SWG vs Ozonator vs UV?

[henry89056]

Topic split off from this thread Moderator

All ... brand spanking new to this forum and receiving bids from pool builders right now. This post (and others) have proven invaluable in understanding the truth in claims re. pool sanitation.

We've currently received bids from 4 pool builders who each recommend the following sanitation options: 1st) SWG and 2) Ozone/Chlorine hybrid system. Re. SWG - One of the builders specifically stated that they've seen rock/decking corrosion and damage traced back to the salt used in the SWG setup. They have begun requiring a liability waiver for SWG for this reason. In fact, there have been news stories in Dallas re. the same phenomenon. Curious if anyone can add veracity to this claim on SWGs?

Also, on another front, I am attempting to assess a possible alternative to reduce chlorine requirements but have had a hard time finding "real" information. I am curious if anyone has used / considered a hybrid UV (Spectraclear, UV254, UV Clear, BioLab UV) + chlorine system? It is easy to find many comments (here and elsewhere) that UV Systems can't work on their own - as they have no residual sanitation method. The UV companies also verify this and recommend chlorine be used in conjunction with their solution(s).

However, they also claim to be able to reduce the chlorine requirements by anywhere from 60-80%. I am wondering if pursuing a UV setup + some form of chlorination would work [while achieving a % reduction in chlorine requirements]? None of our pool builders are familiar with UV systems, so am attempting to verify this approach on my own.

Thanks again

 

[frustratedpoolmom]

Welcome, someone will be along shortly with indepth answers I'm sure, but I doubt the benefits would be worth the expense for a residential install.

Honestly, chlorine gets a bad rap, much of the problems associated with the use of chlorine are actually a result of bad water chemistry and Combined Chloramines - and result in theories that "chlorine is bad". But proper testing/water balance/maintaince techniques eliminates potential problems that could result... it's all about educating yourself - so you are definetly headed in the right direction!

I do recall reading about SWGs and certain types of stone... I'll see if I can find the thread for you and point you in that direction.

 

[Strannik]

UV does reduce chlorine demand, and so does Ozone, because it kills some things while the water passes through it, so less work for chlorine.

Whether this setup is cost effective, that's a different question.
usually they put UV/Ozone in indoor commercial pools where there are a lot of people and you can see real benefit from it.

 

[frustratedpoolmom]

OK, I found this post from one of our special contributors. It has links to two articles that the issue of stone and salt are discussed. Grab a drink, a snack and have at it, you have a lot of reading to do!

The reasons for more opposition to SWGs in Texas may relate to the discussion that started in this long thread, especially after page 10, and continued in this thread.

Richard

 

[JasonLion]

Why do you want to reduce chlorine requirements? A properly maintained chlorine pool doesn't have any of the problems that are typically attributed to chlorine. You have to have chlorine in any case (or bromine or baquacil, but chlorine is better than either of those) so there is little to gain by adding complexity and cost for little to no gain. The situation can be different in a commercial pool, where there is far more organic debris to oxidize (which both UV and ozone can help with), but in a residential pool you are already near the low end of chlorine usage and there isn't much that can be gained.

 

[henry89056]

Couple factors ... chlorine only a single factor. On the SWG, the corrosive effects of salt (perhaps due to heat in TX) have had negative (and expensive) damage attributed to it. Hence, the liability waivers many pool builders are requiring.

So, that leaves straight chlorine, or a hybrid. Chlorine has dozens of articles written as to it's carcinogenic effects. In drinking water, considered safe, but not so - at least according to these articles - in the concentration of pools. We do absorb roughly 25% of what hits our skin. Anyway, I am no expert in this regard, but I think it's wise to at least seek alternatives before settling on an entirely chlorine-based solution.

Therefor, though the SWG is still likely the easiest and most proven option for ease-of-maintenance pool-wise, I am trying to investigate ways of solving both the saline and minimize the potential harmful effects of [over] chlorination. Clearly some chlorine (or like) is required regardless of any partial-solution.

The problem is, nobody seems to actually own a UV unit to speak to its efficacy ... or lack thereof. Investment-wise, they are about the same (SWG vs. UV).

Appreciating all the feedback

 

[Strannik]

As previously said, you cannot have UV or ozonator on it's own in a pool, it won't provide adequate sanitation.

So you'll still need to have one of the 3 sanitizers which leave residual in the pool, and each of them has it's own side effects attributed to it.

 

[JasonLion]

There are a couple of kinds of stone that are known to have problems with SWGs. Why builders in Texas insist on using those specific kinds of stone always mystifies me. There are many other materials, including many other kinds of stone, that don't have problems with salt at the levels used in SWG pools.

