Epson SQ-2550 User Manual page 194

Follow these steps to replace the ink cartridge.
1. Open the ink cartridge compartment cover located at the
front of the printer by pressing once on the area marked by
the three grooves. Then carefully remove the used ink
cartridge from the printer.
Note: On one end of the cartridge is an ink indicator lever
that registers whether the cartridge is full or empty. When
replacing an empty cartridge with a new one, you can check
this lever to avoid confusion. After replacing the cartridge,
dispose of the empty cartridge immediately since it cannot be
refilled.
Replacing the Ink Cartridge
Maintenance 6-7