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Thread: chlorine dissapation

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    chlorine dissapation

    Is there a normal amount of chlorine burn off between uses? For example assuming a CYA of 30, let's say you have a starting FC of 6...the next day with no bathers should the FC still be at 6ppm and if it's lower is that indicative of a problem?
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    Re: chlorine dissapation

    There will be loss, for sure. It just depends on how much lower your FC is. Most people have anywhere from 1.5-3.0 loss per day. Post some numbers with your home test kit and we can help!

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    Mod Squad zea3's Avatar
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    Re: chlorine dissapation

    You will have some daily FC loss until the water temperature starts to drop below 60. So many variables play into how much is normal chlorine loss on a daily basis. If you want to see if there is a problem run the overnight chlorine loss test If you see more than 1ppm loss then you have something in the water consuming chlorine.
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    Divin Dave's Avatar
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    Re: chlorine dissapation

    Hi Daveooph,
    UV from the sun will burn off some chlorine each day. How much FC loss there is to UV depends on where you are. and what your CYA level is and how much shade the pool might get. With a 30 CYA in Dallas with predominantly direct sun on the pool, I would suspect you would loose at least 3 ppm daily. Maybe even 4 in Mid August. I say this based on personal observations of my own pool.

    I'm 120 miles east of you, and I loose about 3 a day due to UV in July and August with my CYA level at 70 (I have a swg so I keep higher CYA). Less loss at cooler times of year.

    The indicators of a problem with the water, are high Combined Chlorine level (aka chloramines) of greater than .5, and / or water that just looks sort of dull.
    Either of these indicators should prompt you to do a full set of tests plus an Overnight Chlorine Loss Test to see if there are organics (algae), causing teh CCs or dull water.

    EDIT:
    Dave, just for clarification. Is your question about a hot tub or spa or a pool? The reason I ask is because I just noticed your question is posted in the Hot Tub and Spa forum.


    Quote Originally Posted by daveooph View Post
    Is there a normal amount of chlorine burn off between uses? For example assuming a CYA of 30, let's say you have a starting FC of 6...the next day with no bathers should the FC still be at 6ppm and if it's lower is that indicative of a problem?
    Divin Dave,
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    Re: chlorine dissapation

    For a hot tub if you have an ozonator the ozone will react with chlorine and will significantly increase the 24-hour chlorine demand with no bather load to 50% or more FC loss. With no ozonator in a hot spa a loss of 20-25% is more typical but if the water temperature is cooler then it could be lower.
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    Re: chlorine dissapation

    Quote Originally Posted by Divin Dave View Post
    Hi Daveooph,
    UV from the sun will burn off some chlorine each day. How much FC loss there is to UV depends on where you are. and what your CYA level is and how much shade the pool might get. With a 30 CYA in Dallas with predominantly direct sun on the pool, I would suspect you would loose at least 3 ppm daily. Maybe even 4 in Mid August. I say this based on personal observations of my own pool.

    I'm 120 miles east of you, and I loose about 3 a day due to UV in July and August with my CYA level at 70 (I have a swg so I keep higher CYA). Less loss at cooler times of year.

    The indicators of a problem with the water, are high Combined Chlorine level (aka chloramines) of greater than .5, and / or water that just looks sort of dull.
    Either of these indicators should prompt you to do a full set of tests plus an Overnight Chlorine Loss Test to see if there are organics (algae), causing teh CCs or dull water.

    EDIT:
    Dave, just for clarification. Is your question about a hot tub or spa or a pool? The reason I ask is because I just noticed your question is posted in the Hot Tub and Spa forum.
    It is for my hot tub. It also has a cover over it except when in use so I assume not much sun burn off. I think I've got something else going on cc was 1ppm.

    Build in progress: 31x18 GI (17,336 gallons) / Diamond Brite French Gray finish / Flagstone Coping / 30ft weeping wall with 7 stations plumbed / Salt Finish Deck / Pentair EasyTouch Controls / Pentair IntelliFlo Variable Speed Pump / Pentair D.E. Filter 60sft / Polaris Automatic Pool Sweep w/ Booster Pump.

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    Re: chlorine dissapation

    So brought FC up to shock level...actually higher. 16FC and three hours later with cover on and no usage I am at 9.5ppm. What do I do to get this under control ?


