Pool Size (Capacity) Estimation

[nefretrameses]

You can estimate surface area by measuring the number of gallons to raise your pool 1 inch. Requires a calm surface. Mark the current and desired level like on a skimmer I r piece of tape. Put the fill hose underwater. It shouldn't take a great deal of time, so maybe restrict other uses during the fill. Surface area = (Gallons to raise 1 inch x 12) /7.48 or Gallons x 1.604. Multiply surface area by average depth. Use a string with a knot tied every 1 or 2 feet. Pull the string across the length of the pool and use Doc's pole/yardstick to measure at each knot. Attach a small level with rubber bands to make the pole plumb. Add all the depths and divide by the number of measurements. There are other average depth estimating methods depending on the shape of your (pool's) bottom. Like shallow depth + deep depth /2. I was able to estimate my pool's gallons and confirm my result with expected response to chemical additions.

[washburn1445]

Exactly. But if you get too small, it will probably be hard to maintain equal squares throughout the measuring process.

I was just going to hang a lot of strings across the pool--I told the kids it will be like an archaeological dig. Haha.

You can estimate surface area by measuring the number of gallons to raise your pool 1 inch. Requires a calm surface. Mark the current and desired level like on a skimmer I r piece of tape. Put the fill hose underwater. It shouldn't take a great deal of time, so maybe restrict other uses during the fill. Surface area = (Gallons to raise 1 inch x 12) /7.48 or Gallons x 1.604. Multiply surface area by average depth. Use a string with a knot tied every 1 or 2 feet. Pull the string across the length of the pool and use Doc's pole/yardstick to measure at each knot. Attach a small level with rubber bands to make the pole plumb. Add all the depths and divide by the number of measurements. There are other average depth estimating methods depending on the shape of your (pool's) bottom. Like shallow depth + deep depth /2. I was able to estimate my pool's gallons and confirm my result with expected response to chemical additions.

Interesting. I found one the earlier planning sheets from the pool builder today (will be trying to contact them. I kind of doubt I will get anywhere, as I tried before and they were unresponsive), and it looks like although the pool is "free-form," they had planned the longer length to be 35' and the shorter one by 25' (the lengths being perpendicular to each other). I also know now the deepest part of the pool is 8' and the shallowest is 3'. The one complication is that there is a small "wading pool" section that is <1' deep (the previous owner of the house had a one-year-old and was planning to have another baby). As it will be easy (easier) to find the actual volume of that part of the pool, I presume I can just subtract that from the "surface area" approach.

[nefretrameses]

Exactly. I assume that the pool bottom has the same depth across the width of the pool at a particular point along the pools length. My pool has a 3 foot shallow and 6 foot deep end. Average depth (deep+shallow/2) = 4.5 ft. When I measure every foot , sum and divide by the number of measurements I got 4.1 feet. That's a 1200 gallon difference - about 10%. I also have curved corners where the bottom meets the sides. Its about a 2 foot radius, so I figured the surface area of the curved triangular area ((4x4)-(2x2x3.414))/4). Think of a circle inside a square of the same size. Multiply this area by the circumference of the pool to get cubic feet and multiply by 7.48 to get gallons. For my pool this adjustment was 51.5 cu. Ft. And 385 gallons (a subtraction). You can adjust for steps, swim out and other areas like yours in the same way. For my 13,000 free form pool it took 277 gallons to raise 1 inch - about 30 minutes with a garden hose. Being off ( of raising the water 1 inch) by 1/16th equals a 6.25% error - about 800 gallons. You can increase your accuracy by adding 2 inches, or 6 and adjusting the calculation. Don't know if its possible or desirable to lower the pool below the wading area then add 1 inch.