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Thread: Question about sanitizing with bleach?

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    Question about sanitizing with bleach?

    Hey so I've read the chlorine threads and ive been using just dichlor up to now and I just wanted to see if i understand the switching to bleach part..

    So dichlor is chlorine+cya, and bleach is only chlorine?

    Also if my tub has an ozoator how much free chlorine should I maintain?

    And how often should I add x amount of sanitizer? (Asking because I had a problem a while back about not being about to hold chlorine but I fixed it..) Assuming 500 gal tub, use 2-3 times a WK for about 45 min.

    Thanks!
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

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    Re: Question about sanitizing with bleach?

    Did you get a proper test kit yet? If you are still using test strips, it will be much more difficult to maintain your spa properly. You've already seen how they aren't showing the CYA level properly since for every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm. Bleach does not add any CYA so is a better form of chlorine to use when you don't need to add anything else. You do want some CYA in the water since it significantly moderates chlorine's strength which would otherwise be too strong -- hence the "Dichlor-then-bleach" method.

    Dichlor is net acidic. Though it is fairly pH neutral upon addition, chlorine usage/consumption is acidic so when you switch from Dichlor to using bleach you need to set up your spa to minimize carbon dioxide outgassing. You do that by lowering the TA level (see how to Lower Total Alkalinity) to around 50 ppm and you then add 50 ppm Borates (such as by adding boric acid).

    If you didn't have an ozonator, then one person soaking for 45 minutes would need a little less than 4 teaspoons of Dichlor or 3-3/4 fluid ounces of 6% bleach (or 2-3/4 fluid ounces of 8.25% bleach). With an ozonator, you may only need half these amounts, but the real rule is to add whatever is needed after a soak so that you still measure a chlorine residual 24 hours later. As for the FC goal, most people don't want to start their soak with more than around 2 ppm FC in order to minimize noticing the chlorine since it combines with sweat fairly quickly, but that's up to you. Given the risk of getting too low in chlorine in between soaks, you might target 4 ppm FC except for the day you plan to soak where you can add less so you start with less at the start of your soak.

    The difficulty you might have is that with an ozonator the chlorine demand in between soaks may be around twice that without an ozonator. With no ozonator chlorine loss is around 25% while with an ozonator it might be 50% or even more. So an ozonator works well when you use the spa every day or two, but using the spa infrequently is more work since you have to add chlorine nearly every day when not soaking. Just see how it goes -- it's not really different than when you were using Dichlor so you may already have a feel for how often you need to add chlorine to make sure it doesn't get to zero in between soaks.

    It's too bad spa manufacturers don't have a switch to be able to turn on and off your ozonator because ideally you want to use it right after your soak for 24 hours, but turn it off in longer times between soaks if you are only soaking on weekends, for example.
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  3. Back To Top    #3

    Re: Question about sanitizing with bleach?

    Thanks for the info!

    Im still using test strips but I'm now seeing an accurate amount of stabilizer (around 100ppm+). Maybe something was wrong with my last batch of strips... I may look into purchasing a better testing kit but for now I'd like to believe what the people at my spa store tell me (not really necessary)

    With my current high amount of CYA do I need a higher FC level? I just filled it about 1-1/2 months ago so I'd prefer not to drain it to lower the CYA at this point.

    Thanks again
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

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    Mod Squad Bama Rambler's Avatar
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    Re: Question about sanitizing with bleach?

    Unfortunately you're going to have a problem if you try to combine our ways and the pool store ways. There are areas where we conflict with them and you'll get confused trying to mix the two. Our way works and it's based on hard science and is easier than the store advice. Our way is also based on accurate testing and dosing.

    You're better off picking one or the other and sticking with it. And please remember when the pool (spa) store fails you we're still here to help.
    Dave J. TFP Moderator
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    Re: Question about sanitizing with bleach?

    Quote Originally Posted by Bama Rambler
    Unfortunately you're going to have a problem if you try to combine our ways and the pool store ways. There are areas where we conflict with them and you'll get confused trying to mix the two. Our way works and it's based on hard science and is easier than the store advice. Our way is also based on accurate testing and dosing.

    You're better off picking one or the other and sticking with it. And please remember when the pool (spa) store fails you we're still here to help.
    Believe me I am totally grateful for all the help I received on here so far.

    Its just that I know a lot of people that own a spa and most if not all of them use strips over a fancy $50-70 testing kit and get along fine. Its been recommended to me numerous times but I still believe at this point in time I'm not ready to invest in one yet. Either way I understand the benefits and that strips are inaccurate but I'd rather not talk about it anymore.

