Mystery Pool Capacity

[revitup]

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!?

 

[YippeeSkippy]

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]

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]

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.

 

[revitup]

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]

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 Levels), but it would seem that your FC level is fine and will fall on its own. Curious.

 

[revitup]

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 Levels), 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]

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

 

[RMcGirr83]

Pretty sure there are 7.5 gallons of water in one cubic foot?

 

[revitup]

7.48052 to be exact.

 

[JamesW]

7.4805194805 to be more exact.

When measuring pool volume, I like to get down to +/- 1 cubic Planck length. Just saying.

 

[Etchase]

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]

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]

Here are my specs

 

[revitup]

Here are my specs

That is VERY similar to my pool. I'm estimating they are both closer to 9000 gallons, certainly no more than 10K. My PoolMath calculations seem to work pretty good using 8K.

 

[JW1]

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.

 

[JW1]

Here is one more pool with the same design. This manufacturer states it is 9800 gallons.

 

[YippeeSkippy]

Glad to hear you found your "happy place". Hows the pool been otherwise? I imagine you can't wait for Spring, huh?

Maddie

 

[revitup]

Maddie, you don't know! We are really looking forward to our first full pool season.
That San Lucas pool is very close to ours in design and dimensions, the stated 9800 gallons is pretty believable given my back of the hand calculations and measured chem addition results. I'm still using 8000 gallons in my Pool Math app and I always seem to be a little low. Not a bad thing but I'll probably bump that up a little at some point (8500 or 9000 probably) to see if I can fine tune it a little.
The pool has been very easy to maintain and has stayed crystal clear all winter, just a little leaf debris on the bottom and of course the yellow pollen now that that season is here. Just a solar cover and leaf net over it. Salt cell seems to like the single digit setting to maintain FC with the cool temp. I probably check chems way more often than I need to but I kind of enjoy it (I know, another crazy retiree).

 

[JW1]

Since I’ve opened my pool last Friday and doing daily testing and treatment I am experiencing the same issue of overshooting my nightly addition of LC. I’m currently using 10,000 on PoolMath. I have a walking ledge in mine, do you? Maybe I’ll put in 9000 gallons tonight and see what happens. Is 8500 gallons your best daily estimation so far?