I have an above ground pool, 20 x 16ft and 4ft deep. I am curious about the science behind why heated pool water comes in near the top, as opposed to near the bottom (where it could rise up through the cooler water and warm it).
Whenever we get into the pool, the top foot is warm, then it gets colder as you get towards the bottom (as heat rises!) Once stirred by a quick swim, it levels out but if you don't swim in it daily (stirring it up), the heater is fooled by the top foot of warm water into thinking it has reached temperature, when the stirred temperature is actually quite a way below what you want it to be.
When swimming on holiday in a complex pool, I also noticed the warm water comes in near the top.
Why is it designed that way? It doesn't seem logical.