Working Principle:

This type solar water heater provides main pressure pre-heating via a high efficiency copper coil heat exchanger  with the solar collector tank.

Rater than using the water in the tank directly, as the non-pressure does.

When water flows through the coil it absorb heat from the water inside the solar tank. The solar tank therefore is a thermal store and amount of

Water you can draw isn’t restricted to size of tank.

There is no water entering such kind of collector so that it can avoid corrosion and rust. Pre-heating solar water heater can be connected directly with pressure water pipeline.

So it can be used as high pressure system.