Copper coil solar water heater, we also called Pre-heated solar water heater. There is 25meters long copper coil inside the water tank. It combined the heat ex-changer（copper coil）copper coil into the non-pressure system So if use copper coil solar water heater, hot water can go out with high pressure and people can get clean, fresh and instant from copper coil. But the price is much lower than pressure system.
Not only there is much less risk for corrosion and scale deposit if use copper coil solar water heater, but also the water can be heated rapidly and can get more hot water than capacity of the water tank.