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Thread: DOS for water changes

  1. #1
    Reef Tank Addict
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    DOS for water changes

    I’ve been doing water changes for a few months now, and it occurred to me that because the recommended programming has water going in and out simultaneously, I’m losing new water with these changes. Shouldn’t the old water come out first, and the new water follows? If so, the pumps would have to shut down while the water is being removed, correct? If I’m right, can anyone recommend a program for me?

    Jeff

  2. #2
    Frequent Contributor zombie's Avatar
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    It's not worth doing that IME. The amount of new water "lost" in miniscule compared to removing first then adding. A 30% continuous water change exactly matches a 26% batch change but the ease of use and the extra stability on parameters is worth the small amount of extra water changed.

    You might be an engineer if...You have no life and can prove it mathematically.

  3. #3
    Frequent Visitor
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    But for us OCD people, I prefer OSW out then NSW in!
    This will only work if you don't use the standard method of ATO, as in floats, optics, etc...
    because removing the water with this method will mess up your ATO.

    I use/used a Litermeter III for my ATO (now a second DOS), so it's not float controlled.
    My sump will allow 3 gallons to be removed before it gets to the point that the return pump
    starts to suck air. This will allow me to do (2) 4800 ml (1.26 gal)per day water change cycles.
    12:00am - 5:00am OSW out
    6:00am - 11:00am NSW in
    12:00pm - 5:00 pm OSW out
    6:00pm - 11:00pm NSW in
    As a backup, I have a High Level and Low Level float in the return chamber of the sump. Either one will
    shut the DOS off. High will shut the NSW side off, Low the OSW side off. There is a lot more to this, and
    I can explain more if you decide to go this route.

    NSW
    NSW1.JPG

    NSW3.JPG

    NSW2.JPG

    OSW
    OSW1.JPG

    OSW2.JPG

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