Can I leave pucks in my in-line chlorinator when it's off?

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marcgr

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Oct 4, 2015
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Austin, TX
I travel a lot for work and use pucks in my in-line chlor to keep the chlorine level in my pool up when I'm away.

Can I leave pucks in there with the chlorinator off when I'm at home? Or should I try to fish them out? Or just try to guesstimate the right number before I go away?

My preference would be to leave them in there with the chlorinator off...

Many thanks,

Marc
 
This is more of a guess on my part, but I'd vote not to leave them in. With it turned off they are are going to sit there and steep like a tea bag, turning the inside of the chlorinator into a very high chlorine low pH stew.

My question would be how often do you travel and do you have the CYA overhead to use tabs. I see from other posts that you have a TF-100 so you understand our methods on "How to Chlorinate Your Pool". As someone who took over a pool with extremely high CYA I guess I'm just a little hesitant to use pucks for anything other than fine tuning the CYA level.
 
Yeah, I think Tim5055 is right.

I have put them in my skimmer, pump running, but I take them out when the pump comes off.

It probably falls under one of those things that are just not good practice. A time or two wouldn't hurt much, but prolonged habits like that may damage your equipment.
 
Thanks all! Yes, I have a TF-100 (I guess I should add that to my sig!) and my CYA is only 30. Or, you could say, it's already 30 - the pool was finished in October. My pool is on a slope and has a faux infinity edge, so when it rains I get free water exchange - nothing can drain into it, but even an inch or two of rain or a splashy 6-year-old will drain water out into the slope below.

I'll take all your advice to remove the pucks from the chlorinator. Wondering if a sock would make that easier in future - is there a sock that would stand up to concentrated chlorine like that?

With the chlorinator off I've been at an FC of 3.0 for a couple of weeks and haven't added any additional chlorine. That's with sunny days in the 70's (kids were in the pool on Dec 26th!).

I do also have the UV sanitizer. I might not have bought it if I had discovered this site first, but I'll credit it with keeping my chlorine usage low. The pool builder said he'd seen examples of people with pool services that lapsed go with no chlorine for 6-8 weeks and keep clear water with UV alone. I don't plan to do that of course but I do plan to keep my free chlorine normally around 1.0-1.5 and only go up from there if it drops too fast or if the CC's creep up above 0.5.
 
marcgr said:
Thanks all! Yes, I have a TF-100 (I guess I should add that to my sig!) and my CYA is only 30. Or, you could say, it's already 30 - the pool was finished in October. My pool is on a slope and has a faux infinity edge, so when it rains I get free water exchange - nothing can drain into it, but even an inch or two of rain or a splashy 6-year-old will drain water out into the slope below.

I'll take all your advice to remove the pucks from the chlorinator. Wondering if a sock would make that easier in future - is there a sock that would stand up to concentrated chlorine like that?

With the chlorinator off I've been at an FC of 3.0 for a couple of weeks and haven't added any additional chlorine. That's with sunny days in the 70's (kids were in the pool on Dec 26th!).

I do also have the UV sanitizer. I might not have bought it if I had discovered this site first, but I'll credit it with keeping my chlorine usage low. The pool builder said he'd seen examples of people with pool services that lapsed go with no chlorine for 6-8 weeks and keep clear water with UV alone. I don't plan to do that of course but I do plan to keep my free chlorine normally around 1.0-1.5 and only go up from there if it drops too fast or if the CC's creep up above 0.5.
Click to expand...

I'm going to preface my comments with a quote from Dave, Site Owner of TFP:

Throughout TFP, you will read that we suggest certain levels that good science and practical experience has taught us fall within safe ranges.

Further reading of posts here will draw you to the inescapable conclusion that these guidelines work.......in thousands and thousands of pools worldwide.

You may or may not choose to use these methods and guidelines or you may use some and not others. Our goal is to teach you what has been proven time and time again and then let you use that information to your benefit.
Click to expand...

With that being said I don't like your plan. The biggest problem is that you are falling into a few traps -

- Mixing pool store advice/testing, or in this case the advice of the builder with TFP methods is just a recipe for disaster.

