Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 9 of 9

Thread: Why is everyone anti-UV?

  1. Back To Top    #1

    Join Date
    Apr 2016
    Location
    Round Rock/TX
    Posts
    2

    Why is everyone anti-UV?

    We have been talking to different contractors about a pool. We are located in Round Rock Texas (suburb of Austin). Every single contractor has warned us of the corroding effects (on surface, filter, everything) of saltwater and recommend either UV or plain chlorine. Then I jump on this forum and see nothing but saltwater recommended. Confused. Can someone explain this?

  2. Back To Top    #2
    Mod Squad kimkats's Avatar
    Join Date
    Jul 2012
    Location
    Tallahassee, FL
    Posts
    26,737

    Re: Why is everyone anti-UV?

    Here at TFP we are all about knowing the hows and whys. Please read this:

    Alternative sanitizers and pools--The Truth!!

    If you have any more questions or just want to chat about your new pool PLEASE feel free to ask!

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

  3. Back To Top    #3

    Join Date
    Apr 2013
    Location
    Sacramento, CA
    Posts
    2,769

    Re: Why is everyone anti-UV?

    Certain locations have problems with salt crosion. Austin is one such location. But the vast majority of pool owners have little or no problems. There are threads on here right now about problems with salt in Austin. But those are problems with natural stone not pool systems.

    A salt pool is a chlorine pool, it just manufactures the chlorine in the pool from the salt.

    A UV pool is a chlorine pool. It must maintain a certain level of chlorine in the pool to sanitize the pool ( kill the bad stuff).
    All the UV does is oxidize (burn off --break down) the dead bad stuff or chemical debris of sanitation.

    This forum generally recommends using chlorine as a sanitizer and oxidizer. But there are a number of ways to get there. Salt is not the only automated way. A Stenner pump is almost as maintainance free as a salt system and has a lower initial cost.

    We generally don't recommend UV systems for outdoor residential pools because chlorine and sunlight render them redundant. Indoor pools or public pools -- yes. Outdoor residential pools will see little if any effect from UV. Another way to put it is that by maintaining the pool with adequate chlorine sanitation(which you have to do with UV) then the combination of sunlight and chlorine will provide the same oxidation as a UV system
    22k gallon IG pebblefina, Jandy 1.5 HP VS, Jandy CV Cartridge filter, Fafco solar panels, Polaris 360 supply side cleaner, waterfall

  4. Back To Top    #4

    Join Date
    Oct 2015
    Location
    Austin, TX
    Posts
    83

    Re: Why is everyone anti-UV?

    I heard the "no saltwater" enough not to install one. I do believe the corrosion from a SWG is bad enough that the poolbuilders don't want to warranty the decking, the question I don't really know is whether the corrosion is too bad for my standard...

    I'm running a 30-40 CYA and a 3-5 range of FC, a little borate, and balanced TA and CH and my pool water is as sweet as you can imagine. People ask me if it's a saltwater pool and I say, "no, it's just well managed".

    The problem with Stenners and other chlorine dosing systems here in Austin is that there isn't a HASA or other bulk chlorine provider, so you've got to buy jugs of chlorine bleach a gallon at a time from HEB... so get ready for that whether you have a Stenner or not.

    As for the UV unit, I have one and I did the research. I see a lot of people on this forum equating the UV from the sun with the UV from the UV unit which isn't correct because they're different wavelengths. The wavelength of the light from the UV unit is tuned to a wavelength that disrupts cells (bacteria and algae) much more than the UV from the sunlight, so the UV unit will kill stuff that the sunlight won't. However, with the exception of some hard-to-kill bacteria that UV is particularly good at killing, the chlorine will kill the same stuff that the UV unit does. And the UV unit only treats the water that's in the UV unit at that moment.

    The UV unit isn't a substitute for chlorine, and the UV unit isn't necessary. You still need to maintain the same level of chlorine in the pool to maintain sanitation for all the pool water that isn't going through the UV unit at that moment. I'm happy enough with mine, and I will note that my chlorine usage seems to be less than what others without UV units report, about a cup a day on average in a 16,000 gallon pool, I've never detected CC's more than 0.5ppm, but I haven't been through a full summer yet.
    Pool: 16,000 gallons, 16x31, 500SqFt gunite pool, White Pebbletec interior, built by Cody Pools. Pentair Intelliflo VS-3050 pump, Pentair Clean & Clear 420 Cartridge Filter, In-line chlor with Ultra UV, PV3 Infloor cleaning, Pentair Easytouch-P4 control. TF-100
    Spa: 525 Gallons, Coast fiberglass spa of unknown vintage and suspect previous care with a 2-speed main pump and a blower motor, both 4HP. 3-step bromine sanitized.

