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Thread: OCLT during the daytime, and bleach drip feeder wasteful ?

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    OCLT during the daytime, and bleach drip feeder wasteful ?

    Looking for input on 2 items that I have been pondering on.

    OCLT during the daytime.

    If my understanding is correct, the main purpose of the OCLT is to determine if an algae problem exists. I fully understand the reasoning for doing the test overnight to rule out sunlight that destroys the chlorine.

    But lets assume that the pool owner has at least brushed the walls of the pool, and ( here I am assuming ) that if there was algae in the plumbing or filter, it would also most certainly also be in the water.

    So what's to stop me from doing a 6 or 8 hour daytime test, by filling a clean bucket with 10 liters pool water, measuring the chlorine, and then putting the bucket away in a dark room ? Would this not server the same purpose as doing the test overnight ?


    Bleach Drip Feeders

    I have read a few threads on the forum about using irrigation drippers for a slow supply of bleach to provide the basic pool chlorine requirement.

    However, wouldn't these drippers supply a constant ( yes, very slow ) supply ? I don't see the point in this.

    In my pool, under a very hot sun for many hours a day, the FC drops from, lets say, 4 ppm in the morning to just under 2 ppm by late afternoon. After the pool is in the shade, I calculate the cal-hypo required and add to the weir.

    So if I was to use a system that fed a very slow continuous supply, surely most of it would be partially wasted because it would be added to the water during sunny hours.

    Or is it not a concern because the drippers only feed if the pump is running and most users run their pumps only after sunset ?

    Personally, I run for 4 hours in the morning after sunrise to get the solar coils to heat the water, and then again 4 to 6 hours after the sun is down for the newly added chlorine to work.
    Fiberglass lined pool 37,000 liters ( 9775 US gal ), In-ground. Outdoors.
    Equipment : Speck 0,75 kW pump, 2 bag sand filter, Cartridge filter ( large 90,000 liter ( 23,775 US gal ) capacity ).
    T-Piece split with 2 ball valves - 1 to the pool return inlet, other to a 7 coil solar system on flat carport roof ( total area 11.49 sq.meters - 55 sq.ft ), and that to a second return inlet. Each inlet gets about equal flow, but can be adjusted using ball valves.
    Pool temperature 24 Celcius ( 75 F ) in winter, 32 celcius ( 90 F ) in summer.

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    Mod Squad Bama Rambler's Avatar
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    Re: OCLT during the daytime, and bleach drip feeder wasteful

    1) Theoretically it would work, but in practice it isn't very accurate as the bucket may or may not have organics that the pool has. If the algae is hiding in the pool light, for instance, then unless you dipped the bucket right in front of the light and got some of the algae in the bucket you'd pass the test in the bucket, but you'd fail the test in the pool. You can have algae and it not be all throughout the bulk pool water.

    2) If your pool uses 2 ppm FC per day, it doesn't matter when you add the 2 ppm FC to it. Adding it during the daylight or in darkness makes no difference in how much of it gets destroyed.
    Dave J. TFP Moderator
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    Re: OCLT during the daytime, and bleach drip feeder wasteful

    Quote Originally Posted by Bama Rambler
    1)You can have algae and it not be all throughout the bulk pool water.

    2) If your pool uses 2 ppm FC per day, it doesn't matter when you add the 2 ppm FC to it. Adding it during the daylight or in darkness makes no difference in how much of it gets destroyed.

    OK. Great. I fully get the point about the bucket test and agree with your comments. Thanks.

    About the 2 ppm added - if it is added during the daytime, wouldn't it be less effective as some of it would also be destroyed by the sunlight ? So out of the 2 ppm, lets say 1.5 ppm does some work in the water, but 0.5 ppm is destroyed. Adding in the evening means that all of the 2 ppm gets to work in the water ? Or do I misunderstand the reaction / process ?
    Fiberglass lined pool 37,000 liters ( 9775 US gal ), In-ground. Outdoors.
    Equipment : Speck 0,75 kW pump, 2 bag sand filter, Cartridge filter ( large 90,000 liter ( 23,775 US gal ) capacity ).
    T-Piece split with 2 ball valves - 1 to the pool return inlet, other to a 7 coil solar system on flat carport roof ( total area 11.49 sq.meters - 55 sq.ft ), and that to a second return inlet. Each inlet gets about equal flow, but can be adjusted using ball valves.
    Pool temperature 24 Celcius ( 75 F ) in winter, 32 celcius ( 90 F ) in summer.

