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Thread: New pool owner - Calculating the volume & plumbing tutorial?

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    Join Date
    Aug 2007
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    New pool owner - Calculating the volume & plumbing tutorial?

    Hello. I'm new to the forum and very glad I found it.

    We just bought a house in Texas (we're from upstate New York) and have never owned or maintained a pool before.

    I'm trying to get a handle on testing, chemicals, etc, because I'm generally a DIY type person (read: cheap & anal retentive).

    In trying to estimate the volume, I've come up with 11K, 13K & 15K gal. using the various formulas.

    The best description of the pool shape would be a trapezoid with curves instead of sharp angles. I have the notes & proposal from the pool builder, but can't find the volume listed anywhere. It's 17x31 ft, 417 sq ft with an 81 ft perimeter. The pool depth is listed as "3x5x3" - there's a 5' deep section in the middle and 2 3' deep sections at the ends. Can anyone shed light on which volume I should use?

    Also trying to get a handle on the plumbing. There's 1 input to the pump, so I assume the skimmer & drain are plumbed into a manifold or "T". From the pump it goes to the cartridge filter. Out from the cartridge filter into a T with a drain/waste spigot on one side. The other side of this T goes to a Jandy 3 way valve, one side of this valve seems to go to the returns/jets (as I close off this side a little, pressure on the jets decreases) and the other goes to a Jandy energy filter, then to the polaris pool vac output/quick connect on the side of the pool, near the skimmer. Does this setup make sense?

    Thanks for any input - I'm looking forward to learning about & caring for my new toy!
    13K gal - IG gunite/plaster - 1 1/2 HP pump - 300lb. sand filter - SWCG
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    JasonLion's Avatar
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    I would go with 13,000 gallons as a starting estimate. Getting an exact number isn't critical. You can adjust your size estimate over time as you see what effect adding chemicals based on that estimate has.

    Your plumbing setup sounds reasonable, though not ideal. I suspect the main drain is probably plumbed into the skimmer. Check to see if you have two pipes at the bottom of the skimmer. The three way valve before the engery filter is designed to allow you to adjust the pressure that the cleaner gets.
    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

  3. Back To Top    #3

    Join Date
    May 2007
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    Houston, Texas, USA
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    Re: New pool owner - Calculating the volume & plumbing tutorial?

    Quote Originally Posted by TFPJules111
    Hello. I'm new to the forum and very glad I found it.

    We just bought a house in Texas (we're from upstate New York) and have never owned or maintained a pool before.

    I'm trying to get a handle on testing, chemicals, etc, because I'm generally a DIY type person (read: cheap & anal retentive).

    In trying to estimate the volume, I've come up with 11K, 13K & 15K gal. using the various formulas.

    The best description of the pool shape would be a trapezoid with curves instead of sharp angles. I have the notes & proposal from the pool builder, but can't find the volume listed anywhere. It's 17x31 ft, 417 sq ft with an 81 ft perimeter. The pool depth is listed as "3x5x3" - there's a 5' deep section in the middle and 2 3' deep sections at the ends. Can anyone shed light on which volume I should use?

    Also trying to get a handle on the plumbing. There's 1 input to the pump, so I assume the skimmer & drain are plumbed into a manifold or "T". From the pump it goes to the cartridge filter. Out from the cartridge filter into a T with a drain/waste spigot on one side. The other side of this T goes to a Jandy 3 way valve, one side of this valve seems to go to the returns/jets (as I close off this side a little, pressure on the jets decreases) and the other goes to a Jandy energy filter, then to the polaris pool vac output/quick connect on the side of the pool, near the skimmer. Does this setup make sense?

    Thanks for any input - I'm looking forward to learning about & caring for my new toy!
    Welcome to TFP!
    Freeform shaped pools are difficult to calculate the volume accurately without having dimensioned drawings of the pool, including the shape (cross section) of the bottom. Having said that, an 81 ft perimeter would be equivelant to a square pool 20.25 x 20.25, (410 sq ft) which matches pretty close to your 417 sq ft surface area. Anyway, using 417 sq ft surace area, and average depth of 4 ft, I come up with 12,476 gallons. Using 410 sq ft surface area (20.25 x 20.25), and average depth of 4 ft, I get 12,267 gallons. Fyi, (and you may already know this) many formulae use 7.5 gallons per cubic foot, when it's actually 7.48.

    Can't help on the plumbing, sorry.
    Poor Man's Pool
    Doughboy 18 ft round above ground
    7600 gal with center drain
    Pentair sand filter, 1 HP pump
    50 ppm borates
    "I know just enough to be dangerous"
    Pool Calc Ver 1.41 (Excel)

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    Join Date
    Aug 2007
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    Denton, TX
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    Thank you both for the quick replies. I see I came to the right place.

    Your plumbing setup sounds reasonable, though not ideal. I suspect the main drain is probably plumbed into the skimmer. Check to see if you have two pipes at the bottom of the skimmer.
    Yep, 2 Pipes. So the drain goes into the skimmer, then from the skimmer to the pump input? The skimmer has a puck-like piece at the bottom, with an adjustable vent/door on it. What does the vent control and how should it typically be set for normal operation?

    The three way valve before the engery filter is designed to allow you to adjust the pressure that the cleaner gets.
    I'd found that out by playing with it. If the pressure gauge on the energy filter doesn't read 0 with the pump off (switched off, not shut off at the valve), it needs to be replaced, right?
    13K gal - IG gunite/plaster - 1 1/2 HP pump - 300lb. sand filter - SWCG
    Support TFP!

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    JasonLion's Avatar
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    May 2007
    Location
    Silver Spring, MD
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    37,879
    The vent thing in the bottom of the skimmer should control how much water is drawn from the skimmer and how much comes from the main drain. Normally you want about half and half.

    Many pool pressure meters tend to fail after a year or two. A non-zero reading with the pump off is a fairly clear sign of problems.
    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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