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Thread: Pool size question

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    Pool size question

    I was checking my pool, I tested and my FC was 0.5 so the pool calculator told me for 16000 Gal. (what I thought I had) I needed to add 123 oz of chlorine to get m to 8 FC (CYA of 50). So I did that and 3-4 hours later I checked and it was at 7... I messed with the numbers and it looks like my pool may be 18500 gal... because if I had it set at 18500 and set it so i was at 0.5 FC and wanted to get to 7 it shows add 123 oz (if you are following me)...

    I am looking for a way to back up my findings... I have a pool that I think is 16x33 rectangle with rounded corners, and steps at both ends... its a Foxx Sport pool that is about 3.5 on both sides to 5.5 in the middle (need to get my tape out to be 100% sure on measurements). I cant find a calculator to show me average depth with two shallow ends... does that sound like 18500 to you?

    thanks for any thoughts...

    only pic on hand:
    Pool 16 x 33.5 Foxx Pool with rounded corners 3.5 at each end and 5+ in the middle (16000 GAL)

    Equipment - 300 LB Hayward filter with a Pentair SuperFlo pump (3/4 HP). Also Hayward H series Heater and a dedicated jet for a Polaris 280 with a booster pump (3/4HP). Hayward Chlorinator CL200.

    Pool has Main Drain, 2 return Jets with 1 inch eyeballs, a skimmer with floating weir, and the dedicated Polaris jet. Also has a valve for the Waterslide.

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    Saturn94's Avatar
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    Re: Pool size question

    If it was sunny it's possible you dosed correctly and 1ppm was lost over the 3-4 hour period before you tested.
    20k IG vinyl liner/Aqua Rite SWCG, T-15 cell/Hayward Pro Grid 6020 DE filter/Polaris 280 with booster pump/Hayward Superpump 1 hp/city water/pool installed March 2004

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    Re: Pool size question

    It was after the sun was setting... I'm going to set it at 18500 and do some testing tomorrow... Will see what it does???
    Pool 16 x 33.5 Foxx Pool with rounded corners 3.5 at each end and 5+ in the middle (16000 GAL)

    Equipment - 300 LB Hayward filter with a Pentair SuperFlo pump (3/4 HP). Also Hayward H series Heater and a dedicated jet for a Polaris 280 with a booster pump (3/4HP). Hayward Chlorinator CL200.

    Pool has Main Drain, 2 return Jets with 1 inch eyeballs, a skimmer with floating weir, and the dedicated Polaris jet. Also has a valve for the Waterslide.

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    Scuba_Steve's Avatar
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    Re: Pool size question

    My math says 19077.12g. This is assuming that the pool slopes from 3.5 to 5.5 for 1/3 of the pool, stays 5.5 for 1/3, and slopes back again. That is also with sharp corners, not rounded, so a little less.

    - - - Updated - - -

    If it goes from 3.5 to 5.5 then with no hold at 5.5 goes back to 3.5 then my math shows 17773.71g
    6425g Intex Ultraframe 18'x48" AG
    Stock 1500gph cartridge filter / Intex SWG CG-28669 with E.C.O.
    Install date: 5/26/2015
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    Re: Pool size question

    Let me know if you want to know how I got those numbers...
    6425g Intex Ultraframe 18'x48" AG
    Stock 1500gph cartridge filter / Intex SWG CG-28669 with E.C.O.
    Install date: 5/26/2015
    TF-100
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    BoDarville's Avatar
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    Re: Pool size question

    I was checking my pool, I tested and my FC was 0.5 so the pool calculator told me for 16000 Gal. (what I thought I had) I needed to add 123 oz of chlorine to get m to 8 FC (CYA of 50). So I did that and 3-4 hours later I checked and it was at 7... I messed with the numbers and it looks like my pool may be 18500 gal... because if I had it set at 18500 and set it so i was at 0.5 FC and wanted to get to 7 it shows add 123 oz (if you are following me)...
    I do follow you and that is a good way to get a handle on the volume of your pool. I would go with the 18,500 gallon as the volume for your next dose and see if the actual target value matches your starting point + the amount you dosed. Fine-tuning the volume amount is best done with the chlorine additions since that is done on a daily basis during the swim season. I would also test the volume measurement when you add other chemicals.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
    A good test kit is an investment, not an expense.

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    Re: Pool size question

    Thanks guys... It is more of a 1/3 3.5 - 1/3 5.5 - 1/3 3.5 kind of like this:

    \_/ - but not as severe of a slope.

