Gravity systems do not require a pump and simply rely on a mechanical float valve or DC Solenoid Valve to open and close as the water level rises/falls. In this instance, the ATO reservoir must be mounted above the water line in order for water to naturally flow downhill into the sump or aquarium.

★ Note: For DC Solenoid Valve, the working pressure is between 0.02-0.7 MPA. The distance between the water inlet of solenoid valve and the bottom of ATO reservoir must be higher than 200 cm (6.5 ft). Otherwise, the solenoid will leak due to insufficient inlet water pressure.

● 1 inch of water is ~0.035 PSI.

● 0.02MPA is 2.9 PSI → 2.9 PSI = 83 inch (200 cm)