I have contemplated a number of options of potentially lengthening the swimming season by at least a few weeks on each end, one of which I actually implemented. I made a pool cover out of PVC and 3 mil plastic, but I was only able to use it for one season, as it got torn up during the winter because it wasn't stored properly. I started remaking them the last spring, but didn't complete the task, and half of them got destroyed this winter as well. Needless to say, even though I think this is likely my best bet in accomplishing my goal of lengthening my swimming season, I cannot bring myself to complete the task again.
I have also considered the hose/sump method, but research (here on TFP mostly) has indicated that the volume of water that is heated is more important than how hot the water (in the hose) gets. In considering this method, though, I don't remember ever reading that the water should be taken from near the surface of the pool and returned near the bottom, since heat rises. Did I not read this because it is so obvious that it is considered to be an assumption, or am I not thinking properly about the (simplified) physics of heat transfer? Assuming the former, I also had this thought:
What if I redirected the water from my returns to the bottom of the pool using PVC? Then I would be effectively transferring the entire volume of the pool from the surface to the bottom every day. Surely there is a 1-2 degree difference in temperature between the surface and the bottom, isn't there? Has anyone thought of (and tried) this? Is this idea crazy, ingenious, or somewhere in between? As I said before, I have only a very simplified understanding of heat transfer. I simply know that heat goes to where there is less of it (which for some reason is generally up).
By the way, I have even thought about purchasing a pool heater, albeit not very seriously, as they are quite expensive up front and surely are not inexpensive to use either. I read here on TFP that the recommended brand is Raypak, but the recommendations for this product make me leery of buying one! Are these consistent negative comments accurate at all, or is this just a specific model that should be avoided?