    I will check my doses tomorrow and see... Sounds like with Steves math and rounded corners I may be close... More updates after tomorrow.
    Pool 16 x 33.5 Foxx Pool with rounded corners 3.5 at each end and 5+ in the middle (16000 GAL)

    Equipment - 300 LB Hayward filter with a Pentair SuperFlo pump (3/4 HP). Also Hayward H series Heater and a dedicated jet for a Polaris 280 with a booster pump (3/4HP). Hayward Chlorinator CL200.

    Pool has Main Drain, 2 return Jets with 1 inch eyeballs, a skimmer with floating weir, and the dedicated Polaris jet. Also has a valve for the Waterslide.

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    Scuba_Steve's Avatar
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    Re: Pool size question

    Quote Originally Posted by myrddin View Post
    Thanks guys... It is more of a 1/3 3.5 - 1/3 5.5 - 1/3 3.5 kind of like this:

    \_/ - but not as severe of a slope.

    I will check my doses tomorrow and see... Sounds like with Steves math and rounded corners I may be close... More updates after tomorrow.
    That is exactly how I calculated my first set of numbers. I would say your pretty dead on with your 18500g estimate. In fact I was going to use the \_/ but figured the steep angles might get lost in translation. I guess ""--__--"" would be more appropriate.
    6425g Intex Ultraframe 18'x48" AG
    Stock 1500gph cartridge filter / Intex SWG CG-28669 with E.C.O.
    Install date: 5/26/2015
    TF-100
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    ship of fools's Avatar
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    Re: Pool size question

    I am 16 x 32 with an. 8 ft deep end and i am around 21,000 gallons so you are definitely in the ballpark


    21,000 gallon inground
    Haywood Sand Filter
    Vinyl Liner

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    Re: Pool size question

    I think you're overly stressing getting the exact volume of the pool. Your FC test is +-1 drop each time, or +-.5 ppm each test. The delta between two test could be 1 full ppm off, even if you do everything perfectly. Then you have to remember that bleach/chlorine strength can easily be off by 10 or 20 percent based on freshness. These aren't lab standard chemicals.

    To me, this information puts pool volume in the "good enough" category. Horseshoes and hand grenades, as the old saying goes. Estimate something in the rough ballpark, and refine only if you see any significant discrepancies. A couple thousand gallons either way is pretty insignificant.
    15k in-ground plaster, Hayward C900 cartridge, 3/4hp single speed pump, Barracuda G2 cleaner, TF-100

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    Re: Pool size question

    OK I finally have some time to fool with this... my water tested at 4 for FC... I added 57 OZ of 12.5 (Pool Shock) or Sodium Hypochlorite... I have the calc currently set at 18600 GAL... one hour later I checked it and I only see it has raised up .5 (4.5 total). What I am doing is trying to make sure I not only have the right GAL for the pool but make sure I reach no less than FC 4 by the time I need to add in the evening. MY CYA is at 50... no loss over night.

    did I not wait long enough? my pump is VS and set low... I may go out and run the clean cycle so it moves the water faster.

    let me know what you folks think...
    Pool 16 x 33.5 Foxx Pool with rounded corners 3.5 at each end and 5+ in the middle (16000 GAL)

    Equipment - 300 LB Hayward filter with a Pentair SuperFlo pump (3/4 HP). Also Hayward H series Heater and a dedicated jet for a Polaris 280 with a booster pump (3/4HP). Hayward Chlorinator CL200.

    Pool has Main Drain, 2 return Jets with 1 inch eyeballs, a skimmer with floating weir, and the dedicated Polaris jet. Also has a valve for the Waterslide.

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    Re: Pool size question

    I would think the best path is to call Foxx Pools and ask them the gallonage.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Pool size question

    well I did call, and she said that a pool that is 33 feet long by 16 feet wide with a 5.5 foot center and each end at 3.5 would be 9100 GAL... I asked her to check that twice.

    needless to say I am still trying to figure it out.
    Pool 16 x 33.5 Foxx Pool with rounded corners 3.5 at each end and 5+ in the middle (16000 GAL)

    Equipment - 300 LB Hayward filter with a Pentair SuperFlo pump (3/4 HP). Also Hayward H series Heater and a dedicated jet for a Polaris 280 with a booster pump (3/4HP). Hayward Chlorinator CL200.

    Pool has Main Drain, 2 return Jets with 1 inch eyeballs, a skimmer with floating weir, and the dedicated Polaris jet. Also has a valve for the Waterslide.