- You are already falling into the trap that UV will allow you to run lower chlorine. In our experience here with thousands of pools we have proven you can't.

- You are already planning to keep the FC dangerously low. With a CYA of 30 the FC should never go below 2 and you should target 4 so that it says above 2.

So, as Dave said we are an information resource for pool owners. How you use the information is up to you.
 
Something to consider is that one of the biggest consumers of chlorine is UV rays from the sun. Thats the main reason for adding CYA to the pool water - to protect the chlorine from consumption by UV light. You are a little spoiled right now because water temperatures are cold and there is so little UV light this time of year that the chlorine demand of your pool is probably no more than 0.2 ppm a day. If this was the middle of summer, you would likely experience a chlorine consumption of 3-4 ppm per day.

UV lights are designed to burn off combined chloramines, something that a typical outdoor pool that is exposed to the sun gets for free. The UV lights are better suited to indoor pools and covered hot tubs that need the light to burn off such byproducts of disinfection. The UV lamp in use in your pool is doing nothing more than contributing to chlorine loss and increasing your chances of falling below the minimum threshold for FC/CYA.

Pool builders know surprisingly little about pool chemistry and often times buy into the hype of product sales pitches.
 
My chlorine is dropping about 0.5ppm per week - less than 0.1ppm per day.

Right now I'm trying to do 3 turns of the water per day but mostly at a low speed on my variable pump (I have it on a higher speed when the cleaner is on). So the pump is running 12 hours per day. The UV is wired so that it's on whenever the pump is on, the UV is on. So the UV is also on 12 hours per day. We've had some sunny spells, my kids were in the pool on Dec 26th. Some leaves get blown into the pool.

If I could find some actual data to support the idea that the UV is doing anything bad, I would turn it off. However, my experience is exactly the opposite: my pool is using less chlorine than expected. I'll go one better with actual data:

I just did a little research and found that the rate of chlorine extinction in the UV-C wavelength band where the UV sanitizer operates is close to zero. Chlorine extinction is highest in the UV-A band (a component of sunlight). I direct you to the J. Chem. Phys., Vol. 120, No. 24, 22 June 2004, page 11553, Figure 5, in the paper, "Theoretical study of the UV photodissociation of Cl2 : Potentials, transition moments, extinction coefficients, and Cl*ÕCl branching ratio" http://web.chem.ucsb.edu/~devries/chem218/Cl2%20photodissociation.pdf

UV-A, which is most of what we get from the sun, is in the range from 315-400 nm.
UV-C, which my UV sanitizer generates, is in the range from 100-280 nm.

You can see from the paper that the extinction coefficient for chlorine is near zero in the UV-C wavelength band and is highest in the UV-A (sunlight) band.

I'm going to move this to a new thread as we are Waaay off topic of the original post here...
 
See THIS post for info on the UV lights.

Your lack of chlorine loss is due to the lamp being grossly undersized for the task it has been requested to do. There are many posts on the forum about UV lights and their downfalls.

3 volume turnovers is way more than needed, even in the height of summer. The pump only needs to run long enough to filter the water to your satisfaction. There are several people that during the winter run their pumps less than an hour a day, most run for around 4 hours.
 

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I am not disagreeing with you on the need to keep more than 2PPM of chlorine in the pool, thank you for teaching me that. 3 turns per day is what my PB recommended, I don't think it'll hurt anything, but you're right, I can probably back off on that.

Regarding the UV though, the main peer-reviewed academic paper on UV sanitizers that Chem Geek refers to (link) is one that I found independently, that I have read, and I have drawn a different conclusion to Chem Geek.

- When turned on for 12 hours per day, I calculated that my unit gives double the UV-C dose (fluence) that is recommended by UV disinfection regulations to produce 4 log kill of microorganisms (99.99%) in water purification applications. Link here for the 4 log kill. Actually it's way more than 4 log kill for most microorganisms. It's not undersized.
- Using the same paper that Chem Geek referred to, I calculate my loss of free chlorine to be 0.06ppm per day due to the UV unit
- My actual experience, having this UV unit on for 12 hours per day, is that my total free chlorine loss is less than what most people experience

In that other post, Chem Geek's premise against UV sanitation is that there is *some* dissociation of HOCL at the 254nm UV-C wavelength, and he's right, it is non-zero. However, it's the amount that is important, and in the very diagram that Chem Geek refers to, it clearly shows the dissociation of HOCL by UV-C is about 20% of that of UV-A that comes from the sun. There's also a *lot* more UV-A hitting the pool.

The final conclusion of that very same paper is that "The decomposition of free chlorine depends on the pH, concentration of free chlorine, fluence, and water quality. At fluence of 400 J/m2, the decomposition of free chlorine is very slight (∼1%) in DI water when the concentration of free chlorine is not very high (∼20 mg Cl/L)."

The fluence (UV dose applied to the water) of my unit, being on for 12 hours per day, is about 800-900 J/m2 (see my other post for my calculations), that being double the dose normally recommended for UV disinfection regulations. So you can't say it's undersized. At that fluence, I calculate that I'm losing 0.06ppm of chlorine per day due to the UV light, which closely matches my actual chlorine consumption of around 0.5ppm per week all things considered (sun, leaves, etc).

So:
- My unit gives double the UV-C dose (fluence) that is recommended by UV disinfection regulations
- Using the same paper that Chem Geek referred to, I calculate my loss of free chlorine to be 0.06ppm per day due to the UV unit
- My actual experience, having this UV unit on for 12 hours per day, is that my total free chlorine loss is less than what most people experience
 
If you agree that you need to run a chlorine level higher than 2, then what are you achieving with the UV light? I guess I don't really see what its doing that chlorine isn't doing on its own. The chlorine is handling all of your sanitation/disinfection and the UV from the sun is taking care of the combined chloramines. There is no benefit to running low chlorine levels either, unless the the unpleasant smell of combined chloramines is appealing.

Keep in mind that as your CYA rises from the tricolor pucks, your FC level will also need to rise to roughly 7.5% of the CYA level. The UV light will not compensate for that. Chlorine is continuously working whether the pump is running or not, the same can not be said for UV.

I think everyone's concern with the UV light is when summer comes and you are losing 3-4ppm per day from the sun, you don't want to have any extra help from your lamp (even if minimal), but again, what purpose is it serving? Chlorine loss is near-nonexistent during the colder months. Your post hit a few points that are seen time and time again with people experiencing problems: low chlorine levels, tricolor pucks (elevated CYA), and alternative sanitation (UV lamp).

For a true test, when things warm up, shut off the lamp and see what difference it makes.
 
One quick observation about fishing unused pucks out of a chlorinator is to beware of any residual gas which may be released when you open the lid of the chlorinator.

Sorry if this is really obvious advice that everyone already knows, but I had a very unpleasant blast of chlorine when opening the lid once. Ideally I'd suggest letting the residual tablets dissolve before opening.

Sent from my D6603 using Tapatalk
 
My pool is 16,000 gallons, it was finished in October and we've had ~20 inches of rain, plenty of sun, mean high temperature in November was 79 degrees, and we've had many skimmer baskets of fall leaves, plus maybe 50 person-hours of swimmers, I've been running it about 3PPM chlorine, I used enough pucks to get me to 30ppm CYA, and...

Just this week I opened my second gallon jug of chlorine.

I haven't added any chlorine of any kind in 2 weeks and the FC dropped in that time from 3 to 2, tested by the FAS-DPD test in the TF-100 (just added 20oz today to bring it back up to 3).

The UV manufacturer says that the UV system takes over some of the sanitation job from the chlorine - if the UV gets the microorganism, the chlorine doesn't have to.

