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Thread: Strong Chlorine Smell - Spa

  1. #1
    Member bxcrwlly's Avatar
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    Strong Chlorine Smell - Spa

    o.k. so I used the TFP regimen to balance my water. My FC is 5.0 and stabilizer is 70. Ph is 7.5. My spa is connected to the pool via a waterfall but can be isolated for spa only mode when using it. I fired it up Friday night and and the spa started heating. Outside temp was 45 degrees. As the spa heated, as usual, it develops a vapor discharge. The smell had a very strong distinct chlorine odor. I mean really strong. I was worried about breathing this stuff while in the spa. I tested my chlorine thinking maybe I had too much CC and needed to shock the pool; however, that wasn't the case. The FC was 5.0 as noted above and the CC was 0.0.

    I never noticed this strong chlorine odor from the spa when I was keeping my FC around 3.0. Again I wanted to make sure I was following the TFP guidelines.

    Appreciate any insight. Should I be worried about the odor and breathing the fumes? It was a bit disconcerting.
    11,600 gallon plaster salt pool & spa, IC20 SWG, IntelliPH, cartridge filter, 1.5hp Whisper Flow Pump, Gas Heater, Easy Touch System w/remote, 8 roof mounted solar panels

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    Senior Member msgtdan's Avatar
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    Re: Strong Chlorine Smell - Spa

    I'm no expert especially on spas but everything I've read or heard says that if you smell chlorine it's CC's though it might not show on a test. I'm not sure if the over night loss test is valid for a spa but I think I'd try it.
    Dan D
    Used 2003 Aqua Leader 27'x52", 17,800 w/10" hopper, SwimPro SW256T 250# sand filter, Hayward PowerFlo LX pump 1hp impellor, Emerson 1 1/2 hp motor, setup Aug 2012 Summer 2011 used Summer Escapes Ring pool 14' x 42", Intex 1600gph sand filter, HTH 6 way test kitTF-100 w/stirrer, Well water @ FC=0, PH=7.2, TA=290, CH=320

  3. #3
    Senior Member DaveNJ's Avatar
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    Re: Strong Chlorine Smell - Spa

    I had noticed this on mine also. I don't think the water circulates from the spa to pool very well. Every so often I turn the valves to empty the spa into the pool, then refill with pool water. Worked for me.
    IG 18x36 oval vinyl, Spill over spa, Northstar 2hp-2spd, 2.5" piping, S310T 500lb Sand filter, 400k gas heater, AutoPilot SWCG
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  4. #4
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    Re: Strong Chlorine Smell - Spa

    This is why at least for standalone spas we recommend targeting an FC of 1-2 ppm before the start of a soak. With a CYA of 30-40 ppm, this usually limits the chlorine and chloramine odors to negligible levels and one then adds chlorine right after their soak to oxidize bather waste.

    The active chlorine level is higher at hotter temperatures at the same FC/CYA ratio. So what works well for your pool to prevent algae growth will be a higher active chlorine level in the spa. Whereas 5 ppm FC with 70 ppm CYA at 84F has an active chlorine level of 0.047 ppm, at 104F it is 0.155 ppm so around 3 times higher. Also, even more importantly, is that the lower FC will form fewer chloramines during the soak as these tend to smell more objectionable.

    So with an attached spa this will be a challenge unless you stop circulation with the pool (i.e. isolate circulation to the spa) and let the chlorine level drop (after you've heated the water up) or you intentionally lower the chlorine level in the spa before you get into it. You can use hydrogen peroxide for this purpose where an equivalent amount of 3% hydrogen peroxide will get rid of the same volume of chlorine as would be added with 6% bleach (so you can use The Pool Calculator to make that calculation).
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  5. #5
    Member bxcrwlly's Avatar
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    Re: Strong Chlorine Smell - Spa

    Chem Geek...thanks. I can and do isolate the spa. I'm curious as to your thoughts with regard to using 3% hydrogen peroxide vs. chlorine neutralizer to reduce the spa chlorine level. In either case, when I turn off the spa isolation returning to the pool "spill-over," I suspect I may need to adjust my pool FC if there is some degradation resulting from the lower FC in the spa?
    11,600 gallon plaster salt pool & spa, IC20 SWG, IntelliPH, cartridge filter, 1.5hp Whisper Flow Pump, Gas Heater, Easy Touch System w/remote, 8 roof mounted solar panels

  6. #6
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    Re: Strong Chlorine Smell - Spa

    You can use a standard chlorine neutralizer if you want to -- hydrogen peroxide is just convenient and only produces oxygen gas and chloride salt.

    The lower FC water mixing with the pool water after your soak should have a very small effect due to the huge differences in volumes of water. If your attached spa is 350 gallons, then having even no chlorine in it and diluting it back to the pool would lower 5 ppm FC down to 5*(11600-350)/11600 = 4.85 ppm FC so a loss of only 0.15 ppm FC.

    Also, your being in a spa at hot temperatures creates roughly double the chlorine demand of your being in a pool for the same amount of time and you normally don't notice the extra chlorine demand in that situation. Every person-hour of soaking in a hot spa (without an ozonator) uses around 9 grams of chlorine so in your 11,600 gallon (43911 liters) this would be 9*1000/43911 = 0.2 ppm FC so not very much.

    So between the dilution effect and your bather load, you're looking at 0.35 ppm FC to have to add to the pool.
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  7. #7
    Member bxcrwlly's Avatar
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    Re: Strong Chlorine Smell - Spa

    Chem Geek...thanks so much for the additional detail. I tried your recommendation with Hydrogen Peroxide vs. Neutralizer. The Peroxide worked really fast dropping the FC level between 1-2 within a matter of a few minutes and completely eliminated the strong chlorine odor.
    11,600 gallon plaster salt pool & spa, IC20 SWG, IntelliPH, cartridge filter, 1.5hp Whisper Flow Pump, Gas Heater, Easy Touch System w/remote, 8 roof mounted solar panels

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