  5. Back To Top    #5

    Join Date
    Dec 2014
    Location
    Cypress, Texas
    Posts
    200

    Re: Why is everyone anti-UV?

    Quote Originally Posted by marcgr View Post

    The UV unit isn't a substitute for chlorine, and the UV unit isn't necessary. You still need to maintain the same level of chlorine in the pool to maintain sanitation for all the pool water that isn't going through the UV unit at that moment. I'm happy enough with mine, and I will note that my chlorine usage seems to be less than what others without UV units report, about a cup a day on average in a 16,000 gallon pool, I've never detected CC's more than 0.5ppm, but I haven't been through a full summer yet.
    We didn't get a UV system, but asked about it and that's what we were told, that its supplemental to Chlorine and it helps reduce Chlorine usage?
    2016 Build: 32x8 Gunite, 6,700 gallon IG pool including 6x8 spa and 6x8 tanning ledge w/ 2 bubblers. 32' raised wall with two sheer descent water features. Travertine Coping w/ split faced Travertine on raised wall face. 2HP VS Jandy pump, 400k heater, Rainbow Chlorinator, 4 Colored LED Lights. 459sqft spray deck plus. IAqualink remote, Polarus 9350 Robot Cleaner.

  6. Back To Top    #6
    JoyfulNoise's Avatar
    Join Date
    May 2015
    Location
    Tucson, AZ
    Posts
    11,629

    Re: Why is everyone anti-UV?

    As gwegan posted, it seems that the Austin-area pool builders are pretty much dead set against salt pools in so far as they don't want to warranty against any kind of salt water damage to pool decking, stone work, etc. I think I live in an area of the country that is quite a bit more harsh in terms of environmental stress than Austin and yet my stone work looks fine and I have a salt pool. So, whatever the local conditions are in Austin, you will simply just find it difficult to get a PB to build you a salt pool.

    But let me be clear about pools - short of operating a Natural Swimming Pool (NSPs use no chlorine and rely solely on coagulation, filtration and biological control), any pool will eventually become a salt water pool if there is low fresh water exchange. Liquid chlorine, cal-hypo, stabilized chlorine (dichlor, trichlor) and muriatic acid ALL add chloride to your water. It is not uncommon for people to report here that they have pool water with a chloride build up of over 1000ppm/year simply from using chlorinating compounds. So, any pool builder that thinks they are mitigating salt exposure by not offering SWG's is just delaying the inevitable (of course, they will blame any damage on the pool owner's negligence in keeping the water balanced to APSP standards). In areas with high rainfall and a good balance between rainfall and evaporation, chloride build up will be low....but, then again, salt damage would be minimal as well due to rain washing away salt from decking and stone work.

    As for UV systems, well I've written at length about them. They are alternative sanitizers that, in my opinion, have a lousy cost-benefit analysis. You can certainly install one and admire the placebo effect, but there is little direct evidence that they make any difference in terms of chlorine use. Anyone can easily experiment with this and use a UV system for a season, keep good records of their chlorine use and then, the following season, simply unplug the unit and see what happens...
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

  7. Back To Top    #7

    Join Date
    Aug 2014
    Location
    Austin, TX
    Posts
    74

    Re: Why is everyone anti-UV?

    My PB highly recommended a UV system as a supplement to chlorine and used the argument that it kills things chlorine will not and will help lower your overall chlorine consumption. I cannot attest to the fact that any of that is true after 8mos of owning and enjoying the pool, but I can give this advice....

    If you have a spa and your sitting in the spa with 5 other adults one night and thinking (as I have done) how quickly the chlorine in that little spa just got used up, you will be glad you have that spa water running through the UV sanitizer!
    12300gal IG PebbleTec w/7' raised Spa & Waterfall. Built Aug 2015
    Pentair IntelliFlo VS Pump, Pentair 420 Cartridge Filter, Ultra UV, Auto Fill
    EasyTouch control w/ Remote, Infloor Cleaner w/1.5HP Pump and Leaf Canister
    Stenner 45MPHP10 w/15gal tank, Rainbow 320 Chlorinator, TF-100 Test Kit.

