Epson EPI-4000 User Manual page 146

Replacing the Ink Cartridge
Note: The ink indicator lever at the end of the cartridge tells you
whether the ink cartridge is full or empty. The lever is up when it
is full and down when it is empty. (The letters F and E are
embossed on the cartridge case.) Check this lever to avoid
confusing the old cartridge with the new one.
4. Hold the new cartridge with the triangle on top of it pointing
toward the printer as shown below, and insert it into the
compartment.
Maintenance and Transportation
5-9