discussion of bleach below -- Cal-Hypo is also a hypochlorite source of chlorine so has the same issues one needs to consider, but it of course also increases CH which bleach does not).
Many of the recommendations from manufacturers come from rules of thumb assuming that spa and pool owners don't know what they are doing. For example, most spa manufacturers or spa dealers say never to use bleach for sanitation. In fact that is reasonable if one were to use ONLY bleach since the chlorine would then be too strong, but using Dichor initially or adding CYA at first will moderate chlorine's strength. Also, using bleach without first lowering the TA significantly and using an alternate pH buffer such as 50 ppm Borates can have the pH rise too quickly and that can cause scaling (depending on the CH level). So while the advice of not using bleach is sound for those who can't handle adjusting more than one or two things in a spa at a time, it's not absolute advice and there are many Dichlor-then-bleach users who have no trouble with their spas and get at least twice as much time between water changes.
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Again, thanks....I've worked in the industry for over 30 years but have very little pool experience. In the last several years I've started writing a column in one "Hot Tub Only" trade magazine in the industry. This was a milestone to those of us that have felt like the red-headed stepchild of the pool industry.
Most of the chemical programs that we had came from the National Swimming Pool Institute and, having them right in my home town helps me research with them. The PHD that writes the brunt of the training, such as CPO certification, is a friend, neighbor and a spa customer of mine so it gives me a chance to work direct with him. Even he was surprised, when we installed an aftermarket generator and ph controller on his last spa, at how much corrosion occurred. We are about to install a different unit on his current spa late this month and experiment with it.
The big differences in chemical maintenance in a spa is that it's a much more volatile environment with the heat, turbulence and sheer bather load. Spas have a tendency to have a much larger gap between PH and TA.
I can tell you that what you see in pools, text books and lab testing will not be the same in a spa and often I bring things to the table that confuses or even astounds the pool industry top experts.
I also stay in constant contact with the Bio-Chemist that holds the patent on Di-Chlor for our industry and try to bounce things off her.
Having said all that, I can tell you that even the manufacture of bromine feeders have found tri-chlor and cal-hypo to be volatile to there spa units...I've helped them test them.
As a pool guy, cyanuric acid is part of your routine and something you're used to however many old time spa guys, real industry pros, never deal with it. Theory, pool water maintenance and even drinking water testing mean little to us as we aren't little pools!
The fact that you don't have a spa and aren't an industry pro makes your posts even more appreciated as you have nothing to gain here other then trying to impart knowledge. Thank you
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Thanks for the compliment and your insight. One thing that is fairly constant between pools and spas is that industry folk in both don't really understand the chlorine/CYA chemistry. They don't think there's any need for CYA in indoor pools or in spas not exposed to sunlight because they only think about CYA protecting chlorine from breakdown from sunlight and forget that it significantly moderates its strength. That's a delicate balance because too low an FC/CYA ratio and algae can grow in pools (and even in spas if exposed to sunlight and not always kept hot).
So it's ironic that though some recognize that using Trichlor may build up CYA in pool, they don't think twice about using Dichlor in spas even though it increases CYA more quickly. If they do realize it, they don't worry about it because the water can just be changed. However, it does increase the risk of getting hot tub itch/rash/lung and the water can get dull/cloudy from chlorine not being able to oxidize bather waste quickly enough.
At the other extreme, you don't hear about any saltwater chlorine generator manufacturers talking about using CYA in the water for spas or indoor pools (they do recommend it for outdoor pools), yet the higher salt level will not only increase metal corrosion rates, but the full-strength chlorine with no CYA will also increase corrosion and be harsher on swimsuits, skin and hair, will outgas faster so degrade hot tub covers faster, etc. There is hardly any research on this (unfortunately) but this study (http://richardfalk.home.comcast.net/~richardfalk/pool/Corrosion_and_Swimming_Pools.pdf) did find that "Moderate levels of Cyanuric Acid effectively inhibit corrosion caused by high chlorine levels".
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You and I will differ greatly on a couple points however...
First, I will never recommend someone put bleach in their spa! I've seen it leave an ugly residue from other additives in the bleach and I've seen bad corrosion on spas from it. Funny, most pool guys I know are potentially ok with it however us old hot tub dinosaurs that have had to repair the damage time and time again in the field will always contradict that advice.
Second, I will turn everyone I can from trichlor or cal hypo in a portable spa no matter the reason you us it. I say portable spa because I've rarely seen the damage in the custom built in-ground units. This could be because they usually have a 1/4 of the plumbing or jets and usually have a feeder a long way away from the unit, plus they usually have at least double the body of water. Saying that however, I've replaced my fair share of heat exchangers from chemical damage over the years...
I know that theoretically there are several good arguments against my statements and even tons of forum groups that have so called experts spout statistics (usually biased towards what they sell) however, I would put my field experiences up against any of them!
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OK, Stuart, what sanitizer do you recommend in a portable spa? I've been a spa operator for 3 days now! I'm all ears.
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Mike, I'm using a salt generator...but then, like I said, I've replaced heaters and need to replace a pump seal. That's no big deal to me as I'm a tech and can do it pretty quick and I love the feel of the salt.
I'm not saying consumers shouldn't use salt, I'm saying it can be more corrosive and could even void warranty on some spas.
I've always been a fan of good old fashioned di-chlor...If you use it correctly it's hard to beat!
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Any comments on the Gecko in.clear with bromicharge? Is bromine less corrosive? Thanks in advance for any knowledge in this area.
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So, did you use dichlor exclusively in your spa, or did you switch to chlorine once your CYA reached a certain level? I heard you were a big fan of clorox bleach..
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First, I will never recommend someone put bleach in their spa! I've seen it leave an ugly residue from other additives in the bleach and I've seen bad corrosion on spas from it. Funny, most pool guys I know are potentially ok with it however us old hot tub dinosaurs that have had to repair the damage time and time again in the field will always contradict that advice.
We're not talking about "experts" at forum groups. We're talking about reports from real users. Nearly 60,000 of them registered at just one pool forum, for example, with half a million visitors per month during the summer. It's true that there are fewer spa forum users (across multiple forums).
As for bleach, I don't know what the people you are talking about have been using but one should not use bleach with additives -- do NOT use "splash-less", "outdoor", "fragrant", "heavy-duty", etc. since these additives do muck things up mostly causing foaming. Regular unscented Clorox bleach and regular unscented off-brand Ultra bleaches do not have "additives". There is a small amount of excess lye in bleach and chlorinating liquid while Clorox contains a very, very small amount of sodium polyacrylate.
Also, if such bleach users used bleach without adding any CYA in the water first, then as I already pointed out the corrosion rate WILL be higher because the chlorine is too strong since it is not moderated in strength if there is no CYA in the water. The proper way to use bleach is to first add CYA in the water and the easiest way to do that in a spa is to use Dichlor initially until the CYA level builds up to 30-40 ppm (after roughly 33-44 ppm FC has been cumulatively added).
And as I also mentioned, when one switches to using bleach one needs to be very careful about preventing the pH from rising too quickly. This is why one should significantly lower the TA level and use 50 ppm Borates when one switches to using bleach. Otherwise one risks calcium carbonate scaling.
I don't dispute your experience, but I do question whether the bleach was used properly (i.e. the right kind and building up CYA first and having additional pH buffering).
I guess I'll have to tell the many dozens (maybe over a hundred; I haven't kept track) of spa users using the Dichlor-then-bleach method and reporting great results with no problems after nearly a decade that they will have to stop immediately because their spas are corroding horribly. Or maybe not.
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First, I will never recommend someone put bleach in their spa! I've seen it leave an ugly residue from other additives in the bleach and I've seen bad corrosion on spas from it. Funny, most pool guys I know are potentially ok with it however us old hot tub dinosaurs that have had to repair the damage time and time again in the field will always contradict that advice.
I guess I'll have to tell the many dozens (maybe over a hundred; I haven't kept track) of spa users using the Dichlor-then-bleach method and reporting great results with no problems after nearly a decade that they will have to stop immediately because their spas are corroding horribly. Or maybe not.
Don't do that Chem geek. Your expertise for water chemistry speaks for itself, and I know I have learned a lot from you over the years, as has others. Just keep doing what you are doing. I know many have said they have used your bleach method over the years with great success. I personally don't use it or recommend it, but that doesn't mean I don't think it works either.
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I was being a bit facetious. It's true though that the Dichlor-then-bleach method is certainly not for everyone because it is more complicated to set up and is riskier if you don't manage it properly. Dichlor-only is very easy to explain and harder to screw up though even in that approach one can crash the pH and cause corrosion because Dichlor is net acidic when accounting for chlorine usage/consumption so the TA will drop over time, but such drop is slow and odds are that one gets close to doing a water change before the TA gets close to zero (and if one has evaporation and refill of water, then the TA gets brought up some to prevent it from crashing). It would take around 280 ppm FC cumulatively added to exhaust 100 ppm TA and one would normally have to change the water in a heavily used spa using Dichlor about that same time, given the dull/cloudy water at that point.
Also note that I believe that the saltwater chlorine generators for spas can also be made to work much better with less corrosion if the same principles were applied there, namely if CYA were added to the water to reduce the active chlorine level as that should reduce corrosion. Now the corrosion rate will still be higher than in a non-salt spa simply because the salt level increases corrosion rates, but it may be manageable for many spas that don't have low quality stainless steel or other components. Again, the key is CYA because with no CYA in the water, the chlorine will be far too strong unless one keeps a very low FC level which is very impractical to do in a spa since the FC changes quickly due to the low water volume so relatively high bather load. Also, the chlorine will outgas much faster with no CYA in the water so that depletes the FC faster and also degrades hot tub covers faster.
stuart is going off of his experience and as I noted it's perfectly valid and one should not question the validity of that experience if coming from a sufficiently large sample which I presume to be the case. I just take a different approach to looking at experiences of spa and pool users to try and determine why the experience occurred and using science, when possible, to determine the root cause for what is seen. That often lets one figure out what is really going on and sometimes lets one find a different approach that works well without the problems.
As an example, for many years TDS in pools was said to be the culprit for cloudy water and high chlorine demand or for getting repeated bouts of algae, but a scientific look at what is correlated with rising TDS shows that pools using stabilized chlorine have their CYA rise and the problem is not with TDS itself (which is mostly salt anyway) but with the higher CYA levels. The science shows that the active chlorine level that prevents algae growth and oxidizes bathe waste is roughly proportional to the FC/CYA ratio so as the CYA level climbs if one doesn't proportionally raise the FC level then problems can start to occur. The reason that algae doesn't always occur at low FC/CYA is due to other factors such as algae nutrient (phosphate, nitrate) levels.
As another related example, the pool industry touts that phosphate removal is necessary to prevent algae growth, but that is simply not true. A sufficient FC/CYA ratio prevents algae growth regardless of algae nutrient level though the pool is certainly more "reactive" if you get lax and let the FC/CYA level drop so the phosphate remover should be seen more like an algaecide or as "insurance" if one doesn't think they can maintain an FC/CYA ratio.
There are many, many myths that have been disproven over time or shown to have different reasons for occurring than originally believed. I absolutely believe that stuart saw corrosion in spas that used bleach. The question is not whether that occurred, but why it occurred and what can be done to prevent it. Though initially with the Dichlor-then-bleach method there was one user that got scaling because they didn't watch the pH and this was before I recommended using additional pH buffering of 50 ppm borates, since that time there haven't been problems from any Dichlor-then-bleach users without any reporting corrosion or other issues. That doesn't mean the method is for everyone -- it's not -- but the method does work without side effects and with benefits of much longer time between water changes since there is no buildup of CYA that would otherwise reduce chlorine's effectiveness as with the Dichlor-only method.
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chem geek, it's obvious that you are truly passionate about water chemistry. When I see you have made a post whether on this forum or on the others, I read it. Thank you for all your help in the hot tub world. I went from knowing absolutely nothing about hot tubs a month ago, to feeling pretty good about my water chemistry today.
stuart, now you remind me of the Minnesota Vikings. They've been playing football for a long time, and they still ain't worth a sh*t!
Now that was a joke! I am learning from all you guys with the years you have in the business. Thank you.
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Chem Geek,
My comments were by no means meant to offend you...as I've said, you really have nothing to gain so your sharing of knowledge is greatly appreciated!
You've made my point much better then I did...many other systems are much harder to manage then dichlor and your way of using bleach may be effective but again, I would never recommend it to the average customer. I see people every day that still have their balancing agents from the start up kit in a box by their spa a year or more after delivery and yet they tell me "I check the water every week and it's always perfect. Then they don't understand when I tell them their pump seals have failed.
I would also agree with you on CYA, I'm currently testing the system out with borate to see if it lessens the corrosion. I would love to get the salt gen manufactures together with the chem experts and the field techs to see if we can't make it work more effectively!
Topline Mike...Wow...I think with the reputation I've earned over the last 30 years doing this I really don't have to low blows like that from anyone!
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stuart, now you remind me of the Minnesota Vikings. They've been playing football for a long time, and they still ain't worth a sh*t!
Hey!!!!! I take offense.
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Chem Geek,
My comments were by no means meant to offend you...as I've said, you really have nothing to gain so your sharing of knowledge is greatly appreciated!
You've made my point much better then I did...many other systems are much harder to manage then dichlor and your way of using bleach may be effective but again, I would never recommend it to the average customer. I see people every day that still have their balancing agents from the start up kit in a box by their spa a year or more after delivery and yet they tell me "I check the water every week and it's always perfect. Then they don't understand when I tell them their pump seals have failed.
I would also agree with you on CYA, I'm currently testing the system out with borate to see if it lessens the corrosion. I would love to get the salt gen manufactures together with the chem experts and the field techs to see if we can't make it work more effectively!
e...Wow...I think with the reputation I've earned over the last 30 years doing this I really don't have to low blows like that from anyone!
No offense taken. Just trying to explain the different perspectives. You are absolutely right that there are some spa (and pool) owners that just refuse to do proper chemical maintenance so keeping things simple and safer is better for them.
You also picked up on the fact that the use of 50 ppm Borates makes sense to have in a saltwater chlorine generator spa. Lowering the TA to around 50 ppm and using 50 ppm Borates is a combination that significantly lowers the rate of pH rise, especially if you don't try and lower the pH below 7.5 and you let the pH settle in near 7.8 if it wants to. Saltwater chlorine generators output hydrogen gas bubbles and the increased aeration forces more carbon dioxide outgassing that causes the pH to rise. TA is a measure of the over-carbonation of the spa so lowering the TA lowers the rate of such outgassing, but since it also lowers the amount of pH buffering that's where the 50 ppm Borates come in. The borates not only buffer pH, but do so more strongly as the pH rises so are ideal in situations where the pH tends to rise such as when using saltwater chlorine generators or when using bleach (or any other hypochlorite source of chlorine).
As an added benefit, the borates cut down the amount of pH rise at the hydrogen gas generation plate roughly in half so that helps to prevent calcium carbonate scaling at the plate though that is more of a problem in plaster pools where one is trying to balance the calcite saturation index. It would also apply to spas where the CH is high in the fill water.
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I was a fan of borates before I tried salt...it gave me a very similar feel. Still not much of fan of CYA but I understand that it can stabilize chlorine generated by salt probably better then borates.
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We converted to a Salt System Chlorine Generator (Saltron Mini) about 3 weeks ago. We have only used the hot tub once since it was installed. Our PH and Alk are right on target and our salt is at 3000 ppm. Our hot tub is 550 gal. We have not added any stabilizer since the hot tub is covered and not exposed to sunlight. Initially, we ran the unit for 3 hours a day, then 4 and now we're up to 7 hours a day and still no free chlorine is registering on the test strip. The unit's max run time is 7 hours so we can't go up any further. Does anyone have any idea why we can't get any free chlorine levels? Please help.