It is very important to consider climate in solar pool heating design. Usually the system must be winterized by emptying the piping and collectors. If too much water is trapped in piping that freezes the water will expand as it freezes and burst the pipe. That pipe can include solar manifolds and solar fin tubes but not so with Hot Sun flexible fin tubes. They can freeze full of water solid every winter with no risk of damage because the flexibility allows expansion to accommodate the ice.  In many climates, for example a high altitude location like Las Vegas or Denver, it can get quite cold on a spring or fall night when you are wanting to solar heat your pool during the day. Even if it only gets down to 37F at night on a clear night you will see frost on your windshield. Your solar collectors are an even better radiator to the night sky, meaning there is a big spread between keeping collectors from failing if not emptied and pipes freezing almost solid under a sustained hard freeze. The flexibility of the Hot Sun absorber (the fin tubing that spans between manifolds) is critical in solar pool heating outside the warm coastal temperate regions where solar pool heating is most popular.