So I'm thinking more about this. In a non-UV pool, how clean is the water coming out of the return jets? You're taking nicely chlorinated water and sucking it through a teabag of decomposing leaves in the skimmer basket, and another teabag of decomposing goo and bather waste in the filter (DE filters down to 3-5 micron, e.coli is 0.5x2 micron so will pass through), then returning it to the pool... in my case, right before it returns to the pool, the water gets a dose of UV-C radiation good enough to kill 99.99% of anything living within...

The chlorine is still needed for getting the remaining micro-organisms that are at large in in the pool, and for when the pump is off.

Marc
 
marcgr said:
So I'm thinking more about this. In a non-UV pool, how clean is the water coming out of the return jets? You're taking nicely chlorinated water and sucking it through a teabag of decomposing leaves in the skimmer basket, and another teabag of decomposing goo and bather waste in the filter (DE filters down to 3-5 micron, e.coli is 0.5x2 micron so will pass through), then returning it to the pool... in my case, right before it returns to the pool, the water gets a dose of UV-C radiation good enough to kill 99.99% of anything living within...

The chlorine is still needed for getting the remaining micro-organisms that are at large in in the pool, and for when the pump is off.

Marc
Click to expand...

Regardless of what the water flows through, a sufficient amount of chlorine is added to bring the entire pool volume to a level of sanitation that will inhibit/prevent the growth of organics and kill bather waste. This amount of chlorine is easily measurable, and that coupled with a CYA level can give the actual level of chlorine available for disinfection (that is not bound to CYA).

The issue I have with the UV system is how do you know its working? Can you take water samples before and after the light and measure the difference? If you could do that, what would that prove? With a sufficient amount of chlorine in the water, it really doesn't matter what else is also in the water (teabags of decomposing matter) since we are able to measure the chlorine level, and as long as that level is above 7.5% of the CYA level, then it is near impossible for anything to grow or spread (there are few exceptions, like cryptosporidium, but that would be an issue in any pool with any form of sanitation).

I looked up the literature on the Clear03, and the turnover requirements are insane. For my pool, I would need to run the pump 24/7 at nearly the maximum speed to turn 100,000 gallons in a day (3 turnovers recommended by the MFG), or have an additional UV light in place. Why not just add a sufficient amount of chlorine (regardless of the method) to kill anything in the pool?

Even with three turnovers a day, how can one be assured that every gallon of water in the pool has made it through the UV lamp? Certainly dead spots and areas of less than adequate circulation would effect this.

I understand the premise of the UV light and I can see how it could be a method of sanitation in addition to chlorine, but the light does nothing for the bather waste or organics that enter the bulk pool water prior to being run through the pump. Bathers would certainly be at risk of exposure to bacteria if the chlorine level was low (in comparison to the CYA level as the MFG recommends) since the light has done nothing for the water that has yet to pass through it.

At any rate, if UV works for you and you are happy with it, then keep doing what you are doing. You have done far more research than I have on the topic and only you can decide what is best for you and your pool.
 
I'd like to comment on what has been posted and hope that it brings some closure to the discussion. Not that I believe in using "appeals-to-authority" argumentation, but I should at least put forth that I do have significant experience with UV systems - I spent the better part of my engineering career working on and with UV lithographic system for semiconductor manufacturer as well as direct experience with high-powered UV excimer lasers, both chlorine and fluorine based UV lasers. Nothing will scare you more than having layers of skin ablated off your arm when you accidentally pass it through the open beam path of an excimer laser.

So far we have had arguments from the extremes which, while interesting, tend to fall off the mark a bit. Here's my summary and thoughts - A UV system is by no means detrimental to being added to your equipment pad and UV will kill certain pathogens that chlorine has a harder time with, BUT the systems that are designed for residential pool use suffer from both inherent weaknesses in the UV source power as well as overall design flaws that render their performance sub-optimal compared to commercial UV systems. In short, there's lot of expense incurred with the addition of a UV source for relatively little gain in water quality.

