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Thread: Help with sizing Autopilot Digital SWG

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    Help with sizing Autopilot Digital SWG

    I have a 18000 gallon pool and thinking about getting a Autopilot Digital.

    I live in Texas, and haven't hit the hot summers yet, but currently losing about 2-3ppm chlorine a day (undoubtedly will go up with our very hot summers). I was trying to decide between the 35K rated SWG or the 42K rated SWG... I know bigger would mean longer cell life, but is there a disadvantage with going with the 42K SWG other than cost?

    Thanks!
    15k gunite pool. Intelliflo VF. Autopilot SWG.
    2k separate spa with waterfall (ie: pain in the rear maintaining a separate body of water). 2HP Hayward Tristar pump.

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    Mod Squad Bama Rambler's Avatar
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    Re: Help with sizing Autopilot Digital SWG

    Until you get about 3x the size of the pool with the cell size you won't have a problem. The problem with getting a cell more than 3 times the pool size is that you have to run them at such a low percentage that it's not practical.
    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
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Help with sizing Autopilot Digital SWG

    Just like Dave said the 42k will work very well with your pool.

    Any other questions for us?
    Josh Ulfers - josh@saltpoolguys.com - 888-725-8766
    SaltPoolGuys.com - AutoPilot Pool Pilot Systems, Parts & Cells - AquaCal Heat Pumps

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    Re: Help with sizing Autopilot Digital SWG

    2-3 ppm of chlorine loss is a little excessive. What Cyanuric acid level are you maintaining?
    While you're at it, what's the rest of your water chemistry test results?

    pH
    Total Alkalinity
    Calcium Hardness
    CYA
    Free Chlorine
    Total Chlorine
    Sean Assam - Sean@teamhorner.com
    National Accounts and Commercial Products Manager
    AquaCal Heat Pumps www.aquacal.com
    AutoPilot Salt Chlorine Generators www.autopilot.com

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    Re: Help with sizing Autopilot Digital SWG

    Quote Originally Posted by Poolsean
    2-3 ppm of chlorine loss is a little excessive. What Cyanuric acid level are you maintaining?
    While you're at it, what's the rest of your water chemistry test results?

    pH
    Total Alkalinity
    Calcium Hardness
    CYA
    Free Chlorine
    Total Chlorine

    4,500 gallon spa, maybe this is a party pad??
    20X40 30,000 gallon gunite pool

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    Re: Help with sizing Autopilot Digital SWG

    I don't mean to thread jack but I have been searching and not wanting to start a thread that has been covered. I just had a new liner installed in our 24k IG which is 18'x36' that has a Quad 60 DE filter. I was looking to find out what size SWG cell to get. Would the AquaRite 40k be to big? The pool store here wants to sell me a 25k.

    I'm looking at installing a Goldline AquaRite SWG system. From what I have read they are well worth it and I found the Control panel and 40K cell for $1,050 so far.
    24k IG Vinyl D.E. Filter, SWG

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    Mod Squad Bama Rambler's Avatar
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    Re: Help with sizing Autopilot Digital SWG

    PoolDad2, I'll answer your question here but it would be fine to start a new thread.

    If your pool is 24,000 gallons then a cell rated for 25,000 gallons is too small. I wouldn't even consider the 25k unit. I'd go for the 40k or even bigger.
    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
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Help with sizing Autopilot Digital SWG

    Thanks for the reply. It pretty much answered my question. I spent some serious time going over all the threads and have found many answers that I had questions on.

    This site is great!
    24k IG Vinyl D.E. Filter, SWG

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    Re: Help with sizing Autopilot Digital SWG

    Quote Originally Posted by Poolsean
    2-3 ppm of chlorine loss is a little excessive. What Cyanuric acid level are you maintaining?
    While you're at it, what's the rest of your water chemistry test results?

    pH
    Total Alkalinity
    Calcium Hardness
    CYA
    Free Chlorine
    Total Chlorine
    Well, the CYA I'm "maintaining" is more like a CYA I am slowly trying to lower:

    CYA 140
    Free chlorine 15
    Total chlorine 15
    TA 90
    pH 7.6
    CH 290

    The pool often gets lots of sun and it is starting to get a bit hot here in Texas...
    15k gunite pool. Intelliflo VF. Autopilot SWG.
    2k separate spa with waterfall (ie: pain in the rear maintaining a separate body of water). 2HP Hayward Tristar pump.

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    JasonLion's Avatar
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    Re: Help with sizing Autopilot Digital SWG

    With CYA that high and a loss of 2-3 ppm of FC per day you almost certainly have a low level algae problem. At high CYA levels it is very easy for there to be enough algae to use up lots of chlorine but not enough to be visible. It is very difficult to completely kill algae when CYA is that high.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Help with sizing Autopilot Digital SWG

    Quote Originally Posted by JasonLion
    With CYA that high and a loss of 2-3 ppm of FC per day you almost certainly have a low level algae problem. At high CYA levels it is very easy for there to be enough algae to use up lots of chlorine but not enough to be visible. It is very difficult to completely kill algae when CYA is that high.
    Can you still have an algae problem if your CC is 0? Guess I'll have to do an overnight FC loss test to make sure. Thanks for making me aware of this! I just thought it was normal.... What kind of FC loss per day would you expect if there was no algae?
    15k gunite pool. Intelliflo VF. Autopilot SWG.
    2k separate spa with waterfall (ie: pain in the rear maintaining a separate body of water). 2HP Hayward Tristar pump.

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    JasonLion's Avatar
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    Re: Help with sizing Autopilot Digital SWG

    Sure, CC can easily be zero even when you have active and visible algae.

    If there wasn't any algae, and with CYA at 140, I would expect daily chlorine usage to be below 0.5 ppm per day, possibly well below depending on how much direct sunlight you get on the pool.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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