Water supply's pressure is too big, Water splashed out from the vent pipe while fill the water into the solar water heater before tank is full.
Solution: Adjust the water pressure to standard pressure.
Reason 2: Inlet haven't switch off till tank is full
Solution: Close the switch of inlet when the tank if full; use water feeder or controller fill the tank automatically.
Reason 3: Water feeder cannot switch off when the tank is full.
Solution: check the water feeder if the ball valve of the water feeder is inclined; change a new water feeder.
Reason 4: Electromagnetic valve of digital controller is not working it cannot switch off.
Solution: Close the water supply checks the Electromagnetic valve and controller.
Reason 5: The high water temperature produces the steam, the steam comes from the vent pipe.
Water is boiling, the boiling water come out from the vent.
Solution: it's normal at the summer or cannot use up the hot water always.