Indirect systems rely on Glycol as the heating fluid in the system, for this type of system a special geyser is required that is able to transfer the heat to the water in the tank. Indirect systems are freeze resistant and are able to withstand adverse water conditions.
Thermosiphon systems rely on a natural process where the heat generated in the Solar Collector is transferred to the Geyser above the solar collector through a thermal process. No mechanical process or electrical system is required. Thermosiphon systems are highly efficient and require little to no maintenance.