Both the solar panels and tank are mounted on the roof.  The panels are located just below the storage cylinder and water rises into the tank through a principle known as natural thermosiphon.

 

Advantages:      Usually the most cost-effective system to install.

Provides water at mains pressure or low pressure

Has no moving parts, has the  highest efficiency

Can also be used as a waterproofed gravity -feed tank for wood heater backup in winter

A good option if a position for a ground mounted tank cannot be found.

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Disadvantages: Roof needs to be designed to withstand the combined weight of tank and water.

​May not be aesthetically pleasing to some