Pool size question

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M

myrddin

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LifeTime Supporter
Aug 11, 2012
229
Southern Indiana
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:
 
If it was sunny it's possible you dosed correctly and 1ppm was lost over the 3-4 hour period before you tested.
 
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
 
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)...
Click to expand...
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.
 
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.
 
myrddin said:
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.
Click to expand...

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. :)
 
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.
 

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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...
 
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.
 
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
 
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.
 
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.
 
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