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Horizontal Solar Evac Tube?
evac tubes that can be laid flat or on their side. They are a flow through design not a heat pipe. They are what they call a u-tube because the water just flows in a copper u-tube inside the double wall glass tube. The evac tube just slips over the u-tubes after you are finished installing the system, they are nice looking and do not need minimum pitch but they canot be used with a drainback system.