You can't compare a SWG to a UV system, they do rather different things. A SWG system is one way to add chlorine to the water. Chlorine is both a sanitizer and an oxidizer. UV is only an oxidizer, and not a sanitizer. You can't swim safely without a sanitizer. You can compare a SWG to manually adding chlorine, or compare a UV system to an ozone system, because that pairs things which perform the same function.

Chlorine is not completely 100% safe, and neither is swimming. But chlorine (or bromine or baquacil) is thousands to millions of times safer than any alternative that doesn't include chlorine (or bromine or baquacil).

Many people on the forum have owned a UV and/or ozone system at one time or another. 90% of what we hear about those systems is that the pool owner discovers that their UV/ozone system broke months, or years, ago and they never noticed any difference.

While an ozone and/or UV system can in theory help you lower the level of chlorine you need. It doesn't work out that way in practice in a residential pool. Chlorine is consumed by three things: sunlight, sanitizing, and oxidizing. A UV or ozone system can reduce the amount of chlorine required to oxidize dramatically. But in a residential pool, the vast majority of the chlorine consumption is from sunlight, which neither UV or ozone helps reduce. Indoor pools are different, because they don't have any sunlight, and commercial pools are often different because they can have much higher bather loads, which can dramatically increase the quantity of stuff that needs to be oxidized.

 

[henry89056]

Thanks Strannik / JasonLion / frustradpoolmom ...

Yea, definitely not comparing a SWG with UV. Was more attempting to kill 2 birds with a single hybrid solution (eliminating potential salt issues and reducing chlorine). I understood that you could easily have UV / SWG working in tandem - but I wasn't crazy about the added expense of such an option (a chlorine feeder is far cheaper equipment-wise than an SWG).

This additional info is very useful for decision making. I think we are 98% likely to just stick with the proposed SWG for effectiveness and convenience sake. I am going to give a couple of the UV companies a ring just to hear their spiel, but the idea that chlorine gets consumed by the sun (I'd have to think esp. true in TX) makes a lot of sense. It's not that a UV system necessarily precludes the ability to reduce chlorine, but that other factors (sun) can work to also reduce it substantively.

I'll call them today and if anything interesting comes of it, I'll post.

 

[jdskycaster]

As with any spiel make sure you take it with a grain of "salt" (pun intented)

JD

 

[henry89056]

Quick update for those interested.

I've spoken to SpectraLight, Siemens (the water treatment engineering side) and later today I'll speak with UV254.

Bottom line is: yes, UV is a viable disinfecting solution (used all over the place for waste water treatment, etc.), but the key to effectiveness (like all disinfecting systems) is the design (fo capacity, effectiveness, lamp strength, etc.).

As a primary sanitizer, a properly setup UV system should work to minimize free chlorine requirements. It has other benefits as well.

I am still educating myself and will post a more detailed summary later.

 

[Grape Ape]

Wastewater is a very different application where the contaminating factors are on one side and the sanitized water is on the other. In a pool, the contaminating factor is floating right next to you.

Chlorine (or Bromine or Baqua) will start attacking a pathogen as soon as it hits the water, but UV and Ozone have no effect until the pathogen is sucked into the main drain or skimmer which can take hours.

I personally have had no issues with my chlorine pool. I have found other people’s private pools and commercial pools unpleasant, but I think that has a lot to do with lack of care and high bather loads respectively.

 

[JasonLion]

As a primary sanitizer, a properly setup UV system

Careful with your terminology. In the context of a swimming pool, UV is not and never can be a primary sanitizer. UV can be used as an adjunct to chlorine/bromine/baquacil (which serves as the primary sanitizer). In waste water treatment, UV can be used as a primary sanitizer, but in a swimming pool UV is used as a secondary oxidizer.

 

[henry89056]

Point taken.

I think the terms primary and secondary sanitizing agent should probably be eliminated altogether, because I think they are entirely misleading - they infer that the primary agent is a catch-all sanitizer. It would seem more accurate to say that in a hybrid system like UV / Chlorine, each contributes to the sanitary cycle. Cyrpto - for example - is far more resistant to Chlorine than to UV, in which case I think one could make the argument that UV becomes the primary sanitizer for that pathogen. In any case, it is understood that chlorine is required in the system - no manufacturer is denying that. The more specific question I am trying to answer is: can chlorine and its by-products be reduced [to safer levels] by using a hybrid system?

