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Thread: Change bromine pool to chlorine?

  1. #1
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    Change bromine pool to chlorine?

    With a 21000 gal outdoor pool in sunny position in France I was sold the idea of using bromine with an auto feeder. Useless (if I had but known of this forum first!) as impossible to keep the level high enough. So, would it be difficult to change over to chlorine using the same gear and not draining pool etc.?
    Inground Gunnite pool 30'x15' - 10mx5m
    22,500 US Gallons / 85 Cubic M.
    Hayward 3/4 hp Triton Sand Filter 220lbs - 100kg
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  2. #2
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    It's virtually impossible to change a bromine pool to a chlorine pool. Without getting overly technical, the active form of chlorine, as soon as you add it, will find the inactive form of bromine, and make it active, becoming inactive itself in the process. So basically, every time you add chlorine, you are effectively adding bromine. (I have a bromine spa, and when my bromine levels drop, I add chlorine, with no bromine content, to increase them.)

    The only way I know of is to drain the pool. Perhaps someone with more knowledge knows of some other way, but while it's easy to convert chlorine to bromine, the opposite is very hard.

    If you do try to drain the pool, make sure you read up on how to do this. It's not a simple matter at all, and draining a pool can frequently cause irreversible damage (draining a small amount off the top won't, but draining it completely can). A vinyl liner may produce a big bubble on the bottom as water flows in, permanently screwing up your pool's shape. Fiberglass pools have been known to pop out.

    In general, you're probably right that you need to switch. Bromine is generally not recommended for outdoor pools, especially in sunny areas.

  3. #3
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    Thanks for the speedy reply Matt. No problem with emptying the pool I think - as it's a concrete one that's just had a new lining applied over the old concrete. I'm wondering though, if I stayed with bromine and shocked the pool each week with a really good dose of chlorine shock if the bromine levels would stay high enough to continue using bromine....
    But I think I'm fighting against the tide here!
    Inground Gunnite pool 30'x15' - 10mx5m
    22,500 US Gallons / 85 Cubic M.
    Hayward 3/4 hp Triton Sand Filter 220lbs - 100kg
    Auto pH ColorQ Test Kit

  4. #4
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    Well, what happens is that bromine doesn't ever disappear... it becomes inactivated. It only really disappears through splashout. As soon as you add the shock, it will regenerate the bromine.

    I don't know about emptying concrete pools, but I'd get some advice before you do it if you are unsure.

  5. #5
    Senior Member MJCP's Avatar
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    My experience - so far

    I bought a home with a Bromine pool, and could not keep the Bromine levels high also.

    In fact I had many problems. I am not in a position to drain the pool and start over, but I did learn enough from this forum to follow their advice on my pool also. and SO FAR I am thrilled that this technique has worked extremely well with a bromine pool also.

    I only buy store brand chlorine (Cheapest) by the case loads!

    The following is what I "assume" is going on with my pool - I am open to any corrections by those who know more than me.

    With the old system of just the Inline Bromine feeder and 2 floating bromine feeders, the slow disolving Bromine pucks where not keeping up with the demand. I would buy Powdered shock and use the recommended quantities. I was always happy when the Bromine level actually came up enough to register on a test strip, but it would quickly drop down again, the powdered shock always left the water cloudier than before the treatment also.

    After reading many of the posts in this forum I now believe I was only "scaring" my pool not really shocking it. My new regimine is as follows.

    I SHOCK the pool with about 8 - 12 gallons of household bleach - this causes the Bromine level to jump to the highest reading on the test strip which is 10ppm. The FREE CHLORINE (FC) strip usually jumps to 5-10 ppm (Higher seems to be better). It seems to hold really well, and will turn a green swampy looking pool into a grey murky pool within an hour or two.
    During this time I filter and vacuum A LOT-. Then I force myself to be patient - and within a day everything settles to the bottom. By now the levels have probably dropped again, I add bleach (6-8 gallons) to bring the readings back to "off the charts" >10 BR >10 FC I repeat the cleaning and vaccuming (also brushing). and at this point the water looks very clear.

