Question about combining SWG with trichlor for larger pools

[BasicTek]

When I bought my SWG I got one that was 4x my pool size and I replaced my inline chlorinator relying on just the SWG. I've never seen it suggested but as the summer rain and hurricane Irma have removed quite a bit of CYA from my pool in the last 3 months, I've been floating a bunch of leftover pucks to build my CYA back up. I've received another benefit of no more need to add MA, as the trichlor seems to push my PH down about = to what the SWG would raise it. I'm wishing I kept the chlorinator as I could control how many pucks are dissolved weekly and adjust my SWG to keep chlorine levels where I want them (as opposed to using a floater).

When folks come on here with very large pools or a SWG that was not properly sized I've never seen the suggestion to use an inline chlorinator to supplement FC, at the same time combat PH rize, and maintain CYA. Using pool math it would be easy to calculate how many pucks would be needed per week/month. Is there anything wrong with this approach or any inherent issues it could bring? If following TFP methods and testing properly/regularly I would think this could be a feasible solution. For instance if someone had a 30K pool they could get a 40K SWG and inline chlorinator. Using pool math I would think they could dissolve 2 pucks a week (under normal conditions more if needed) supplementing FC, combating rising PH and maintain CYA....

Anyway just wondering others thoughts on this. Maybe it's too complicated to suggest and maintain.... I'm just looking at the #'s and have very little actual experience...

 

[proavia]

As long as YOU know what you are putting in your pool and YOU are maintaining the proper levels, it should work fine for YOU - in your location.

That being said, it many be a bit too confusing for some - and it probably wouldn't work for me in my location (desert southwest).

I'd still suggest a SWG 2 to 3 times the pool volume. More versatility and possibly longer lasting, in addition to maybe saving pump run time.

 

[Donldson]

Maybe it's too complicated to suggest and maintain....

Bingo. Sure, if your pool needs chlorine, acid, and CYA added in slow amounts tablets are fine. But it is important on the site that we don't over complicate things. Someone who is using a proper kit for the first time and is a bit overwhelmed should not be attempting to calculate the adjustments of 3 variables at one time. For the new person starting out it is much easier to adjust 1 thing at a time, which means using bleach, MA, and CYA separately.

Remember, everything written here is considered "advice" to those first reading it. I have seen some very strange assumptions made by people who read one thing someone said in a thread from years ago and took that as an official TFP stance. So we keep it simple and those who wish to pursue more advanced ideas are welcome to. It is, after all, your pool.

 

[BasicTek]

That makes sense, I started thinking while typing the op "how would this come off in a response" and it's hard enough to help people realize the info from pool stores and other sources is not the best, now try combining some of that info with this.... it would probably be a big mess.

Thanks for the replies.

 

[Pemolis]

I’m beginning a plum of a swg in my pool and currently use a stenner plugged into the puck dispenser to dispense chlorine (will be switched over to dispensing acid before the swg). I have a inline chlorinator but chucking it as my solar breeze can do pucks.

Long as you keep the cya in check, don’t think anybody cares.

 

[BasicTek]

my solar breeze can do pucks.

Ya I ended up using a floater. I've floated about a dozen pucks this summer and still my CYA is lower than I'd like (60-70) With our rainy summer and hurricane I lost about 60 CYA from June (SWG conversion) to now. What I really like is when I'm floating pucks I no longer need to add MA. I'm maintaining my PH at 7.8 and TA at 50. Without occasional pucks I still need about 10-15 oz of MA weekly - or every 2 weeks. If I float a couple pucks every 2 weeks then I don't need any. I wish I kept my inline chlorinator as I don't like using a floater. In your case since you already have a floating device for other reasons I think that would work fine.

 

[ant 83]

I found this old post by Chem geek on this page: trichlor and ph

The chemical structure of Trichlor may be seen here. When dissolved in water, the three chlorine atoms attached to the ring combine with water to form hypochlorous acid where the chlorine on the ring is substituted with hydrogen from water. You can think of it this way where "CY" is the cyanuric ring core:

Cl3CY + 3H2O --> H3CY + 3HOCl
Trichlor + Water --> Cyanuric Acid + Hypochlorous Acid

So when Trichlor dissolves in water, it produces Cyanuric Acid and Hypochlorous Acid. Both Cyanuric Acid and Hypochlorous Acid are weak acids, but in the presence of a pH buffer as found in pool water the distinction between a weak and strong acid doesn't matter and the net result is that one 8-ounce 3" tablet/puck of Trichlor is equivalent in acidity as 4.6 fluid ounces of Muriatic Acid (31.45% Hydrochloric Acid).

But that is only half of the story. The Hypochlorous Acid (i.e. chlorine) does not stay around but will either get broken down by sunlight or will oxidizie an organic or ammonia. When this happens, this is an acidic process (for example, when chlorine breaks down in sunlight, it releases oxygen gas and produces hydrochloric acid; when chlorine oxidizes ammonia, it releases nitrogen gas and also produces hydrochloric acid). The chlorine that comes from that same single puck of Trichlor and then breaks down or oxidizes is equivalent to 8.0 fluid ounces of Muriatic Acid.

So the combination of Trichlor dissolving to produce Cyanuric Acid and Hypochlorous Acid plus especially the subsequent using up of the chlorine is highly acidic.

This is also why it is a myth that using bleach or chlorinating liquid will raise the pH. Though it is true that the additional addition of chlorine from such sources will raise the pH, this is almost exactly compensated with the subsequent lowering in pH when the chlorine gets used up. So looking at both chlorine addition and usage, hypochlorite sources of chlorine (bleach, chlorinating liquid, Cal-Hypo, Lithium hypochlorite) are essentially pH neutral.

Richard
​

So the simplified version is one puck is equal to about one and a half cups of 31% muriatic acid.

That doesn't sound all that complicated to me.

Trichlor pucks are cheap and store well. They also make for a convenient way to deliver chlorine to a pool as they slowly dissolve over time. The acid they deliver is can save money if it is needed.

Sometimes I think folks go overboard on negative attitudes toward pucks on this forum.

 

[Jimrahbe]

Sometimes I think folks go overboard on negative attitudes toward pucks on this forum.

ant,

As pointed out by Gene in post #2, we don't care what you put in your pool as long as you know what effect it will have. What we are against is just blindly adding anything to your pool based on "hoping" it will do something.

Nothing works better than being able to test your water and then determining what your specific pools needs, or does not need.

Thanks for posting,

Jim R.

 

[ant 83]

I'll give you an example of what I'm talking about: Getting ready for O/B Bicarbonate Startup

One new question... I bought a 35 lb bucket of pucks because it was the best "deal" per pound, but I'm wondering if that is total overkill and I should have just bought a lesser amount. I know these are helpful during startup, especially a bicarbonate startup, and I can use them to bring my CYA up gradually, but I don't know how much I will use to get to where I need it to run within SWG parameters. Even if these don't go bad, will I ever really need this many, or should I just return them and get a smaller bucket? Thanks!

So, she's got fresh water, fresh plaster, high TA, SWG, and a 35 pound bucket of pucks.

Ya'll had her lug that thirty five pound bucket back to the store, and get a smaller one at a higher (per pound) price.

A few seconds of pool math shows that in her 28000 gallon pool, 35 pounds of trichlor adds 82ppm of cya. She has a SWG, so CYA getting too high from pucks is out of the question. She should have bought a fifty pound bucket.

Buy yet, take the pucks back cause why.

Over and over again, ya'll say on fresh water to hang a sock with pure cya. Don't use pucks. Start with bleach right away. Bleach costs more. It ain't never as strong as the label says according to my testing. The stuff I'm using right now is only half strength, making the cost double. The vast majority of people start off with pucks in new water. The problems don't start until the next season (or two, or three). But doing it that way aint trouble free cause why.

 

[AftonJeeper]

In post 5 it was suggester to her by Brian to pick up some pucks for the reasons you state.

Most people come here because they are in year 3 or 4 and have a mess, or they move into a house that has a cement swamp out back. We encourage them to take control and understand what they are doing. Once people understand what they are doing I think most will understand the benefits of pucks, algaecides, and even phosphate removers.

You can't teach someone algebra until they know the basic math.

 

[ant 83]

what the original poster is suggesting isn't complicated or advanced. it makes sense and is easily understood.

but yet, their post was condemned to the purgatory that is the disagree forum.

i think that's because of an irrational dislike on tfp of trichlor pucks.

if you disagree, than we're in luck, cause you don't have to chop off my comments and move them here like you would ordinarily.

 

[BasicTek]

I did post in here because I expected this view was not going to be popular, but I still use pucks and I wish I didn't remove my inline chlorinator. Small controlled puck usage plus SWG is very TFP.

