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Thread: regularly changing some of the water

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    Join Date
    Dec 2013
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    SF, CA, USA
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    regularly changing some of the water

    has anyone tried or heard of doing a gradual drain & refill cycle, instead of periodically changing the water? since i am committed to autofill, autodrain is a natural possibility.

    around here, it costs $4 to fill a 500g hot tub and i might change the water every month. this is the same rate of fill as implied in dumping and refilling about 18g every night. not sure what this does to the average "age" of the water. perhaps it would not protect someone whose hot tub contains legionnaire's disease (?) and doesn't know (??), but could it work in practice?
    plumbing up wall-mounted equipment and plenty gauges below a 500G wooden outdoor hot tub.

  2. Back To Top    #2

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    Nov 2014
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    Lake Ariel, PA
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    Re: regularly changing some of the water

    I'm pretty new at this but I would think that could be a hassle. For example, if you use borates and set them to 50ppm, the gradual drain will have that level in constant flux. Same with anything else you have used to balance and lock in the test readings.
    -------------------------
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    Mod Squad pooldv's Avatar
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    Re: regularly changing some of the water

    This is how I have maintained my tub for 18 months and it recommends changing the water every 3-5 months. I may or may not adhere to that schedule.

    How do I use Chlorine in my Spa (or pool)?
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    Re: regularly changing some of the water

    For spas it's more of a hassle to have an auto-drain to go along with the auto-fill because you have to replenish the calcium for CH to prevent foaming and the borates for pH stability and you'd need to use Dichlor more frequently (instead of bleach) to maintain CYA.

    Also, you should not have to replace your water once a month. With the Dichlor-then-bleach method described in the link in the previous post, you should be able to go with the Water Replacement Interval (WRI) of at least:

    WRI (days) = (2/9) x (Spa Size in Gallons) / (# or Person-Hours Per Day)

    So in a 350 gallon spa used by one person for one hour every day or two people for 30 minutes every day that would be 77 days or around 2-1/2 months. You could even go longer. The reason is that by switching from Dichlor to bleach (except once a month using Dichlor for a day to restore CYA) one avoids CYA buildup which is the main limiting factor to how long you can go without changing the water.
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  5. Back To Top    #5

    Join Date
    Dec 2013
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    SF, CA, USA
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    Re: regularly changing some of the water

    thanks for the input about the chemical levels, folks! sounds reasonable.
    plumbing up wall-mounted equipment and plenty gauges below a 500G wooden outdoor hot tub.

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