Re: Solar panels on a south'ish facing verticle wall *update
Well they were OK for limited heating, but mine were not in coils they were just thrown around the roof and overlapping and would not drain so when not on they would get really hot and then when it got cold places would split and I was continually having to fix leaks ... just annoying. Since I need to get the roof re-coated, I ripped the whole setup off the roof and found a used set of panels on CL.
Depending on what you are trying to accomplish and your sun angle to the panels, the recommendations I have seen are a heating area or 40%+ of your pools surface area. Currently you have around 8 sqft assuming your tube is 1" in diameter and that is not going to give you a lot of BTUs (there are other posts here that discuss this in great detail). I think when you start looking at the number of coils needed to get to an adequate surface area, if quickly becomes apparent that it is cheaper to just buy the panels.
2500ft of tubing would give about 200 sqft if it was laid out well and probably would be adequate for average pools here in AZ to extend the season some (in the summer we do not need to run it at all as the water gets too hot). My pool have a pretty large surface area and the deal I found for the panel ... I figure I may as well put them all up and see how long a season I can get (especially since I do not like the hassle of a cover ... although I may get one as well).