I don't think everyone holds the stance "pucks are evil" but many have been burnt using them and maybe still sore. Most of the moderators and guides on TFP maintain a more "give your pool what it needs" attitude but probably not all.

I was just shot down by a non guide for suggesting to someone that wanted to buy less than 2x SWG to compensate with puck usage and inline chlorinator on here post 4 and 6. He just didn't seem to understand using pucks to add CYA...

 

[Mayorb]

I'm not fully understanding the strife on pucks either. I have been servicing pools for 22 years. My longest current customer I have serviced for 17 years. I'm in Houston. We don't winterize. So a little basic math means I have been in my backyards about 50 times a year, and in this case would come to 850 service calls on that one pool.
I have used tabs, acid, and cal-hypo pretty much exclusively in all my pools. May be just plain lucky, but I have not once experienced any kind of tablet related problems.

I know we are all proud of our years of experience and expertise that comes with it, but let's be honest- the book on pool chemistry is far from being done written. I hate to read posts where someone emphatically states that "this is the only way to do it", or "if you do this and that, your pool will be perfect".

SWG's are great, so long as you don't think it eliminates further chemical issues, in fact you will have to a lot closer eye on your pH level. Better get ready to buy acid by the case. Travertine coping? I've seen butt prints in it where a daily swimmer would sit and read every day. Copper heat exchanger? Salt pools devour them. Metal patio furniture takes a hit too. Salt is aggressive.

I am not against salt. But for a DIY pool owner, they have to pay a lot closer attention to the chemistry than a tablet pool. As far as high Cya levels, again, I may just be lucky but I took over a salt pool 3 years ago that was a DIY previously. Unfortunately the homeowner was "shocking" his pool with stabilizer for some time before. The generator had crashed so I reverted to a floating chlorinator. I tested the Cya today, and it is still above 100 ppms. Pool looks great, never an issue.

The day we stop learning is the day we begin to fail our customers. There is no magic bullet. No one knows it all.

 

[JamesW]

SWG's are great, so long as you don't think it eliminates further chemical issues, in fact you will have to a lot closer eye on your pH level. Better get ready to buy acid by the case.

SWGs do not cause pH rise. pH rise in a SWG pool is caused by the TA being too high and the pH being too low.

At the correct TA and pH there is virtually no pH rise at all. Many SWG pools operate with no acid required all year.

Pretty much the only chemicals you need to add to a SWG pool are salt and cyanuric acid to offset salt and cyanuric acid lost to water loss other than evaporation.

If someone has high TA fill water and lots of evaporation, the constant refilling can increase TA high enough to cause pH rise.

In that case, tabs can be somewhat helpful because the chlorine in the tabs is acidic and lowers TA and pH. (The cyanuric acid in the tabs is actually cyanurate, which is a base and causes pH rise. The net effect is still acidic.)

Tabs are often misused and that’s our primary concern. Exclusive use of tabs is not practical for most pools.

 

[needsajet]

I don't buy the hate-on label. I'll bet more than half the mods and guides here have a puck or two in their pool supplies. And I'll also bet nearly 100% of them would not recommend pucks as the sanitation plan for a new build. I personally would never advise removing an inline chlorinator when switching to TFPC, unless the space was needed. bdavis gave jamiep the pros and cons and she decided entirely on her own to exchange the pucks. Yep, 35# of pucks would add 80 ppm CYA, but it would take over two months to get there, and she has an IC60 SWG on that pool.

I would love to see a pic of that butt print! That's amazing and will make for an interesting discussion!

 

[Swampwoman]

i think that's because of an irrational dislike on tfp of trichlor pucks.

There is nothing irrational about disliking something that will create a difficult and moving target for someone who wants to deploy the TFP generally bulletproof formula of maintaining a FC/CYA ratio of 7.5% (See [fc/cya][/FC/cya]

Example: CYA is the hardest test with the largest error margin and plenty of room for subjective error, eg not reading in direct sunlight.

When you add a "fixed" amount of CYA in a sock, you can cross-corroborate your reading using pool math and the change/delta.

You cannot easily track additions from pucks this way, incrementally over time.