    Id still like to know what I should do with the high stabilizer level I have now tho. Thanks!
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

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    Mod Squad Bama Rambler's Avatar
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    Re: Question about sanitizing with bleach?

    Drain is the only option.
    Dave J. TFP Moderator
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    Re: Question about sanitizing with bleach?

    Quote Originally Posted by spanoob9
    Its just that I know a lot of people that own a spa and most if not all of them use strips over a fancy $50-70 testing kit and get along fine.
    On another forum that was mostly about spas I kept track of hot tub itch/rash/lung reports (36 of them) as well as one incident where the person nearly died from Legionella. You are right that test strips are commonly used and it's also true that Dichlor is usually used alone so the CYA level builds up. However, it is inaccurate to say that people don't run into problems with their spas. Though many get lucky, some do not and either get infections/rashes/itch or worse and many get cloudy or smelly water they have to change more frequently.

    Test strips are generally not accurate and in particular the CYA test is the most inaccurate. This post compares the resolution, let alone the accuracy, of test strips compared to good drop-based test kits. By not even being able to measure Calcium Hardness (CH), since most test strips only measure Total Hardness (TH), you won't be able to set your CH to 120-150 ppm to reduce foaming, but not be too high as to cause calcium carbonate scaling especially in the gas heater.

    To consider how much people spend to get a pool or a spa and then to balk at getting a proper test kit and following sound scientific principles to maintaining a spa with at least twice as much time between water changes is, quite frankly, unbelievable to me. The Dichlor-then-bleach method (which includes use of a proper test kit) has been shown to provide superior water quality for a substantially longer period of time, but it's your spa and you can do whatever you want with it.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: Question about sanitizing with bleach?

    So like I said I'll consider the test kits.. That is quite alarming about the hot tub rashes I've never had anything like that other than cloudy water on occasion.

    So is a FC level like you mentioned between 2-4 ppm OK with high stabilizer? Wouldn't I have to maintain higher FC due to CYA reducing the effectiveness of chlorine?

    Side note my water is crystal clear no odor.. Not much foaming, which is why I'm hesitant about switching to bleach
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

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    Re: Question about sanitizing with bleach?

    Fortunately, bacteria are easier to kill than algae and you don't normally get algae in a covered spa, but usually one wants to keep the FC higher than around 5% of the CYA level just to play it safe so yes with 100 ppm CYA having 5 ppm FC or more would be safer. However, the problems I saw with hot tub/itch/rash were mostly due to near-zero chlorine or use of alternative disinfectants or very high CYA well above 100 ppm (usually closer to 200). There were too few of the latter cases to be definitive about an absolute problem level, but the reports that didn't have zero FC and were using chlorine had somewhere in the 100-200 ppm CYA range (most of those reports were closer to 200, but all of this is estimated based on usage and dosing -- not from CYA measurements since, remember, most people use test strips and even then most don't test CYA).

    The problem is that starting a soak with that high an FC will likely be noticeably smelly because it will combine with your sweat and form monochloramine quickly as well as other disinfection by-products you may smell. That's why most people using Dichlor-then-bleach start with 1-2 ppm FC that lessens this effect, but they have roughly 30-40 ppm CYA instead. They then dose with a lot of chlorine after the soak to handle the bather load and carry them through to the next day or two when they soak again or do a background dose of chlorine.

    The active chlorine level with 5 ppm and 100 ppm CYA or even 10 ppm FC with 200 ppm CYA will be similar to that of 2 ppm FC with 40 ppm CYA so the rate of chlorine oxidation of your swimsuit, skin and hair will be roughly the same as well direct chlorine outgassing, but the larger FC means more of it will combine with ammonia and other chemicals in your sweat and some of those chemicals are more volatile and therefore noticeable. Without an ozonator, one person-hour of soaking uses around 7 ppm FC in 350 gallons.
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  10. Back To Top    #10

    Re: Question about sanitizing with bleach?

    Sounds good thanks for the info
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

  11. Back To Top    #11

    Re: Question about sanitizing with bleach?

    Hey chem geek I had one more question.

    Been sanitizing with bleach for a few weeks now. What should my chlorine demand be? It's a 500 gal outdoor tub with ozonator, usually used 3 times a week 30/45 min soaks. I usually get up to 5 ppm FC after soaks, but then I'll check the FC in 48 hrs after no usage and it's under .5 ppm. Is that normal?