  14. Back To Top    #14

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    Re: Pool size question

    ok I re measured: 34 foot 2 inches to where the wall meets the steps (rounded corners) and 16 feet wide. the middle is approx 5 foot deep (Might be 5.5 or close at the maindrain) and its 3 foot deep at the steps and that slopes to the 5 foot section.
    Pool 16 x 33.5 Foxx Pool with rounded corners 3.5 at each end and 5+ in the middle (16000 GAL)

    Equipment - 300 LB Hayward filter with a Pentair SuperFlo pump (3/4 HP). Also Hayward H series Heater and a dedicated jet for a Polaris 280 with a booster pump (3/4HP). Hayward Chlorinator CL200.

    Pool has Main Drain, 2 return Jets with 1 inch eyeballs, a skimmer with floating weir, and the dedicated Polaris jet. Also has a valve for the Waterslide.

  15. Back To Top    #15
    Scuba_Steve's Avatar
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    Re: Pool size question

    17634.07 using 3ft/5ft/3ft, sharp corners.
    18990.54 using 3ft/5.5ft/3ft, sharp corners.

    I rounded off the extra 2 in in length btw.
    6425g Intex Ultraframe 18'x48" AG
    Stock 1500gph cartridge filter / Intex SWG CG-28669 with E.C.O.
    Install date: 5/26/2015
    TF-100
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  16. Back To Top    #16
    Scuba_Steve's Avatar
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    Re: Pool size question

    BTW, you lose approximately 310 gallons due to the rounded corners at 3' deep and gain about 450g with the cutouts for your stairs.

    This is purely by eyeballing measurements.

    Sorry, I love doing random practical math equations! Call me a nerd... :P
    6425g Intex Ultraframe 18'x48" AG
    Stock 1500gph cartridge filter / Intex SWG CG-28669 with E.C.O.
    Install date: 5/26/2015
    TF-100
    Helpful Links

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    Re: Pool size question

    man... can you share how you did that, I have been racking my brain trying to figure it out.

    - - - Updated - - -

    should I go with 18,900 due to the cut outs?
    Pool 16 x 33.5 Foxx Pool with rounded corners 3.5 at each end and 5+ in the middle (16000 GAL)

    Equipment - 300 LB Hayward filter with a Pentair SuperFlo pump (3/4 HP). Also Hayward H series Heater and a dedicated jet for a Polaris 280 with a booster pump (3/4HP). Hayward Chlorinator CL200.

    Pool has Main Drain, 2 return Jets with 1 inch eyeballs, a skimmer with floating weir, and the dedicated Polaris jet. Also has a valve for the Waterslide.

  18. Back To Top    #18
    Scuba_Steve's Avatar
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    Re: Pool size question

    The formula for gallonage is Length*Width*Depth/231. This is in inches.

    So for your pool first figure out depth. First slope = (3+5)/2 = 4. Middle = 5. Second slope is same as first = 4. Average them = (4+5+4)/3 = 4.33

    Now plug them in and convert to inches. 34*12*16*12*4.33*12/231 = 17620.51. I left on the endless string of 4.333333 which my initial calc was a little higher.

    For corners:
    Figure out area of surface of square corners. I guesses 48" for each side and 36" for depth. 48*48*36/231*4 corners = 1436.26
    Figure out area of curved corners. Area of a circle is pi*r*r. All 4 corners added together will make a circle. So 3.14*48*48*36/231 = 1127.46
    Subtract the two numbers to figure out the amount of gallons lost. 308.8. I rounded to 310

    Im not going to go into stairs. Im tired of typing right now lol.
    6425g Intex Ultraframe 18'x48" AG
    Stock 1500gph cartridge filter / Intex SWG CG-28669 with E.C.O.
    Install date: 5/26/2015
    TF-100
    Helpful Links

  19. Back To Top    #19

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    Re: Pool size question

    ha, you lost me somewhere around the beginning.. but that's OK... I will boost it up to 18900 and see what it looks like... in the past I had been adding chlorine 2 times a day, but based on 16000 gal... so it was a hidden error... now I am trying to add Chlorine once a day (at dusk) well its too low as you would guess... I may even need to shock because I cant seem to make sense of the numbers... I add chlorine and I don't see much of a change... might be something starting up... So I will check it agn in an hour... if its not 7 or dang close, I will take it up to 20 and keep it there for a while and try over night test agn... (honestly) it passed the test the day before yesterday so I don't see what the deal is.
    Pool 16 x 33.5 Foxx Pool with rounded corners 3.5 at each end and 5+ in the middle (16000 GAL)

    Equipment - 300 LB Hayward filter with a Pentair SuperFlo pump (3/4 HP). Also Hayward H series Heater and a dedicated jet for a Polaris 280 with a booster pump (3/4HP). Hayward Chlorinator CL200.

    Pool has Main Drain, 2 return Jets with 1 inch eyeballs, a skimmer with floating weir, and the dedicated Polaris jet. Also has a valve for the Waterslide.

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