Canon WS8400 Service Manual page 131

If all of the ink passages are opened (no ink tank is installed, the ink supply valve is opened, and the print head lock lever is opened) when an ink tube is
filled with ink, the ink in the ink tube may reverse-flow due to the difference in the water head, and ink may leak from the ink supply needle. Therefore,
do not open all of the ink passages at the same time when the ink tube is filled with ink.
c) Draining the ink manually
Step 1
1) Remove the right circle cover (L), right circle cover (S), right side cover, upper right cover, and right cover unit. Refer to DISASSEMBLY/
REASSEMBLY > Points to Notes on Disassembly and Reassembly > Outer covers.
2) Remove the ink tank.
3) Move the carriage over the platen. Refer to DISASSEMBLY/REASSEMBLY > Points to Notes on Disassembly and Reassembly > Opening the
caps and moving the wiper unit.
4) Remove the joint [1] for the ink tube unit and the joint [2] for the ink tank unit. Insert the ink-tube-unit-side joint [1] in the ink supply base having an
ink absorber [3] so that the joint is not disconnected accidentally.
5) Unlock the print head lock lever to allow the ink for all six colors in the ink tubes to flow simultaneously to the ink absorber [3].
Carriage unit
Step1
Step1
Print head
Step1
Ink supply valve
Step2
Joint
Ink supply mount
F-4-68
Joint
Step1
Step2
Sub-buffer
Chapter 4
4-31