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Thread: OCLT with cover

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    OCLT with cover

    I have read a few places here that a cover consumes chlorine. If I have an autocover, should I leave it open overnight when doing an OCLT?
    30,000 gal IG 20x40 8ft deep end vinyl liner in NE Ohio DOB Sept 2012
    Hayward 4820 DE filter, Hayward SP2610x15 1.5HP single speed pump
    Hayward H400FDN natural gas heater, Frog min'l/Cl2 system (not in use)
    autocover, Dolphin DX4 cleaner, well water, TF100 test kit

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    Mod Squad pooldv's Avatar
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    Re: OCLT with cover

    Yes, it can. I think there are three options here:

    1 if you know how much FC your cover consumes subtract it from the number you get in the AM

    2 run the OCLT with the cover and if it is less than 1ppm you're good to go, if it is more than 1ppm try it again the next night without the cover

    3 run OCLT without the cover

    Does your cover touch your pool? If it doesn't then it will not consume chlorine. Those comments are about solar covers that sit on the water and use a little FC.
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    Re: OCLT with cover

    Our cover is a Coverstar autocover with an underguide system. The track is about 2" above the water, and the cover sits down on the surface of the water. So yes, it touches the pool.

    I was able to get <1ppm loss overnight with the cover closed. But it seemed like the pool was looking really good for a couple of days before that. So I wondered if the cover may have been contributing to FC loss. In the end, if I extended the SLAM a couple of days, that is not all bad anyway.
    30,000 gal IG 20x40 8ft deep end vinyl liner in NE Ohio DOB Sept 2012
    Hayward 4820 DE filter, Hayward SP2610x15 1.5HP single speed pump
    Hayward H400FDN natural gas heater, Frog min'l/Cl2 system (not in use)
    autocover, Dolphin DX4 cleaner, well water, TF100 test kit

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    Re: OCLT with cover

    I have an automatic electric safety cover and it's mostly opaque so if I leave it on all day my chlorine loss is around 0.7 ppm FC over 24 hours at a water temp of around 88F. Most of that loss is likely chlorine reacting with the cover. So an OCLT would still be passed if at normal chlorine levels, but at SLAM levels it's dicey. If 0.5 ppm FC over 24 hours were loss from reacting with the cover, then a SLAM has 10 times the active chlorine level so over 8 hours overnight one might have 1.7 ppm FC loss and exceed the OCLT. The fact that you had < 1 ppm FC loss at SLA< levels with the cover on means that your cover isn't consuming very much chlorine.

    So generally speaking, I would only do an OCLT at SLAM levels with the cover off.
    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"

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    Mod Squad pooldv's Avatar
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    Re: OCLT with cover

    Well, that all sounds good. Congrats on a successful SLAM! Time to
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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