I have a 23,000'ish gallon in ground oval pool & recently replaced my solar cover this year with a brand new cover. I have had the cover on for about 4 weeks 24/7, & the water temp is still in the mid 70's. My friend also has a solar cover on his in ground pool, & his water temp is high 80s. I should mention we live in NC.
My first year with the pool, when I had my first solar cover on, the pool water heated up very quickly to the mid 90s & felt like bath water; it was awesome. The only differences between that first year & this year are that I ran the filter 24/7 the first summer & it was freshwater cleaned by chlorine. I have converted to saltwater now, & run the filter on a timer, 4 hours on, 4 hours off. My friend, who has the pool with water temps a lot higher than mine, also has a saltwater pool, but runs his 24/7.
My question is, is my running 4 hours on, 4 hours off, the reason my temps are not rising? That is the only difference between my 1st year & this year, & my friends pool & mine, that I think may make a difference. My theory is, during the 4 hours off, the top few inches of water get heated up by the sun. Then when the filter turns on for the next 4 hours, it circulates all of that colder water underneath with the few inches of warm water on top, thus cooling that warm top water. Therefore, it never really gets warm. If I ran the filter 24/7 for a few weeks, the sun would penetrate the cover & heat the constantly circulating water, thus heating all of the water rather than just the top few inches. May heat more slowly, but it would heat throughout the entire pool, rather than just the top few inches.
Does my theory sound correct, or am I going mad?
Thanks for any help in advance!