    Once I am at this point the Bromine feeder seems to be doing a better job and I only add about 2 gallons of bleach every other day to keep the levels in the safe swim readings. I boost it up with about 6 gallons at the beginning of the weekend, then let it go back to the "safe swim" levels 1-5ppm BR and 1-3ppm FC for the rest of the time.

    This has been working well sofar (only had the pool open a month) But I did have to go through this twice because last week it was hot and rainy, and I left town for a week with the solar cover on, I came home to green and swampy again. But it came back in 2 days to crystal clear and clean using this method.

    Again - others may modify my suggestions - take their advice (I will be)
    But this is what has been a major improvement for me over last years opening.
    15x32 Lazy L Inground / Concrete - 25,000 US Gal 1979 build
    1.5Hp/ Sand Filter, 7th season with Pool
    Painted cement finish repainted 2011
    BROMINE - (Purchased Home that way) Bleach shock
    400,000 btu Pentair Master Temp NG

  6. #6
    Administrator JasonLion's Avatar
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    Using bromine in a swimming pool is fairly similar to using bromine in a spa. There are some differences, but much of it is the same. Waterbear wrote a nice article on using bromine in a spa that probably contains some hints you could use.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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  7. #7
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    My guess is that when you are adding chlorine, it's immediately converting to bromine (hypochlorous acid + bromide -> hypobromous acid + chloride). The test for chlorine and the test for bromine are essentially identical, except that the ratio is different (you multiply the results from the chlorine scale by 2.25 to get the amount of bromine).

    If you have bromine in the pool, you cannot have chlorine. The chlorine will just oxidize the bromine and you're right back to a bromine pool. This is why people add bleach to up their bromine levels.

  8. #8
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    IF you have outdoor pools then you are losing your bromine to sunlight. Bromine cannot be stabilized against uv degredation like chlorine can with CYA. However the dimethylhydantoin used in bromine tablets does give the bromine persistance so it does not break down but gets regenerated which is why you need to drain and reill if you want to convert to chlorine. If you have never used bromine tablets but only sodium bromide and oxidizer then it is possible to convert back to chlorine without draining but you wll at least need to do some dilutions and the pool does need to get a fair amount of sunlight and a LOT of chlorine.

  9. #9
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    Re: Change bromine pool to chlorine?

    Thanks MJCP for your posting. Your situation sounds v. similar to mine, here in France. With an inground concrete pool of 21,000 G in exposed sun, it was of course stupid of me to be sold an automatic feeding bromine system - but now it's done I have to make the best of it. BUT if I now add chlorine shock AND chlorine tablets to the feeder, I'm wondering if, in time, I'd convert it to chlorine - or if not (still as bromine) would it be easier to control with the chlorine tablets, rather than with the more expensive and huge bromine needs?

    Also I suppose I couldn't convert to SWC at this point - apart from draining the pool.
    Inground Gunnite pool 30'x15' - 10mx5m
    22,500 US Gallons / 85 Cubic M.
    Hayward 3/4 hp Triton Sand Filter 220lbs - 100kg
    Auto pH ColorQ Test Kit

  10. #10
    Senior Member MJCP's Avatar
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    Re: Change bromine pool to chlorine?

    What I have found (again I'm open to any corrections from those wiser than me),
    was that trying to satisfy the Bromine demand with just the Bromine feeder was nearly impossible.
    BUT - apparently the Bromine reserve was there but "used up" Once I started using the "Bleach" as a frequent shock
    It rejuvinated all of the Bromine reserves and the Bromine levels shot up. The bleach is used up while converting the bromine. So the pool will never become a Chlorine pool this way. The bleach acts as a booster to the bromine, and the bromine levels stay much higher

    I continue to use bromine tablets in the feeder, and shock, with bleach and have had no problems Yet!
    15x32 Lazy L Inground / Concrete - 25,000 US Gal 1979 build
    1.5Hp/ Sand Filter, 7th season with Pool
    Painted cement finish repainted 2011
    BROMINE - (Purchased Home that way) Bleach shock
    400,000 btu Pentair Master Temp NG

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