If your goal is to dose your FC to 7.5% of CYA daily, and your CYA is a moving target, what part of this sounds like "trouble free" to you? Would you suggest daily cya readings? That would be riddiculous

TFP is intended to simplify pool care and empower pool owners simultaneously. Pucks complicate what otherwise is simple. The use of pucks, from a TFP standpoint, is "advanced" in that if you know what you're doing, yes you can use em, calculate accordingly, etc. I used to do it in the month of Oct. when I used to close. Nor would I hesitate to use pucks if needed during service to my swg, or for vaca if I weren't swg, etc.

But I would never advocate using pucks as a consistent treatment methodology inside a TFP regime because they're actually not practical at all for daily use if the goal is to honor the FC/cya ratio.

 

[Donldson]

Copper heat exchanger? Salt pools devour them.

Seriously? You seriously believe that? In your 22 years have you ever bothered to measure the salt level in one of your non-SWG customers' pools? You might be amazed just how much salt is in every single pool. Yet somehow heat exchangers only get "devoured" when it is an SWG pool? Very odd, must be special copper hungry salt I guess. :tasty:

Funny thing is the only heat exchanger I have ever seen completely destroyed happened in a pool managed with trichlor. pH bottomed out, being as trichlor is highly acidic that is no surprise. The acid ate right through the copper. The heater was barely over a year old, yet the acidic water ate right through the copper. Devoured it, if you will. Pool was never, and still isn't a salt pool.

 

[Catanzaro]

You might be amazed just how much salt is in every single pool.

Donaldson:

When I switched over from Frog System (6 months) to liquid chlorine (12.5%) for 3 years, and then converted to a SWG system, my salt level was at 1,200 ppm. The funny thing is in the beginning of 2017, I jumped in the water on a hot day and the water felt softer (little did I know this was because of the continued added salt). Yes, I always understood that salt was being added with every dosing. The nice part about this is that it only took 7 bags of salt and within 2 days I was up and running for about one month.

While a chlorinator was installed, only for convenience and because the price was right during the installation (no labor on plumbing), in addition to one day selling the property and providing the new homeowner everything they need. I have seen many pools that used 3" tablets with PH levels so low that heat exchangers that now contain metals. The salt in a pool is not what damages equipment, but it is the bad advice from pool stores, friends, etc. that people absorb over time. What truly amazes me is how someone can go out and spend $50,000 + on a new swimming pool and somehow manage to destroy the liner and heater in less than a few years, let along have rusty screws, stains all over the steps, etc., because they lack some common sense.

 

[JoyfulNoise]

It's important to remember a critical distinction here - most of the folks that post as guides, experts and mods (and ITI people) are subject matter experts (SMEs). You all know more about pools, pool water chemistry and pool equipment than 99.9% of the people posting on TFP (your "average Joe/Josephine" pool owner). This is important for two reasons -

1. You can not assume that everyone coming here will have the background knowledge and desire to understand everything as deeply as you do. Therefore, as teachers, you need to do your best to understand or ascertain the level of depth your "Student" wants to achieve and then teach to that. Sometimes that means you will omit a lot of specifics in order to get the person to understand the general ideas.

2. Many people coming here are scared/frustrated/angry/hopeless. They need moral support as much as they need intellectual support. They often need a very soft intro because they are coming from a place of either total ignorance ("I just built a pool or bought a home with a pool and I have no clue...") or fear ("I just fired the pool guy...help!"). Therefore, you often need to keep it simple in order to get them started down the right path.

So yes, that can often come off as being "anti-pucks" but it is for a good reason....people need a simple approach to start with in order for them to get their pools back into a swimmable condition and to see the value proposition of DIY pool care. There's nothing stopping someone from learning how to manage their pool in a more complicated way, eg, trichlor + SWG. phosphate removers + low FC/CYA, etc, etc. But that usually comes after years of practiced testing and dosing of their pools. This is also why I don't like seeing new people use chemical automation systems or buy into commercialized systems like Sutro, pHin, etc. - it short-circuits the in-depth learning process about one's unique pool chemistry needs.

And let's not over-generalize things - painting everyone on TFP with the brush of "you're all anti-pucks" is, to be charitable, absurd. There is more in-depth chemistry knowledge and chemical information on this forum than most 1st year college chemistry textbooks. Nothing in the written literature posted here (ie, Pool School) says that pucks are evil. Cherry-picking a few misinformed posts or bad information in the literally million-plus posts here on TFP is unfair to all of the hard work put into this site that is run for free for the world to see....so try to dial back the outrageously outrageous outrage just a tiny bit and see TFP for what it is - giving a pool owners the knowledge and management skills they need to have the very best pools possible.

 

[proavia]