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    Mod Squad Bama Rambler's Avatar
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    Re: OCLT during the daytime, and bleach drip feeder wasteful

    You're just over thinking it a little. The recommeded level suggested here is all that you need to keep the pool sanitary. Having more really doesn't do anything. The only reason you need more FC is to account for the daily loss. So while adding it during the dark sounds good, it's really just sitting there doing nothing until the sun comes up the next day.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Re: OCLT during the daytime, and bleach drip feeder wasteful

    Quote Originally Posted by Bama Rambler
    You're just over thinking it a little. The recommeded level suggested here is all that you need to keep the pool sanitary. Having more really doesn't do anything. The only reason you need more FC is to account for the daily loss. So while adding it during the dark sounds good, it's really just sitting there doing nothing until the sun comes up the next day.
    That's the first time I've read it takes sunlight for chlorine to fight algae. Since it doesn't take long to distribute chlorine ( I've read 30 minutes somewhere), adding it after sundown, or just before is the most effective time to do it without the sun burning it up.
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    Re: OCLT during the daytime, and bleach drip feeder wasteful

    Quote Originally Posted by timerguy
    Quote Originally Posted by Bama Rambler
    You're just over thinking it a little. The recommeded level suggested here is all that you need to keep the pool sanitary. Having more really doesn't do anything. The only reason you need more FC is to account for the daily loss. So while adding it during the dark sounds good, it's really just sitting there doing nothing until the sun comes up the next day.
    That's the first time I've read it takes sunlight for chlorine to fight algae. Since it doesn't take long to distribute chlorine ( I've read 30 minutes somewhere), adding it after sundown, or just before is the most effective time to do it without the sun burning it up.
    Having re-read Bama Ramblers post, I think that what he is referring to, when saying it's just 'sitting around', is the excess FC over and above the FC that is required to keep the water sanitary. So if the 'required' ( minimum ) FC ( for a given CYA level ) is, lets say, 2.8ppm and the 'recommended' FC is 4.5ppm, then the FC above the 2.8ppm is just going to sit there until the next day - assuming of course that the required FC of 2.8ppm is sufficient to sanitize the water and the excess is not used thereafter.

    Just assuming here, so am sure Bama Ramblers will likely clarify what he meant with the statement.
    Fiberglass lined pool 37,000 liters ( 9775 US gal ), In-ground. Outdoors.
    Equipment : Speck 0,75 kW pump, 2 bag sand filter, Cartridge filter ( large 90,000 liter ( 23,775 US gal ) capacity ).
    T-Piece split with 2 ball valves - 1 to the pool return inlet, other to a 7 coil solar system on flat carport roof ( total area 11.49 sq.meters - 55 sq.ft ), and that to a second return inlet. Each inlet gets about equal flow, but can be adjusted using ball valves.
    Pool temperature 24 Celcius ( 75 F ) in winter, 32 celcius ( 90 F ) in summer.

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    Re: OCLT during the daytime, and bleach drip feeder wasteful

    Quote Originally Posted by Bama Rambler
    ...it's really just sitting there doing nothing until the sun comes up the next day.
    It's not that it needs sunlight to kill algae.

    FC is consumed by two things. 1. Sunlight/UV radiation and 2. Organics or cleaning other junk from the pool. If the pool is clean already, the only thing that will consume FC is sunlight. If the pool is clean and it's night time, nothing is consuming chlorine, so it just sits in the pool doing nothing until morning. At that point, the pool is still clean, but sunlight will start burning it off again.

    Because sunlight always consumes chlorine, you have to always account for the fact that a clean pool will always go through "some amount" every day.
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    Mod Squad Bama Rambler's Avatar
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    Re: OCLT during the daytime, and bleach drip feeder wasteful

    Thanks Dave and Smy. That's exactly what I meant. If the pool is sanitized the chlorine is just sitting there waiting on something to come along. If nothing else comes along it just sits until the sun comes up.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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