33feet, I like your construct! We don't have the space to put up solar panels anywhere near the pool but we could easily manage a box such as yours. How long are your hoses? How many 30 minute cycles do you run? Does the box have a solid top under the black vinyl? On second thought, probably not . . . the vinyl is your solar collector, right? Is the box tilted to allow rain water to drain off? Any chance you could post some photos? If so, please e-mail them to poolforum at gmail dot com with reference to this thread and Ben will post them.