From the calls/emails I've exchanged in the past 2-3 days on this topic, the ability to reduce chlorine is tied directly to UV system design efficiency, which is tied to the manufacturer chosen (e.g. the chamber size/design, lamp type, effective kill rate at specific volumes, etc.) and overall circulation design of the pool. If properly implemented, Chlorine (or like) will still need to be used (in-line feeder, SWG, hand-carrying to side of pool, etc.), but there will be fewer pathogens to oxidize, thus reducing the need to keep a higher ppm of Chlorine in the pool. Which is what I'm aiming for.

Continuing to research ...

 

[Beez]

...Chlorine (or like) will still need to be used (in-line feeder, SWG, hand-carrying to side of pool, etc.), but there will be fewer pathogens to oxidize, thus reducing the need to keep a higher ppm of Chlorine in the pool. Which is what I'm aiming for.

Continuing to research ...

How do you propose to handle algae? That is another question to keep in mind, because unless you intend to use metals such as copper and/or silver or regular additions of polyquat you will need to keep a sufficient chlorine level in your water to keep the algae at bay.

If you follow the guidelines that are advocated here, your chlorine levels will already be as low as they practically can be to keep your water healthy & clear. It's pretty much one of the primary tenets of this website.

 

[teapot]

Chucking my hat into the arena:
UV is best used in bottled water manufacture, I don't agree with Jason entirely as UV of the correct spectrum interferes with the DNA of the bacteria rendering unable to reproduce so it dies off reasonably quickly. That said bacteria does not really like free swimming and prefers to attach itself to the sides of the pool and pipe work so how much actually goes through the UV chamber? Likewise algae which you will get without the correct amount of chlorine present.

UV is good at reducing chloramines so saving some of the oxidising power of the chlorine and therefore making it last longer hence the amount used is reduced. Although UV also consumes chlorine too. There is growing concern that using UV for chlorinated water use liberates a far more worrying Cyangen chloride (Mustard gas) and the effect this can have on young people to the point that several countries are looking into this problem and may ban its use. Generally this gas is afew inches above the water line right wher your nose and mouth are, only recently have gas tests been taken for analysis. I can supply some references to support these findings but just not right now.

The use of chlorine is so widespread, your tap water probably contains a similar amount as the pool and that should not concern you too much.

 

[henry89056]

Yes, the algae question has arisen from a number of people I've spoken to. UV does kill (neuter) algae, but it must be "circulated" through UV lamp in order for it to be effective. I've spoken to 2 home-owners who are running UV / Chlorine; neither of them have reported any significant algae issues with chlorine at .5 - 1ppm.

According to both, they circulate at recommended times and perform regular maintenance (e.g. scrubbing, etc.) to help ensure a portion of algae is passed through the UV cycle and ensure their chlorine is set accordingly.

 

[JasonLion]

but there will be fewer pathogens to oxidize, thus reducing the need to keep a higher ppm of Chlorine in the pool. Which is what I'm aiming for.

Even in an ideal world, where UV made a dramatic difference, which it won't in practice, you might maybe get a reduction in chlorine level of 30% or 40%, which is not going to make the pool safer in any meaningful way. What is actually far more likely to happen is that you will experiment with lower chlorine levels, use too little chlorine, allow pathogens to thrive in your water, and end up making the pool several orders of magnitude less safe.

You are worrying about the wrong things. The risks from chlorine in a properly maintained pool are minisule, almost un-measurable. The risks for problems because of low chlorine levels are dramatically higher. What you should be doing is learning how to properly maintain the pool so the big obvious problems are less likely to happen, instead of adding more complex and expensive gadgets to the pool which offer additional points of failure and new risks.

 

[henry89056]

Jason - thanks.

The risks from chlorine in a properly maintained pool are minisule, almost un-measurable.

What is this based on? I've read many articles and studies citing the links of chlorine byproducts as carcinogens. I haven't read any yet that suggest it is safe - with the exception of very generic guidelines.

Not suggesting it isn't, but would like to see evidence of it.

 

[Beez]

Yes, the algae question has arisen from a number of people I've spoken to. UV does kill (neuter) algae, but it must be "circulated" through UV lamp in order for it to be effective. I've spoken to 2 home-owners who are running UV / Chlorine; neither of them have reported any significant algae issues with chlorine at .5 - 1ppm.

That is exactly the point I was trying to make! The CYA/FC ratio that is recommended here aims at having 1ppm free chlorine as a residual. So if you follow the guidelines recommended on this site, you will maintain the same chlorine level with or without any additional system.