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Math Help - Help me determine approx gallons & sqft of my pool?

  1. #1
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    Help me determine approx gallons & sqft of my pool?

    By FAR not a math wiz, many many many years out of school and no memory anymore. So the house I bought has a pool. I took some basic measurements and figured you smart guys could make my life easy and help me get approximate square footage and gallons that it could fit. The pool slopes in the deep end from 6'0" to 3'6" in the shallow, mostly gradual slope. Of course its an open container, no ceiling so not counted in measuring. It isnt exact, I'm just trying to know roughly how many gallons it holds if filled roughly to the top (it never is that high) and approximately how many sqft of pool surface there is if I chose to paint it, seal it, etc.

    This little Microsoft Paint diagram is extremely rough and totally not to scale. I got it off of a schematic that was drawn up when it was built in 1997. I can go out and measure some spots that don't have the info on the sheet, but it's cold and so if I need to, I'll do it tomorrow. Let me know what you need.

    Thanks math wiz's

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  2. #2
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    It will not give a very accurate result, but when calculating pool volumes, the typical approximation is to just take the average of the deep end and the shallow end and use that as the depth throughout. Usually the result is used for deciding how much chlorine or algaecide to put in, and a very rough estimate is good enough.

    So, the depth is (6+3.5)/2 = 4.75 feet.

    The area is (10.5*8) + (7*1) + (12*6) +(15*16) = 403 square feet.

    So the volume is (403 square feet)*(4.75 feet) = 1914.25 cubic feet, and the conversion rate is 7.48 gallons per cubic foot, so the calculation comes out to 14318.59 gallons. So you can probably use 15,000 gallons for the volume.

    If you need a more accurate result, measure the depth at the start and end of each of the four rectangles and multiply the average for each rectangle by the area of the rectangle. If the bottom slopes evenly from one side of the rectangle to the other, that should give a really accurate result.
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  3. #3
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    Fill your pool completely.
    Jump in with a gallon container.
    Empty pool

    Save time: use a 4gallon container.
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  4. #4
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    And don't lose count.

    True story: One time the water in my pool was about a half inch too high, and I decided I could bring it down using a 5-gallon bucket. I had to pull that 5-gallon bucket out about 50 times, and my back and arms were really hurting after that.
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  5. #5
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    Quote Originally Posted by hollywood View Post
    And don't lose count.

    True story: One time the water in my pool was about a half inch too high, and I decided I could bring it down using a 5-gallon bucket. I had to pull that 5-gallon bucket out about 50 times, and my back and arms were really hurting after that.
    If the water was too high, shouldn't it have emptied itself?
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    hollywood, great, yeah that makes sense, i see how you made little squares out of it and calculated them.

    the 400sqft is floor surface space, it seems. I also want to know total surface space in sqft. If I am painting (epoxy sealing paint) the pool, then i paint the walls too. So can you help me with that? Thanks, great work.

    Quote Originally Posted by hollywood View Post
    It will not give a very accurate result, but when calculating pool volumes, the typical approximation is to just take the average of the deep end and the shallow end and use that as the depth throughout. Usually the result is used for deciding how much chlorine or algaecide to put in, and a very rough estimate is good enough.

    So, the depth is (6+3.5)/2 = 4.75 feet.

    The area is (10.5*8) + (7*1) + (12*6) +(15*16) = 403 square feet.

    So the volume is (403 square feet)*(4.75 feet) = 1914.25 cubic feet, and the conversion rate is 7.48 gallons per cubic foot, so the calculation comes out to 14318.59 gallons. So you can probably use 15,000 gallons for the volume.

    If you need a more accurate result, measure the depth at the start and end of each of the four rectangles and multiply the average for each rectangle by the area of the rectangle. If the bottom slopes evenly from one side of the rectangle to the other, that should give a really accurate result.
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  7. #7
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    Quote Originally Posted by poolhelp View Post
    hollywood, great, yeah that makes sense, i see how you made little squares out of it and calculated them.

    the 400sqft is floor surface space, it seems. I also want to know total surface space in sqft. If I am painting (epoxy sealing paint) the pool, then i paint the walls too. So can you help me with that? Thanks, great work.
    The floor surface will actually be a little larger because it slants from the shallow end to the deep end, but that's not going to be a big difference.

    You can also estimate the area of the walls by using the average height. This time you multiply by the perimeter:

    (4.75)*(15+16+3+6+5+9+10.5+8+3.5+23)=470.25 square feet

    That, plus the 400 square feet for the bottom makes 870 square feet.



    Quote Originally Posted by Prove It View Post
    If the water was too high, shouldn't it have emptied itself?
    The water needs to be at a certain level for the skimmer to work properly, which is about 4 inches below the rim. I didn't want to backflush for various reasons, and I couldn't wait for it to evaporate, so I was kind of stuck. Now I have a valve that allows me to dump water without backflushing.
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