Managing FC at Low Levels

[Gotta Pool]

Moved from HERE

72,

Prove to me it is even working... You can't, you just assume it is working..

You can test chlorine, but not UV.. Kind of the whole point of TFP...

Thanks,

Jim R.

One CAN prove if a UV light is working properly or not. The problem is homeowners don't have the tools to accomplish the task, so it just doesn't get done. The bottom line is that I suspect most UV owners just assume it is working. That logical argument, however, I think, is a red herring.

What we need to recognize, as pool owners, is that our goal is to:

Sanitize - killing microrganizms and viruses
Oxidize - organic matter such as sweat, urine, and other bodily fluids
Provide a measurable and lasting residual of the above processes.

To keep this short, I'm going to note this: Chlorine is a sanitizer AND an oxidizer. Additionally, it provides a measurable and lasting residual to continue with sanitation and oxidation. In short, it checks all of the boxes.

UV is a sanitizer and will remove chloramines, it is not an oxidizer. HOWEVER, if the UV bulb is emitting outside of the proper UV-C spectrum it will destroy ALL chlorine, which sort of defeats the whole purpose. (How do you measure this in a residential pool?) So, UV doesn't oxidize and it leaves no measurable or lasting residual and is legally considered a supplemental process to other processes, like chlorine.

IMHO, UV is best left to commercial operators who have 3-4+ water turnovers per day (less than that only treats a small portion of the water*) and the training and resources to determine the calibration and efficacy of the UV equipment. Otherwise, put in the best chlorine system you can afford, manage your chemistry properly, and enjoy the benefits of chlorine maintenance values of 4 PPM or less.

*Gage-Bidwell Law of Dilution, which see.

 

[Newdude]

One CAN prove if a UV light is working properly or not.

But what does it do for already sanitary water ?

Bupkiss. That's what.

 

[Gotta Pool]

But what does it do for already sanitary water ?

Bupkiss. That's what.

As stated, it is a supplemental sanitizer, meant to decrease the reliance on the primary sanitizer. In a commercial pool with long hours a high bather load UV might be a helpful system. However, I doubt one would ever recoup the purchase price in a residential pool.

I thought I clearly summed it up by saying, for a residential pool: in lieu of a UV system, "[one should ] ...put in the best chlorine system you can afford, manage your chemistry properly, and enjoy the benefits of chlorine maintenance values of 4 PPM or less."

 

[mknauss]

values of 4 PPM or less."

Depending on CYA levels. Many pools require higher than 4 ppm FC.

 

[Gotta Pool]

That is certainly true, but as I said, if you "put in the best chlorine system you can afford, manage your chemistry properly, [you can] enjoy the benefits of chlorine maintenance values of 4 PPM or less" without having that problem. TFP doesn't recommend that much CYA.

 

[Newdude]

enjoy the benefits of chlorine maintenance values of 4 PPM or less

While some systems may maintain the razor thin line at min FC, such as a perfectly dialed in stenner pump, cutting it that close is begging for trouble. One glitch or hiccup takes any system offline, even my beloved SWGs. In the hot climates they can lose 5 ppm a day, or 4 ppm everywhere else. If they started near min when a problem occurred, which given enough chances always occurs, it won't end well.

Just because you could, doesn't mean you should.

 

[Lake Placid]

That is certainly true, but as I said, if you "put in the best chlorine system you can afford, manage your chemistry properly, [you can] enjoy the benefits of chlorine maintenance values of 4 PPM or less" without having that problem. TFP doesn't recommend that much CYA.

So to be clear, are you advocating trying to maintain water chemistry that results in an absolute 4 ppm fc or less? The question then becomes why?

 

[Gotta Pool]

So to be clear, are you advocating trying to maintain water chemistry that results in an absolute 4 ppm fc or less? The question then becomes why?

I'm not advocating anything. I am, however, stating the scientific fact that, in an average residential pool, if the water chemistry is managed properly, there is no need for more than 4 ppm of chlorine, barring an event of exceptional bather load or an organic "accident". I think people get so caught up in how much "chlorine" they dump in that they lose sight of the fact that what is really important is the level of active HOCl.