  8. Back To Top    #8
    JoyfulNoise's Avatar
    Join Date
    May 2015
    Location
    Tucson, AZ
    Posts
    11,629

    Why is everyone anti-UV?

    Yes, but one must realize that a spa is not a pool and a pool is not a spa. They are two completely different bodies of water (regardless of whether or not they are connected to the same plumbing), each with their own, very different requirements.

    A spa is a much smaller volume of water that has a far higher bather-load as compared to a pool. To demonstrate that point, a rough rule of thumb is that a pool requires about 4 grams of chlorine per person-hour of bather load. In a 15,000 gallon pool that would equate to ~0.07ppm FC. A 400 gal hot tub, by contrast, requires about 3.5fl oz of 8.25% bleach per person-hour of bather load OR almost 6ppm FC. A UV lamp or ozonator on the spa can cut that FC requirement by as much as half but it is still a lot higher than a pool. As well, a spa circulation system will turn over water at a much higher rate than a pool pumping system such that the spa water has far greater contact time with the secondary sanitizer.

    The point is this - UV sources were originally developed for spas and indoor pools that absolutely needed secondary disinfection sources to handle the complex bather load problems associated with them. The pool industry took the concept and tried to add it on to the equipment pad of outdoor residential pool with little thought to its effectiveness. Outdoor residential pools get more than enough UV-A and UV-B light to help eliminate CCs. The amount of additional UV light (germicidal UV-C) added to the system is fairly insignificant when one considers the oxidation of organic compounds.

    And yes there are bacteria and other pathogens that chlorine has a hard time killing BUT the bacterial loads in residential swimming pools are exceedingly low and the instances of finding those hard-to-kill pathogen in a residential pool even lower still. So the actual benefit of being able to kill those types of pathogens is rarely, if ever, experienced by the typical pool owner.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

  9. Back To Top    #9
    Isaac-1's Avatar
    Join Date
    May 2010
    Location
    SW Louisiana
    Posts
    6,711

    Re: Why is everyone anti-UV?

    I think JoyfulNoise has summed this up nicely. We are not against the use of UV or Ozone systems, we just feel that they are of little or no benefit in the typical residential pool, as to the issue of reducing Chlorine use, the simple truth is it depends, with high bather loads, yes it can, but with typical residential bather loads in a well balanced pool it often increases Chlorine use.

    Think about it this way, Chlorine sanitizes and oxidizes bather waste, then UV light from the sun breaks down the Chlorine. This UV from sunlight breakdown of Chlorine is what eliminates the combined Chlorine compounds from your pool (the bad stuff), it also breaks down the Free Chlorine ( the good stuff). A UV systems kills pathogens by exposing them to a wide spectrum of UV including UV-C which in nature is almost entirely blocked by our atmosphere (That Ozone layer thing), so while these UV systems do kill pathogens taking some of the work load off your Chlorine as the water passes through UV cell, it also breaks down your Chlorine. The question then becomes does it break down more or less Chlorine than would be consumed breaking down the organic compounds in your pool. In the studies from the UV sales brochure they try to convince you that it does more help than harm, however they are often starting from a pool that may have algae issues and is not properly Chlorinated, in the real world dealing with a well balanced pool the benefits become a lot more questionable.

    Also while there are some pathogens that UV can eliminate nearly instantly which may take Chlorine many hours to break down, these UV systems can only kill the pathogens that passes through the UV cell, so only applies to pathogens that are free floating in the water, not clinging to some pool surface, and it takes many days for the typical pool pass nearly 100% of its water through the filtration and UV system. Even if we take the common industry standard practice of sizing pumps to filter 100% of the water every 8-12 hours, it is not like we have a full pool and an empty pool to move water between, so in that pretend 12 hour water turn over time only a fraction of the water will pass through the UV cell, another smaller fraction will pass through twice, and other smaller amount 3 times, and so forth. There is math to back this up, but lets leave it at it takes a couple of days or more for 99% of your water to pass through the UV cell, and much longer for 99.9 % or 99.99%.... by that time the Chlorine would likely have had its many hours needed to kill the pathogen.
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
    I use and endorse TFtestKits TF-100 from http://tftestkits.net
    ~Remember TFP counts on your donations to keep this site ad free~

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •