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High Pressure and Low Pressure Systems
The pressure of the water determines the type of overall system you require.
If ‘high pressure’ water comes out of your tap, you will need a ‘high pressure’ solar water heating system. If the water flows with no pressure, only using gravity, it will generally be a ‘low pressure’ system.
Most homes with an existing electric geyser will require a ‘high pressure’ solar water heating system.
Lower income homes that have no existing hot water boiler are generally fitted with ‘low pressure’ solar water heaters.
High Pressure Types
For the consumer the variety of choices to be made may be confusing. The first question is whether the homeowner is happy to have the complete solar water heating system sitting on their roof. This will include the tank and the solar collector, frame and accessories. If the answer is “NO” a split system will be required, where the tank is inside the home (generally in the roof) and only the solar collector is on the roof.
There are numerous configurations within high pressure solar water heating systems. Indirect and direct, split and integral, pumped or thermo-syphon are the main ones, but unless one is interested in the inner workings, the differences are not that significant. The important questions, other than cost and efficiency, is whether the system has electrical back up (most do), and whether the system can operate in a non-coastal area and is therefore freeze resistant.