    Build in progress: 31x18 GI (17,336 gallons) / Diamond Brite French Gray finish / Flagstone Coping / 30ft weeping wall with 7 stations plumbed / Salt Finish Deck / Pentair EasyTouch Controls / Pentair IntelliFlo Variable Speed Pump / Pentair D.E. Filter 60sft / Polaris Automatic Pool Sweep w/ Booster Pump.

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    Re: chlorine dissapation

    How long has it been since you changed over the water?

    How are you chlorinating the spa?

    Do you have CYA in the tub? What level is it at?

    You could SLAM the tub but it might be less expensive to just do a water change. If you do drain the tub and have never done so, I would recommend using a surfactant product to flush the plumbing of biofilms. Ahh-some is the best product around for performing a deep clean of the spa plumbing. Amazon.com : Ahh-Some Hot Tub/Jetted Bath Plumbing Jet Cleaner (2 oz) : Bathroom Cleaners : Office Products
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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    Re: chlorine dissapation

    Quote Originally Posted by JVTrain View Post
    How long has it been since you changed over the water?

    How are you chlorinating the spa?

    Do you have CYA in the tub? What level is it at?

    You could SLAM the tub but it might be less expensive to just do a water change. If you do drain the tub and have never done so, I would recommend using a surfactant product to flush the plumbing of biofilms. Ahh-some is the best product around for performing a deep clean of the spa plumbing. Amazon.com : Ahh-Some Hot Tub/Jetted Bath Plumbing Jet Cleaner (2 oz) : Bathroom Cleaners : Office Products
    Just got the tub about 2 weeks ago. CYA is around 30. I ststertdd with granular chlorine and once CYA was built up I moved over to bleach.

    Build in progress: 31x18 GI (17,336 gallons) / Diamond Brite French Gray finish / Flagstone Coping / 30ft weeping wall with 7 stations plumbed / Salt Finish Deck / Pentair EasyTouch Controls / Pentair IntelliFlo Variable Speed Pump / Pentair D.E. Filter 60sft / Polaris Automatic Pool Sweep w/ Booster Pump.

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    Re: chlorine dissapation

    Ah Ok,
    Man, my bad. Disregard what I said as Im a pool guy and dont know anything about hot tub.
    Sorry for any confusion. I should have paid more attention.

    Quote Originally Posted by daveooph View Post
    It is for my hot tub. It also has a cover over it except when in use so I assume not much sun burn off. I think I've got something else going on cc was 1ppm.

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    IG Vinyl, 15' x 30', 3 1/2' - 6' deep, Oval, ~15K gal, Intelliclor IC40, Intelliflo VS pump, Clean and Clear 420 Filter, auto-fill-disabled, Retrofit LED Color Light, Dolphin Nautilus Robot, TF100 Test Kit, Taylor K1766 Salt Test Kit, Tftestkit Pressure Gauge.
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    Re: chlorine dissapation

    You didn't answer whether you had an ozonator. As I wrote, ozone reacts with chlorine so if you have a powerful ozonator you can easily lower 50% or more of the FC in 24 hours.
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    Re: chlorine dissapation

    I don't believe that I have an ozonator

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    Re: chlorine dissapation

    So maybe you got behind in dosing. The 24-hour loss rate should be measured after you've dosed sufficiently for your prior soaks so that there is not a lot of residual chlorine demand left. If you did this right, then it looks like you may have biofilm or something else consuming a lot of chlorine. A new spa has a lot of greases, oils, and sometimes biofilm from wet testing. I suggest you get Ahh-Some that JVTrain suggested and use it and then change your water.
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    Re: chlorine dissapation

    Quote Originally Posted by chem geek View Post
    So maybe you got behind in dosing. The 24-hour loss rate should be measured after you've dosed sufficiently for your prior soaks so that there is not a lot of residual chlorine demand left. If you did this right, then it looks like you may have biofilm or something else consuming a lot of chlorine. A new spa has a lot of greases, oils, and sometimes biofilm from wet testing. I suggest you get Ahh-Some that JVTrain suggested and use it and then change your water.
    Checked this morning and was at 4.5FC. Remember yestersy evening I shocked to 16 and it went down to 9 before I went to bed. I want to keep the water if possible because my fill water has a TA of over 350 and it took a lot of time and acid to get everything balanced. I'll flush with ahhsome and drain if needed though. What do you think based on this mornings FC numbers?

    Build in progress: 31x18 GI (17,336 gallons) / Diamond Brite French Gray finish / Flagstone Coping / 30ft weeping wall with 7 stations plumbed / Salt Finish Deck / Pentair EasyTouch Controls / Pentair IntelliFlo Variable Speed Pump / Pentair D.E. Filter 60sft / Polaris Automatic Pool Sweep w/ Booster Pump.