I'm just saying, that in a world where 8.25% chlorine was $1.77 and over night 10% liquid chlorine became cheaper (per oz. of chlorine) even at nearly $10/gal. (if you could find it) I learned to be a better and more frugal pool manager.

In the context of the above thread concerning UV, I was indicating that the method of chlorine delivery can be very important and that in concert with clever pool management can banish algae, bacteria, viruses, and organics on an affordable budget. I also noted that UV is (unlike chlorine) not an oxidizer. Pool water not subjected to an oxidizer is not what I consider clean water.

If a residential pool owner wished to maintain a higher chlorine level (and many do) that is their prerogative. I merely indicate that there are options.

 

[Newdude]

there is no need for more than 4 ppm of chlorine

With peak season loss of 4ppm daily by many, that leaves no residual sanitizer. In the hot climates they may see 5ppm loss.

You need some residual sanitizer, plus the at least the recent daily loss no matter how you slice it if you wish to remain sanitary.

The alternative sanitizers all claim to be able to run a FC less than the peak season loss and that's just blatant lies. It may appear to work remaining free of algae, maybe even for an extended time, but free of algae and sanitary are two different things.

 

[Gotta Pool]

I have lived in hot climates my entire life, so I am certainly familiar with 98°F and 95% humidity. My pool water has, on occasion, flirted with triple digits. Currently, I am losing about 1.21 ppm of chlorine per day and that will probably go up some in July-August as the water temperature exceeds 90°F (it is 88°F, now.). Chlorine consumption has never exceeded 1.86, even with water in the 90's, unless we have a large pool party with kids.

Anybody losing 3, 4, or 5 ppm per day is doing so because there is something else besides climate going on (nascent algae bloom, for instance) in the pool or the water chemistry is off (pH or CYA). Alternatively, I guess it could be an extremely shallow pool like Hugh Hefner's.

Having scanned the postings of pool experts, I don't find any agreement with your statement that 4-5 ppm is a normal daily loss due to the effects of climate. Can you post any citations, not from this forum, that back up your statement ?

 

[Newdude]

Can you post any citations, not from this forum, that back up your statement ?

Just overwhelming empirical evidence reported by thousands and thousands of members spanning almost 2 decades. No two pools are the same, and any given one of them may see more or less than the norm, but we have to teach to the norm. To your experiences, we also fine tune the general recommendations to be custom tailored for that member, while not altering them for everyone else.

We're very fluid for being so rigid, but 'the basics' has to be a start point. It's usually dead on for most.

 

[mknauss]

Anybody losing 3, 4, or 5 ppm per day is doing so because there is something else besides climate going on (nascent algae bloom, for instance) in the pool or the water chemistry is off (pH or CYA).

You do not live in the desert southwest. That level of FC loss is easily achieved with the UV impact we see. North Carolina does not have the UV we have. You have clouds, and haze.

 

[Newdude]

I have run many variables on my new pool and found no diffence in loss based upon reasonable FC levels. It loses the same 3ppm right now targeting a 5 that it does at 11. Maybe it's 2.7 at 5ppm and 3 at 11, but time and time again I only saw the 3. So the start point is negligible at best, and once at a level, I'm only maintaining the same loss there. Any of us doing so accept a possible nominal increase in exchange for the freedom it provides not needing to watch it like a hawk.

I also don't see a difference at 60, 70, 80 or 90 CYA. 60 seems to be my sweet spot so I target 70 to allow some rain dilution wiggle room before I catch it being lower.

If any of the many I steer to 'run hot' came back and reported a noticeable loss increase, I'd certainly tell them to run the lower target or split the difference for a little wiggle room. So far, nobody has said otherwise and the club grows by the day.

We can in fact chalk the loss up to UV, because the breeze or the environmental crud doesn't stop when the sun goes down, but the loss does. Members prove it with OCLTs frequently. Then we double check the CYA, possibly even bumping it and then have no other variables but UV to blame.

 

[Gotta Pool]

OK, folks, this is going nowhere. You do not have any empirical evidence, you only have anecdotal evidence and opinion.

