Mystery Pool Capacity

revitup

Active member
Nov 30, 2019
25
Pawleys Island, SC
I just can't believe that I can't get an rational answer to a basic question regarding the capacity of this pool. Got a call back from the manufacturer, Carribean Bay. They say it's 14000 gallons to halfway up the skimmer. "We've been using that number for 15 years" they say.
There is no way this pool is 14K gallons. I can do basic math! Even if it was a rectangle, 28.5' x 13' x 4.2'(avg depth, 64"deep end, 36"shallow end) that would be 11640 gallons. It's not a rectangle. It's a freeform shape with seats and steps. My calculation put the surface area, not counting seats and steps, at about 248 sq ft. 248 x 4.2 = 1042 cu ft. 1042 x 7.48 = 7794 gallons. Even rounding up for seats and steps, 8000 gallons.
Using the PoolMath app to calculate chems, the capacity that works in the calculations seems to be in the 7000 - 8000 range.
What the heck is going on!?
CALYPSO.jpg
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
11,668
Evans, Georgia
I still think its around 10,000-11,000...taking into consideration that large tanning area I deduct ~700 gallons.

Our pools are almost the same except mine is a rectangle.
 

revitup

Active member
Nov 30, 2019
25
Pawleys Island, SC
A fairly experienced pool guy told me that the capacity of freeform pools such as mine can be 'guesstimated' by taking the length x width as if it's a rectangle and then reducing that area by 20%. Using that method I get 9300 gallons. Still not even close to 14000. A bit closer to my 8000 calculation.
That 'large tanning area' is just a large step, about big enough to seat 3 people.
 

JJ_Tex

Bronze Supporter
Jul 17, 2019
447
Prosper, TX (DFW)
I was able to call my water company and they could tell me the exact hours I was filling, and calculate the amount of usage I had during that time. It seems accurate, and took the nice lady on the phone about 30 seconds to figure it out.
 
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revitup

Active member
Nov 30, 2019
25
Pawleys Island, SC
I was able to call my water company and they could tell me the exact hours I was filling, and calculate the amount of usage I had during that time. It seems accurate, and took the nice lady on the phone about 30 seconds to figure it out.
My pool was filled from a fire hydrant and I don't believe the water company would be tracking that. There was a meter attached to the hydrant attachment and, had I known this was going to be so difficult, I could have noted the beginning and end readings. Who'd have guessed.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I found THIS website that shows it as 12K gallons. I would use that as a starting point. Then when you do chemical adjustments via the PoolMath tool or APP, you can see if your dosage resulted in going over or under your goal, then modify your 12K estimate from there.

On a side note I have to ask .... why are you using sodium thiosulfate? I believe your FC was only about 7.5 or so, and you were trying to lower it to about 5.5? You didn't post your CYA which directly impacts the proper FC level (see FC/CYA Chart), but it would seem that your FC level is fine and will fall on its own. Curious.
 

revitup

Active member
Nov 30, 2019
25
Pawleys Island, SC
I found THIS website that shows it as 12K gallons. I would use that as a starting point. Then when you do chemical adjustments via the PoolMath tool or APP, you can see if your dosage resulted in going over or under your goal, then modify your 12K estimate from there.

On a side note I have to ask .... why are you using sodium thiosulfate? I believe your FC was only about 7.5 or so, and you were trying to lower it to about 5.5? You didn't post your CYA which directly impacts the proper FC level (see FC/CYA Chart), but it would seem that your FC level is fine and will fall on its own. Curious.
That pool is a different manufacturer and model and significantly bigger than mine.
I have used a couple of different apps including PoolMath and, as I mentioned previously, the results indicate that the true capacity is between 7K - 8K.
I was using sodium thiosulfate at to lower my FC level. As a new pool owner I was trying to follow the 'conventional' recommendation for FC level of 1.0 - 3.0 for a salt pool. Was still experimenting with salt cell output, hadn't yet made the connection between CYA and FC level, and hadn't discovered TFP yet . I know better now and also now have my salt cell output under somewhat better control.
 

kimkats

Mod Squad
LifeTime Supporter
Jul 10, 2012
41,557
Tallahassee, FL
Good job on learning and using the best way to care for your pool.

Moving forward you should use the gallons your chemicals say you have as that is what the testing of the water is saying. You can dial in the size as you move forward with learning your pool and it's need.

Kim:kim:
 

Etchase

Active member
May 22, 2019
31
Hawaii
You could utilize the acid demand test included with your Taylor kit, and then add acid until you achieve the desired PH in the pool. You can back calculate the capacity to within 20% or so, which is good enough. A large pH change is what’s required for this to be useful, and is probably the best chance of getting an estimate within a couple of hours. Acid has an accurate stated strength, and pH usually stabilizes in 15 minutes or so after adding. Just be aware that pH can rise pretty quickly when it’s originally close to the low 7’s.
 

JW1

Member
Sep 4, 2019
23
Ohio
I have a very similar fiberglass poll design. Mine is the Grand Cayman from Sun Pool. Manufacturer states it is 14,000 gallon pool. I agree with you that it doesn’t seem quite accurate.
 

JW1

Member
Sep 4, 2019
23
Ohio
I wasn’t home the day when the PB had the water truck fill up the pool. The cost for water was $360. So I can assume $90 a load which most likely be between 2,000. -2,200 Gallons per load and a total of four loads. I did fill some water the first night the pool was installed with the garden hose to just give it a bit of weight per the PB. So based on that a total of 9000 gallons is probably a good estimate. I do have a walking ledge. Regardless I think your gallon estimates are most likely correct.