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    Re: chlorine dissapation

    You've got substantial chlorine demand. You've got 50% chlorine demand in far less than 24 hours. That's huge. There is of course a large demand when dosing right after a soak, but after the bather waste is oxidized (mostly in 12 hours, but certainly after 24 hours) the chlorine demand should get to under 25% if there is no ozonator. If the chlorine loss rate is consistent in percentage regardless of how high you start your FC level, then it sure does seem like you've got an ozonator outputting a lot of ozone. If you are absolutely positively sure you don't have an ozonator, then I really think you will need to do the Ahh-Some treatment.

    One more thing you can try is to raise the FC level, let it mix for 10 minutes, then measure it, and then turn off all pumps including the circulation pump. Then see what the chlorine demand is at that point. If you have an ozonator, it will not run when the circulation pump is off.
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    Re: chlorine dissapation

    I feel your pain, just not as severely, as my fill water is usually in the 250 ppm range for TA. But as chem geek said, you have significant chlorine demand over what would be expected. If you could post or add the details of your spa to your signature, perhaps we could determine if it has an ozonator or not. The no circulation test is also a great idea.
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    Re: chlorine dissapation

    Ok so just called the supplier and come to find out it does have an ozanator. Now what any recommendation?

    Build in progress: 31x18 GI (17,336 gallons) / Diamond Brite French Gray finish / Flagstone Coping / 30ft weeping wall with 7 stations plumbed / Salt Finish Deck / Pentair EasyTouch Controls / Pentair IntelliFlo Variable Speed Pump / Pentair D.E. Filter 60sft / Polaris Automatic Pool Sweep w/ Booster Pump.

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    Re: chlorine dissapation

    Well that makes a heck of a lot more sense. As for what to do you've got a few choices. First, ask the supplier how you can reduce the on-time for the ozonator or otherwise disconnect it. It may be tied to the circulation time in the spa in which case I'd lower that substantially. Spas turnover their water very quickly so you don't need circulation running all the time. Having it on for 15 minutes and then off for 45 should be fine, or you may even be able to go less than that. I wouldn't go more than about 2 hours without circulation and certainly not more than 4, just to make sure there aren't dead spots where bacteria could grow (they can double in population every 15-60 minutes under ideal conditions).

    Another alternative is to simply add a bunch of chlorine every day, but obviously that's extra cost and effort.

    Another alternative is to turn the spa into a bromine spa by creating a bromide bank, but you'd still probably need to cut down the on-time since the ozonator could make too much bromine.
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    Re: chlorine dissapation

    Seems like the ozanator creates more problems...why have it?

    It kicks on every time the tub pump runs. I was going to have the pump run for 2 hours every night...typically around the time we would use it. I think it automatically filters on periodically to keep temp so,there shouldn't be hours with at least a quick cycle. My understanding with bromine is that you still need some amount of chlorine. Is this the case and what advantages would bromine have?

    Build in progress: 31x18 GI (17,336 gallons) / Diamond Brite French Gray finish / Flagstone Coping / 30ft weeping wall with 7 stations plumbed / Salt Finish Deck / Pentair EasyTouch Controls / Pentair IntelliFlo Variable Speed Pump / Pentair D.E. Filter 60sft / Polaris Automatic Pool Sweep w/ Booster Pump.

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    Re: chlorine dissapation

    With a bromine spa you usually need to use chlorine once a week or so to keep the water clear, but that's mostly for spas without an ozonator. With an ozonator you may not need to use chlorine at all in a bromine spa.

    Bromine can be more expensive, but it lets you use bromine tabs in a feeder for dosing in between soaks and it can be generated from ozone. The downside is that it can be harder to control with an ozonator if on too much (i.e. the opposite problem you are having with chlorine) and technically it produces worse disinfection by-products (cytotoxic, mutagenic) though there amount is still relatively low in absolute terms.

    So you must be having your ozonator on a lot more than just 2 hours plus the "keep the water warm time". That still doesn't sound right. You should check, but it seems like your ozonator is on at least 12 hours a day unless your ozonator is exceptionally powerful.

    If the ozonator is on the appropriate amount of time for a spa, then it cuts down the amount of chorine you need to add after each soak. So for heavily used spas it can save money and also oxidizes some of the bather waste better than chlorine. So when done correctly, it can be a good thing to have.
    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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