    If so should I keep adding bleach every two days when it gets to 0 even with no usage?

    Also I'm seeing like a cloudy layer of film on the water surface in the filter.
    Heres a pic I think it came out might need to zoom in to see it.


    I usually just run my skimmer through it to remove it about once a week. Just wondering if that's a sign of not enough/too much sanitizer.

    Thanks!
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

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    Re: Question about sanitizing with bleach?

    If I assume one person soaking (is that right?) for 38 minutes, then in 500 gallons with no ozonator that would be 7*(38/60)*(350/500) = 3 ppm FC chlorine demand. With an ozonator, the demand might be half that amount, so say 1.5 ppm. So the chlorine may drop from 5 to 4.5 for the bather load, but then the ozone will continue to react with chlorine and usually that is around 50% per day so from 4.5 to 2.2 ppm (I assume the first day the ozone is mostly oxidizing the bather waste rather than the chlorine). You are seeing a bigger drop than that so that sounds like your ozonator is stronger and/or is on longer.

    Yes, you need to add chlorine in between soaks so that it doesn't get to zero. You might also see if you can reduce the on-time of your ozonator, perhaps reducing circulation pump runtime if the ozonator is tied to that.

    The film on the top of the water is likely to be greases/oils such as from suntan lotion, body lotion, or skin oils. You can use a scum ball to collect those though your approach of simply cleaning them out of the filter compartment is fine as well.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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  13. Back To Top    #13

    Re: Question about sanitizing with bleach?

    Great thanks for the info! I do have different modes which control the circ pump so I'll look into those. Thanks again
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

  14. Back To Top    #14

    Re: Question about sanitizing with bleach?

    One more question I read something saying that jets should not be on when adding bleach because it causes it to be aerated.

    Should the jets be on or off when adding bleach? I just figured they should be on so it can circulate better.
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

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    Re: Question about sanitizing with bleach?

    Jets on low (if you have such a setting) are probably OK, but jets on high may splash liquid back towards your face and that is obviously very bad (if it gets into your eyes, it can blind you). The regular circulation pump is usually pretty good in a spa with fairly fast turnovers. If you have jets that aren't splashing at the surface, then having them on is OK. The idea of it outgassing to quickly isn't true when you've got CYA in the water. The chlorine will quickly bind to the CYA and the active chlorine level that outgases will be relatively low -- no worse than when you are just soaking in the spa with the jets running.
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    Re: Question about sanitizing with bleach?

    Hey I've come across this article that says bleach shouldn't be used as a sanitizer because it has no disinfecting capabilities and messes up the pH


    http://www.olympichottub.com/hot-tubs-s ... r-hot-tub/

    I'm assuming that's not completely true but Id like to hear your take on it.

    Also is generic bleach (like store brand) bleach OK or it has to be clorox?
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

  17. Back To Top    #17
    Mod Squad jblizzle's Avatar
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    Re: Question about sanitizing with bleach?

    Many members here use the Walmart or Target brands of bleach since they list the strength and have good turn over.

    Avoid any bleach that does not list the strength as it is likely very week.

    I did not read the article, but based on your summary it is completely bogus.

    EDIT: WOW that article is full of so much bad information it should be criminal.
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    Mod Squad Bama Rambler's Avatar
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    Re: Question about sanitizing with bleach?

    That article is so wrong that it isn't worth commenting on.

    The chlorine made in a chlor-alkali plant goes into bleach, trichlor, dichlor, liquid shock, and a whole host of other products. It's not different or changed because of the product. It's still chlorine.

    It's fine to use store brand bleach as long as it is plain bleach and has the percentage on the label.
    Dave J. TFP Moderator
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  19. Back To Top    #19

    Re: Question about sanitizing with bleach?

    Quote Originally Posted by jblizzle
    Many members here use the Walmart or Target brands of bleach since they list the strength and have good turn over.

    Avoid any bleach that does not list the strength as it is likely very week.

    I did not read the article, but based on your summary it is completely bogus.

    EDIT: WOW that article is full of so much bad information it should be criminal.
    When you say strength... Is that sodium hypo? The bottle says 0.25% sodium hypo (clorox says like 7.25%) but it says yields 7.5% chlorine (same as clorox)
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

  20. Back To Top    #20
    Mod Squad jblizzle's Avatar
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    Re: Question about sanitizing with bleach?

    Yes sodium hypo ... and the Clorox should say 8.25%.

    If you found bleach that says 0.25% ... that is approaching tap water
    Jason, TFP Moderator
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