mathey said:
talked to my neighbor yesterday... his temp is 72, mine is 86
he said his liner is almost white now (12 years old)
Sorry if I seem skeptical but I think something else besides pool color is contributing to the temp difference. I don't think the physics can support that. Without solar, I doubt very much any pool could be 14 degrees wamer than another without other important factors involved. Pool water itself is fairly efficient at capturing heat. However, retaining the heat is dependent on other things such as a pool cover. Nightime exposure would ensure that most of the heat gained was lost each day. This hapens for me with solar panels when I do not use a cover. For a fair comparison, the following must be true.
Identical time exposure to the sun (# of hours and time of day) between pools.
Identical wind exposure between pools. If he gets more wind than you, his pool will be cooler.
Identical use of pool covers between pools. This is a big one. If you use a cover and he does not, that will make a big difference.
Identical surface area to volume ratios. The amount of sunlight captured is proportional to the area of the pool but the BTUs required to raise to a certain temp is dependent on the volume of the pool. If you have more surface area to volume than another pool, your pool will heat faster even with the same color.
Thermometers are working properly in both pools. I have seen too often bad thermometers.
The highest temp difference that I have ever heard of is 3 degrees for color change. I heard from several plaster installers not to expect anymore than this for a darker color.