Normal solar water heater system to heat water can be classified into four principles, which allows them to adapt to individual requirements and situations.
Passive principle. It is used that the hot water due to its lower density rises by itself to the tank (thermosiphon principle). It does not require a pump, but the water tank must be placed above the solar collector to collect and store hot water.
Active principle. Unlike the previous one, in this case, a pump is used to move the hot water, and a controller turns off the pump if the temperature in the collector is lower than that in the solar water heater system tank (for example at night). It has the advantage that the tank can be placed anywhere, for example in the basement, while the panels are mounted on the ceiling.