If there are no citations of scientific observation all you have is "the word on the street."

 

[SoDel]

OK, folks, this is going nowhere. You do not have any empirical evidence, you only have anecdotal evidence and opinion.

If there are no citations of scientific observation all you have is "the word on the street."

If you look at the published papers of Richard Falk, there is a ton of vetted scientific evidence showing that it is the ratio of FC to CYA and not some arbitrary FC ppm (assuming some CYA in the water) that provides adequate sanitation and provides water safe for people to swim in. He has a pretty good article that delves almost painfully deeply into that ratio, resulting HOCL concentrations, and contact times to disable various pathogens to acceptable probabilities. Don’t have a link at my fingertips but if you’re interested it should be easy to find.

The daily chlorine loss gets affected by a bunch of things but assuming a typical residential pool with adequate chlorine sanitization, solarization vs CYA level tops the list. No doubt 4 ppm FC will do the business at a given CYA level. Some places see CYA of up to 90 ppm as almost necessity due to lots of sun and many would consider 4 ppm inadequate there*. I’d humbly suggest an open mind for such things as I’ve discovered the advice here is for the most part based on very thoroughly researched and well considered science and I have been humbled a bunch of times by typing before reading .

* my memory tells me that 5% FC / CYA is a generally accepted floor although some industry advocates still argue for far lower and the level is certainly open to some empirical seat of the pants due to the wide variance in what the various factions argue to be adequate. For my money 5% is a floor and an added “safety factor” does no harm up to around I think it’s well over 20% if memory serves.

 

[proavia]

Currently, I am losing about 1.21 ppm of chlorine per day and that will probably go up some in July-August as the water temperature exceeds 90°F (it is 88°F, now.). Chlorine consumption has never exceeded 1.86, even with water in the 90's, unless we have a large pool party with kids.

How are you measuring 1.21 ppm amd 1.86 ppm of chlorine loss?

Anybody losing 3, 4, or 5 ppm per day is doing so because there is something else besides climate going on (nascent algae bloom, for instance) in the pool or the water chemistry is off (pH or CYA).

My pool easily looses 3-4 ppm of FC on a normal summer day here in Arizona - absolutely no algae and chemicals balanced). And that is with a light bather load.
What you see in NC is different from other parts of the country.

It's your pool and you are free to manage it however you wish.
You have a single data point - your personal pool - and a few "postings of pool experts" (which you fail to cite).
TFP advocates certain FC levels based on CYA level - proven by science and thousands of members experience.

 

[cwswifty]

I wonder why all of this isn’t the same color?

 

[Gotta Pool]

How are you measuring 1.21 ppm amd 1.86 ppm of chlorine loss?


My pool easily looses 3-4 ppm of FC on a normal summer day here in Arizona - absolutely no algae and chemicals balanced). And that is with a light bather load.
What you see in NC is different from other parts of the country.

It's your pool and you are free to manage it however you wish.
You have a single data point - your personal pool - and a few "postings of pool experts" (which you fail to cite).
TFP advocates certain FC levels based on CYA level - proven by science and thousands of members experience.

For those that asked: My citations would be found (among other places) in this forum and were posted by Waterbear, Chemgeek, Ben Powell, Robert Lowry, and others. This will get you started.

I measure my chlorine loss by plotting the runtime of my chlorine injector pump necessary to keep nightly chlorine as close to (but not over) 3.8 ppm and daily chlorine at no less than 2.8 ppm.

Does anybody have a clue when, how, and why the TFP position on normal chlorine loss went from 1-3 ppm to 5 ppm? Why can I not find that 5 ppm value in any other forum or media?

 

[Newdude]

Does anybody have a clue when, how, and why the TFP position on normal chlorine loss went from 1-3 ppm to 5 ppm?

It's been 2 to 4 ppm for regular season loss since I've been here AFAIK. (Time of season depending for the bulk of it). Shade, a FL style cage or low UV locations obviously lower a members loss.

5 has been reported by enough members the last few years with record breaking heat/UV, each year surpassing the last, to have gained some mention.