So let's look at Cost-Benefit Analysis:

Benefits

UV-C light, also known as UV Germicidal Irradiation (280-200nm, with 260nm being the optimal wavelength), does effectively kill a whole host of bacterial pathogens that chlorine either has a hard time with or can not kill at all (ex, protozoan oocysts). While UV-A and UV-B light come from the sun and hit a pools surface, very little UV-C makes it through the atmosphere due to the ozone layer absorbing it. UV-C light will also kill algae (planktonic, or free floating, algae) but so too does chlorine. UV light does not, on it's own, generate disinfection by-products like combined chloramines; it simply inactivates or kills the pathogen which degrades its ability to reproduce.

Costs

Standard online pricing search yields that a Paramount UltraUV system can range from ~$490 for a 230V, 1-lamp unit and up to ~$730 for a 230V, 3-lamp unit. I have not found any 4-lamp units online even though the manufacturers user manual claims that 4 lamps is the max number for these systems. Each lamp has a replacement cost of ~$100 per lamp. I have yet to find pricing for the exact replacement model of the fused quarts inner tube, but a check of cached on-line sales pages shows the 2-3/8" x 21" tube replacement assembly to be ~$75. While lamps are rated for a 13,000hr lifetime (continuous use), most recommendations seem to point to a 2-yr replacement schedule for the bulbs and no scheduled replacement for the quartz tube outside of physical damage. So, if one had a 3-lamp unit, the replacement cost of the lamps would exceed the system cost within 4 years. None of this assumes any plumbing reconfiguration that might have to occur if this unit is added to an existing pool as opposed to installed upfront with the pool equipment.

System Limitation

While we can all argue in the abstract about a "perfect" system, one must take into account the inherent design flaws of these UV disinfection systems. I will simply list a few here without going into great detail and this should not be considered an exhaustive list -

1. Volume treated/turnover rates - because of the low internal volume of the treatment tank and the fact that water is flowing through it at a considerable rate, a long treatment time is necessary. Assuming a pool pump operates at 50GPM and the internal volume of the UV tank is 15 gals, the water only resides inside the unit for about 18 secs. Because of these volume differences, the operating instructions specify the use of large turnover rates of pool water to ensure that as much of the pool volume as possible gets treated. This means one must run their pumps longer and at lower speeds to improve the efficiency of the UV treatment. Also, without overstating the obvious, only planktonic pathogens (free floating algae and bacteria) are treated by these methods.

2. No Residual Disinfection - I think this states the obvious, but once water exits the UV system, there is no "residual" disinfection. Any pathogen that might have made it through the tank without being inactivated is now free to go on it's way.

2. Bulb Output - The UV bulb types used here are low pressure mercury vapor lamps that typically operate around 60W or so electrical power. While this type of lamp is efficient at producing UV-C light, the power densities are fairly low (1 W/cm). No bulb will operate perfectly over it's lifetime and so, as the bulb ages, it's UV-C output will diminish with time. Mercury lamps should never be discarded in general trash but sent back to manufacturer for proper disposal as mercury is both a human and environmental hazard.

3. Quartz tube housing - The quartz tube that houses the lamp will, over time, build up scale on the surface that is in contact with the water as well as develop what are known as "color-centers" in the volume of the fused quarts. These color-centers are caused by the UV irradiation damaging the crystalline structure of the quartz which cause greater absorption over time, in effect, reducing the ability of the quarts tube to transmit UV light. Routine cleaning of the quartz tube surface is a must to ensure proper operation of the unit and replacement is required should the tube become frosted or damaged.

4. Water quality - The water in our pools is not pure. It contains plenty of dissolved solids, particulates and chemicals that will enhance the absorption of UV light and scatter it thus reducing the efficiency of the UV germicidal action. Hypochlorous acid does, in fact, react with UV-C light but not to an extent to cause significant chlorine demand. However, any UV light that converts hypochlorous acid to chloride is lost to disinfection of pathogens.

In current practices, UV disinfection finds it's most efficient use in drinking water treatment. We have at least a few TFP members who work in the water treatment industry so they can certainly respond better. However, in that context, UV disinfection systems are typically deployed inside surge-tanks that hold 10,000-15,000 gallons of water at a single time and the UV sources are allowed to operate for longer periods of time on those volumes. UV systems are also used in conjunction with Ozone & Peroxide treatment tanks (referred to as peroxone in the industry) to act as another layer of disinfection. Once again, these are static volumes of water that are fully treated before entering a closed loop distribution system; this is a far cry from the way residential pools operate. Anyone interested in reading more about this can look up the term "Advanced Oxidation Processes" on the internet.

Finally, let's put a lot of this into context. For the standard residential, low bather-load pools, the biggest nuisance by far is algae. Algae is not considered a human pathogen (it's exceedingly difficult to get algal infections in the human body), it is a nuisance. Yes, there are some bacteria and other pathogens that can inhabit algae and use them as a disease vector, but those instances are rare. What is also quite rare is bacterial loads in residential pools. While we all sometimes think that our pools are the breeding grounds for the next Black Plague outbreak, the simple truth is that most residential pools (when properly chlorinated) are quite free of any significant bacterial loads. Also, the really nasty bacteria and parasites that keeps us up at night (p. legionella, cryptosporidium, giardia, etc) are just not that common is a properly chlorinated swimming pool. UV systems used in the context of swimming pools find their most efficient use in high bather-load public/commercial pools where the risk of disease transmission via person-to-person contact is much greater. If I swim with my kids in our pool, there is no pathogen from them that I am not already exposed to on an on-going basis. If I jump in the public pool at the local YMCA, I am basically swimming with dozens, if not hundreds, of people that I do not know and who can easily expose me to the diseases they may be carriers of.

Well, that was a really exhausting post to write. Hopefully anyone reading it will take it for what it is - I am neither strongly for or against UV systems. I think they have a lousy cost/benefit ratio but others may put a higher price on adding layers of protection. I feel that their marginal increase in pool water sanitation is fully offset by their up-front and recurring financial costs.

Best wishes,

Matt
 
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Hi Matt,

Thanks for your reply, well balanced.

On the power output, mine is rated at 30mW/cm2 - but that is plenty. 30mW/cm2=300W/m2 (Source: http://codypools.com/owners/sanitation/Paramount%20Ultra%20UV.pdf )

The fluence required for 4-log kill of almost everything is 400J/m2 remembering that 1J=1W*1s. In other words, 1.3 seconds in the UV chamber is enough to kill 99.99% of everything living in that water. Source: https://www.unesco-ihe.org/sites/default/files/3_-_templeton.pdf , page 6.

Thanks,

Marc
 
marcgr said:
Hi Matt,

Thanks for your reply, well balanced.

On the power output, mine is rated at 30mW/cm2 - but that is plenty. 30mW/cm2=300W/m2 (Source: http://codypools.com/owners/sanitation/Paramount%20Ultra%20UV.pdf )

The fluence required for 4-log kill of almost everything is 400J/m2 remembering that 1J=1W*1s. In other words, 1.3 seconds in the UV chamber is enough to kill 99.99% of everything living in that water. Source: https://www.unesco-ihe.org/sites/default/files/3_-_templeton.pdf , page 6.

Thanks,

Marc
Click to expand...

Marc,

Thanks. Though the manufacturer's instructions say the unit has an output of 30mW/cm^2, they don't say if that is for 1 bulb or 4 bulbs? Any idea on who manufactures the bulbs or part numbers for them? GE and Ushio are the two major manufacturers of germicidal UV lighting (and UV lights in general) so it would be interesting to see what the actual spec sheets for the bulbs say. I only ask because it seems that replacement bulbs are hard to come by except, perhaps, through Paramount themselves and there is not a lot product info on them.

Also, while I appreciate the Imperial College presentation, it's always preferable to operate from literature with actual peer reviewed data in it. You will find this EPA Document much more comprehensive - UV Light Disinfection Technology In Drinking Water Application - An Overview. It's a bit dated, but the more recent EPA studies have been moved off their original links for server updates, so the newer studies have to actually be ordered for cost.

Please let us know how your UV system works over time. It would be interesting to see if you can detect a change in chlorine usage with and without the UV system in use.

Best wishes,
Matt
 

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