MISOL Solar Collector of Solar Hot Water Heater/with 10 Evacuated Tubes/Heat Pipe Vacuum TubeDuda Solar 30 Tube Water Heater Pool Collector Evacuated Vacuum Tubes HotDuda Solar 30 Tube Water Heater Collector 45° Frame Evacuated Vacuum Tubes SRCC Certified HotDuda Solar 200 Liter Water Heater Active Split System Single Coil Tank Evacuated Vacuum Tubes Pressurized and Non-Pressurized Solar Water Heater The tube has the air evacuated out of it, which makes it highly insulatednot too different from a thermos used to keep drinks hot. There are two types of Solar water heater or Solar Geyser systems:Pressurized Geyser. Non-Pressurized Geyser. Compact Non-pressurized Solar Geyser-Evacuated Tube Water Heater 17 rows · Non-pressurized Solar System. This is an open-loop thermosyphon solar water heater.