# Thread: Pool build in Alabama - Help with calculating gallons.

1. ## Calculating pool volume question

Ok, so I know how important it is to know how many gallons my pool holds. I understand how to use my width, length and average depth to calculate? But how do I factor in the Grecian corners? Maybe I am getting way ahead of myself, pool not even started yet, but at age 52, I have to ask things while still fresh in my mind and I do tend to be a little OCD at times. Plans for pool: 18x36 IG vinyl grecian shape, sport pool. 3.5 on each and 5' 6" in the center. PB drew it out for us and shows a 2 feet width in the middle for the deepest part. Is it better to over or under estimate gallons? Is there another way to get this number? This may be a stupid question, but is there any way to get an exact volume as we fill it?

2. ## Re: Calculating pool volume question

You can get a water meter that will go on your fill hose to find out exactly how much water you put into the pool.

Using a calculation for an oval pool will give you a fairly close number, especially if the deep part in the middle has sloped walls.

3. ## Pool build in Alabama - Help with calculating gallons.

Ok so PB broke ground 6-28-12. Water going in today. Pictures to follow. Help with calculating the gallons. I plugged into the calculator to estimate size. Using 18 feet x 36 feet and 4.2 for average depth (both shallow ends are 3.5 and middle deep part is 5.5 feet)( I calculated as 3.5 + 3.5 + 5.6 divived by 3). If I use the rectangle shape it gives me 20400 and if I use the oval it gives me 18200. We have steps full width on one end and a bench full width on the other. My guess would be to go with the smaller amount. Is it better to under or over estimate?

4. ## Re: Pool build in Alabama - Help with calculating gallons.

More pictures of progress.

5. ## Re: Pool build in Alabama - Help with calculating gallons.

And today, liner in and started filling.

6. ## Re: Pool build in Alabama - Help with calculating gallons.

Great looking pool and the workmanship, particularly on that vermiculite floor, looks first class. Tell us more about the pool. Did the PB custom order that liner or does he build to that standard size?

Have you tested your fill water? Well or municipal?

I think I would estimate the square portion of the pool first. Then, I would add only one end to the total as if the bench was moved to sit on top of the steps almost eliminating the step end but now making the other end easier to calculate now that the bench is "gone".

7. ## Re: Pool build in Alabama - Help with calculating gallons.

Looking nice!

I used the following link to calculate my future project and there are many more. Googled 'pool volume'. They might not be as exact as you are wanting tho.

http://www.poolandspachemicals.co.uk/volcalc.htm

8. ## Re: Pool build in Alabama - Help with calculating gallons.

We had multiple options to choose from. We could have chosen the white steps added to one end vs what we decided on. Then the width of the stairs. We chose to have the top stair be wider, a good place for little GD to play. We have 2 PVC pipe sleeves at each end for umbrellas. The bench with jets was also an option we were able to customize. In our last pool, there was no real place to just sit and relax, except for the stairs. We were also able to choose all the depths. The liner was then constructed specifically for our pool. The pool is now full of water. The PB still needs to come back to add the salt and get all the equipment running. Based on the number of salt bags he has on hand and the chart on the side of the bag, he is adding enough salt for an 18500 gal pool. I will use the suggestions to calculate my volume. Thanks. My husband is still a little skepticle about my plans to maintain this pool WITHOUT the pool store. But I think I will be able to convince him, especially if I can show him how much money I can save him. Right now he is consumed by all the landscaping stuff, grading, laying sod, planning a retaining wall, all DYI projects. I'll post new pictures when all that stuff gets done.

9. ## Re: Pool build in Alabama - Help with calculating gallons.

Have you tested your fill water? Well or municipal?

Municipal

FC 1.5
CC 1
pH 7.5
TA 30
CH 50
CYA 0

11. ## Re: Pool build in Alabama - Help with calculating gallons.

Excellent water. I would use Clorox to bring the FC up to maintenance level and add enough CYA to get to 60ppm. Then start your SWG.

12. ## Re: Calculating pool volume question

HI jojo4A ~

I have an IG octagon pool and have been playing with gallon calculations because using circle dimensions don't give me numbers that correspond between my test results and pool calc numbers.

Circular pools use diam x diam x ave depth x 5.9
Rectangular pools use diam x diam x aver depth x 7.5

I have used both. Mine is 22 ft across flat to flat.
I've also used the halfway point of both.

Here's a site I just found: http://yourdallashandyman.com/how-to-ca ... your-pool/
It uses diam x diam x ave depth x 7.3 for grecian pools to compensate for the corner difference.

13. ## Re: Pool build in Alabama - Help with calculating gallons.

I have merged the two thread asking the same question...How to calculate gallonage. It is very confusing to ask the same question in two different posts.

14. ## Re: Pool build in Alabama - Help with calculating gallons.

If you are truly OCD, you can divide your pool into one-foot slices, and calculate the number of cubic feet in each slice, sum up the slices and multiply by 7.5 gallons/cubic foot. The number of cubic feet in each slice is equal to the area of the cross section of the slice since the depth is one foot. You can break the cross-section of each slice into smaller rectangles to get a better estimate. The slices can go lengthwise or cross-wise, so look at both to see which is easier to do. The end result is more accurate than a formula.

My old steel pool had a "V" shaped deep end, so I broke the pool into 3 pieces to do a precise calculation. Straight edges and 90° corners made it very accurate. In the pictured pool, you could do it by measuring only at two points, the end-wall and the center, both lengthwise. Calculate the cross-section for the center, and multiply by the distance between the two inside corners. Then use the average of the cross-section of the center and the end-wall and multiply by the distance between the end-wall and the inside corner and multiply by two. The cross-sections will be formed of several triangles and rectangles, but the result will be quite accurate.

15. ## Re: Pool build in Alabama - Help with calculating gallons.

Originally Posted by duraleigh
I have merged the two thread asking the same question...How to calculate gallonage. It is very confusing to ask the same question in two different posts.

Sorry for the confusion. I really appreciate your help. I am learning so much!!!

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