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Thread: SWCG Triclor tablet feeder combo

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    SWCG Triclor tablet feeder combo

    If you have an offline trichlor erosion feeder (connected via tubing) and an inline SWCG cell, would it matter where the feeder injection point was in relation to the SWCG cell? upstream? downstream? Is there any chemical reactivity? to consider for optimum performance?

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    JasonLion's Avatar
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    Re: SWCG Triclor tablet feeder combo

    That should be fine. I would hook up the tablet feeder before the SWG (closer to the heater/filter). In most cases it won't make any difference, but if the tablet feeder is hooked up afterwards there is a tiny chance that the tablet feeder could fill with hydrogen gas and explode.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: SWCG Triclor tablet feeder combo

    Thanks.

    So it would be similar to adding Calhypo tabs if all the wrong conditions prevailed.

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    JasonLion's Avatar
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    Re: SWCG Triclor tablet feeder combo

    Once whatever chemical you are using, trichlor, tablets, bleach, etc, are dissolved in the water they are all the same as each other (give or take the other chemicals that come along with).

    Having a tablet feeder can be handy if you want to raise the CYA level and lower the PH. I wouldn't consider using one all the time along with a SWG, but it can make a nice supplement to a SWG for special situations.
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    Re: SWCG Triclor tablet feeder combo

    We use them in combination and it seems to balance out the ph pretty well. Since the plaster drives up the ph early on and there is a waiting period for salt we installed the erosion feeders for customer convieniece during the infancy of the pool. We are now leaving them in place instead of removing them and it seems to be working out for shocking and winter sanitation. It would be nice is SWCGs could work at the 2000 ppm level. Thanks for the safety reminder.

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    Re: SWCG Triclor tablet feeder combo

    What is the downside of using them together on a continuing basis?

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    Re: SWCG Triclor tablet feeder combo

    Why would you? That would mean the salt system is undersized.

    Scott
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    JasonLion's Avatar
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    Re: SWCG Triclor tablet feeder combo

    Using a SWG and tablet feeder together over the long run works in several ways, but it is eventually going to raise the CYA level too high. I suppose you could lower the tablet feed rate low enough to balance out the natural loss of CYA, but at that point it would be turned so low that I don't really see the point in it. Depending on the combination also creates additional ways for the entire system to fail.
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    Re: SWCG Triclor tablet feeder combo

    When we use a SWCG its the Jandy 14 blade 40,000 gal system regardless of the pool size to maximize the life of the cell. Not only do the erosion feeders solve the early sanitation needs of the pool but they also provide low ph chlorine to minimize the need for customers use of muriatic acid and lower the cells production requirements. I really don't like explaining all of the safety cautions to customers about using MA or the fear in thier eyes during the explanation. Combining them seems to working out okay and if there was a SWCG that worked at lower salinity levels, it could provide the maximum comfort level for the customer and reduce the potential damaging consequences from the higher levels.

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    Re: SWCG Triclor tablet feeder combo

    Jason, it would be rare for a typical customer to reach 100 ppm CYA in less than 4 years if the only source of sanitation was an erosion feeder with trichlor tabs. It may be the rainfall in our area that dilutes the pools? I have a large number of customers with pools 10-24 years old that have never had to knowingly dilute the pool to reduce CYA levels with trichlor as the primary sanitizer. About 70% or more of them have or had ozone as a supplement. That is a sampling from general memory and not by any means a documented recollection.

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    JasonLion's Avatar
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    Re: SWCG Triclor tablet feeder combo

    Trichlor is wonderful for starting up fresh plaster, no question.

    Say your pool is open for 6 months of the year and you add 2ppm of chlorine each day using trichlor. For each ppm of chlorine, trichlor also adds 0.6 ppm of CYA, over six months (182 days) that would be about 218 ppm of CYA. Some of that will be lost to splash out, overflow, and backwashing, but usually not more than 20% or 30%.

    Using straight trichlor is more likely to work when the amount of chlorine added each day isn't actually enough to prevent problems. Less chlorine means less CYA and longer periods before you have a problem. The low FC level is then supplemented by weekly shocking using something that doesn't contain CYA. With that approach, things can be fairly stable for quite a while, but it costs more and there will eventually be problems.

    Very few people around here have problems with muriatic acid. Besides, there is no reasonable way to avoid needing muriatic acid during the first few weeks of a new plaster startup, even with trichlor. If there are problems, it can be purchased in a lower concentration, or the more expensive "no fumes" variant, which means either more carrying or more money but way less possible trouble.
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    Re: SWCG Triclor tablet feeder combo

    Jason, I don't have the chemical understanding to argue the math you have pointed out, but I do have a long term understanding of how my customers have maintained their pools and the problems they have encountered based upon their feedback. There is no doubt in my mind that those customers that are fastidious reach higher CYA levels faster than those that add chlorine when they see or feel the first signs of algea. Even the fastidious customers don't reach the levels of CYA you describe in that short of a time frame. This is indeed a mystery to me.

    In my uneducated chemical opinion, I think that bather load and exposure to the sun are not considered enough when factoring in the levels of oxidizers applied to pools.

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    Re: SWCG Triclor tablet feeder combo

    When I first got my pool around 7 years ago, I used Trichlor pucks/tabs in a floating feeder. The pool has a mostly opaque pool safety cover and has an oversized cartridge filter so no backwashing and only needs cleaning once a year (so minimal water loss). I also had a pool cover pump, no summer rains, and put winter rain water from the cover into the drain and not into the pool (at that time -- now I dilute the pool water with winter rains). My daily chlorine usage was low at around 0.7 (to 0.8) ppm FC per day though was as high as it was mostly due to 88F average pool temp (via solar heat). Nevertheless, after starting out with 30 ppm CYA, I got to 150 ppm CYA in just 1-1/2 seasons (about 10 months) of use when I began to get problems with cloudy water and higher chlorine demand (a nascent algae bloom) in spite of using PolyQuat algaecide, though only every other week. This was mostly because 10*30*0.7*0.6 = 126 ppm plus my initial 30 ppm. So this effect is very real and it does occur in real pools, but my situation had virtually no water dilution.

    In Charlotte, North Carolina, you get rain pretty much all year long ranging from 2.95" in April to 4.39" in March. The annual rainfall is 43.5" or around 3.6 feet. If this regular rain overflows the pools, then this continual dilution in a pool with average depth of 4.5 feet is around 55% annually. If the pools typically have higher CYA levels, then they might have fairly low chlorine usage and your swim season may be shorter as well. Let's say it's 1 ppm FC per day over 5 months. That would be around 90 ppm CYA so with the continual dilution the CYA level might never get that much above 150 ppm. I also haven't factored in any dilution from backwashing sand filters (especially in smaller pools where the volume of backwash is a larger percentage of pool volume), from splash-out, nor any CYA loss from oxidation by chlorine or bacterial conversion to ammonia over the winter (though that would show up as very high chlorine demand upon spring opening).

    Another factor is the ozone since that can sometimes lower the chlorine demand (sometimes it increases the chlorine demand -- depends on the bather and organic load). Also, the pools may have had rather low chlorine levels and therefore lower daily chlorine usage than I indicated above -- perhaps it was only 0.5 ppm FC per day (so 45 ppm CYA over 5 months). Pool water temperatures are also a factor where cooler temperatures (closer to 80F) have a lower chlorine loss rate (slower nascent algae growth; less outgassing; slower oxidation of CYA). And of course I've been assuming Trichlor-only for the chlorine -- if you use a mix of SWG and Trichlor, the amount from Trichlor will be lower than I assumed.

    Richard
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    Re: SWCG Triclor tablet feeder combo

    I myself began to have CYA -related problems very early on in my pool ownership. We used an Aquadoor over the skimmer. Had little if any water replacement. I didn't know the difference between the various granular shock - and would buy Dichlor. I never used liquid back then. Since trichlor was my only source of chlorine, and the pool frog instructions said to "shock weekly" in the summer... it wasn't long before my problems began and the pool store couldn't explain to me why I was having the issues I was - and what was their suggestion? "shock". which only compounded things because no one told me to use liquid, so I bought more dichlor.... They even once told me when I asked why they didn't test my CYA "don't worry about that."

    We have seen many posts on this forum from pool owners that used trichlor exclusively. Some insisted they did not have "any issues", but when questioned further they admit to using numerous other (sometimes expensive) products to assist with keeping there water clear that could probably be attributed to improper chlorination. They admit "i'd shock weekly"....why? they shouldn't have to shock weekly. There's no doubt if you understand how trichlor works you can use it successfuly but I'd guess the far majority of users don't understand it at all and spend a fortune keeping their pool "issue free". We do have many members here who use it here quite sucessfully, because they do understand it.
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    Re: SWCG Triclor tablet feeder combo

    Quote Originally Posted by chem geek
    nor any CYA loss from oxidation by chlorine or bacterial conversion to ammonia over the winter .
    Richard, I don't understand what you are saying here.

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    Re: SWCG Triclor tablet feeder combo

    Quote Originally Posted by renovxpt
    Quote Originally Posted by chem geek
    nor any CYA loss from oxidation by chlorine or bacterial conversion to ammonia over the winter .
    Richard, I don't understand what you are saying here.
    Cyanuric acid or actually isocyanurates can be oxidized, therefore descreasing the concentration. Similarly, CYA can be broken down into ammonia compounds which will form combined chlorine moietys and increase FC demand on spring start up.
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    Re: SWCG Triclor tablet feeder combo

    Does this breakdown only occur in colder water? Why wouldn't you intentionally do this to lower CYA levels if desired? Could ozone oxidize the isocyanurates and lower the CYA level? I guess I still don't fully understand but thanks for trying.

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    Re: SWCG Triclor tablet feeder combo

    It's my understanding that the oxidation is a low level thing. I think chemgeek was covering his bases in terms of how CYA can be lost. As far as bacteria eating CYA, this is an observation that has been seen in various pools, but i wouldnt say it's that widespread. If you have a high level of ammonia on opening, this is a distinct possiblity why.
    However, the largest loss of CYA is through dilution and backwashing. By far the largest reason people have problems with uncontollable algea is an overstabilized pool, though. If the CYA goes high enough, copious amounts of chlorine are needed to clear an outbreak. Levels that a pool store would not know how to deal with.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: SWCG Triclor tablet feeder combo

    It would certainly help explain why some my customers that fill the chlorinators based upon the beginning signs of algea have such low CYA levels. Its those very same customers that get a longer lifespan from the plaster.

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    Re: SWCG Triclor tablet feeder combo

    Yeah, I was just covering my bases. The chlorine oxidation of CYA is usually fairly slow. The only time we've definitively measured it is in a bunch of spas where at their hotter 104F temperatures it looks like they go from 30 ppm CYA to 25 ppm CYA over a month with average chlorine levels of around 4 ppm FC or somewhat less. Roughly speaking, this CYA loss consumes around 13 ppm FC per month even in spas that aren't used. Translating this into what happens in pools that are typically at cooler temps and lower active chlorine (hypochlorous acid) levels is difficult. If I were to hazard a guess, based at least partly at what I've seen in my own 88F pool, then the CYA loss is perhaps 5 ppm CYA (from 30 to 25) in 3 months resulting in a 0.14 ppm FC per day chlorine usage. At higher CYA levels you might see a proportionately larger drop, but this still isn't huge. It's possible there are chemical factors that can accelerate this process, but we don't yet know what they are.

    What we do know is that when a pool gets to zero chlorine, bacteria can sometimes grow and consume CYA converting it to ammonia. This is all described technically in this post and my personal experience with this effect is in this thread. Not only can this conversion be amazingly rapid, but it results in a HUGE chlorine demand from the resulting ammonia, let alone any algae that may develop. Some people open up their "let go" pools in the spring to find an unusually high chlorine demand even if their water is clear (and their CYA is much lower or zero) and it's most likely due to this bacterial conversion of CYA into ammonia.

    On the other hand, we have some people who report a significant drop in CYA over the winter without unusual chlorine demand or ammonia detected upon spring opening and we don't have any explanation for that yet other than the usual suspects of rain dilution, though this doesn't fully explain the amount of drop that is sometimes seen (it's possible for the ammonia to evaporate, but that seems unlikely).

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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