Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 8 of 8

Thread: Determining Gallons Size

  1. Back To Top    #1

    Join Date
    Jul 2009
    Location
    Long Island, NY
    Posts
    238

    Determining Gallons Size

    I am starting to question how many gallons our new IG pool is. It is an 18' x 38' free form with a surface area of 640.1 square foot. The shallow end is 3' and the deep end is 8'. The engineer's drawings indicated that the volume is approximately 23,000 gallons but I'm not sure that is accurate. We just added 182 oz of 6% bleach and it raised the FC from 0 to 5. Using the pool calulator, that increase corresponds to roughly an 18,000 gallon pool. We also just added 8 pounds of 100% CYA. I will test the CYA levels a week from now using the TF Test kit and see what the level is. If the CYA level turns out to be around 50, is it safe to assume that my pool is around 18,000 gallons instead of the 23,000 gallons that I though it was? I am trying to back into the pool size by knowing what effect a given amount of chemicals has on the water. Will this work?

    I looked at this a different way by calculating the volume of the 3' deep shallow end across the entire surface area of the pool (640.1SF x 3FT x 7.48 GAL/CF = 14,364 gallons). Is it reasonable to assume that the deep end adds another 3,636 gallons to bring the total up to 18,000 gallons?

    Thanks in advance for any comments or advice.
    Free-form concrete walls with vinyl liner, 18,000 gallon capacity, Jandy 1.5HP e-Pump, Jandy DEV48 DE filter (using cellulose media), Jandy AE2500 heat pump, Jandy Aqualink Power Center with 14-blade cell kit and Jandy PDA-P8 wireless control system.

  2. Back To Top    #2
    Mod Squad Bama Rambler's Avatar
    Join Date
    Jun 2009
    Location
    SouthWest Alabama
    Posts
    21,774

    Re: Determining Gallons Size

    I get 17,907 when I calculate it so I'd bet that 18000 is pretty darn close. Figuring the volume by backing out of the chem changes is not a bad way to double check the volume either. The engineer most likely included the size all the way to the top of the coping in their calcs.
    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

  3. Back To Top    #3

    Join Date
    Jul 2009
    Location
    Long Island, NY
    Posts
    238

    Re: Determining Gallons Size

    Thanks, I just wanted to see if anyone else has done it this way and how accurate of a method it is. The CYA test next week should confirm my assumption about the volume.
    Free-form concrete walls with vinyl liner, 18,000 gallon capacity, Jandy 1.5HP e-Pump, Jandy DEV48 DE filter (using cellulose media), Jandy AE2500 heat pump, Jandy Aqualink Power Center with 14-blade cell kit and Jandy PDA-P8 wireless control system.

  4. Back To Top    #4
    reebok's Avatar
    Join Date
    Apr 2009
    Location
    Lakeland, FL
    Posts
    1,268

    Re: Determining Gallons Size

    there are 3 or 4 different methods here that may be better than the cya test:
    estimating-a-free-form-pool-volume-t11772.html
    16x32 21,000 gallon in-ground exposed aggregate, 1.5hp pump, 120 sqft catridge filter, birdcage, solar panels, aquavac tigershark qc robot.

  5. Back To Top    #5

    In the Industry
    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    28,398

    Re: Determining Gallons Size

    ! would be concerned the FC would not be precise....it degrades too rapidly in the day.

    CYA test is pretty subjective and not very accurate.

    A combination of calculations would probably end up being better than either of those tests unless you did the FC test at night within 30 min of each other.
    Dave S. - Forum owner
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  6. Back To Top    #6

    Join Date
    Jun 2009
    Location
    Vero Beach, FL
    Posts
    462

    Re: Determining Gallons Size

    I think 23,000 gallons is right. If your area is 640, and your average depth is 5.5 feet [(3+8)/2], then that gives you 640 x 5.5 x 7.48 = 26,330 gallons. However, because you have a freeform shape and we don't know the actual slope of the bottom, it could vary quite a bit from this number.
    25' x 13' Roman, 12000 gal IGP, Plaster, with 500 gal Spa
    SWG, 1 HP Max Flo Pump, C-900 cartridge filter
    Solar heat

  7. Back To Top    #7

    Re: Determining Gallons Size

    Quote Originally Posted by poolneophyte
    Thanks, I just wanted to see if anyone else has done it this way and how accurate of a method it is. The CYA test next week should confirm my assumption about the volume.
    I did adjust my pool size by using the Pool Calculator backwards. After some observations following adding muriatic acid to my pool, I decided that it was about 1000 gallons more than the pool builder stated. Most likely that is the 700 gallons of the spa, plus some piping runs. I think the only way to be sure is to read the water meter as it is being filled up.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

  8. Back To Top    #8
    Guest

    Re: Determining Gallons Size

    If you want to determine the volume chemically here is a method that works well:
    http://www.poolhelp.com/ChemicallyDeriv ... olumes.pdf
    Here is the dosage chart that they talk about in the procedure above:
    http://www.poolhelp.com/SimplifiedDosageFormulas.pdf
    I've used it several times on different pools and it gets you in the ballpark and then some.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •