HP Ink-jet printers work by jetting droplets of ink out of very tiny holes in the ink cartridge onto your paper. When you are done printing, some droplets may still reside on the head of the print cartridge. In order to remove the residue on the ink cartridge, your printer will move the cartridge head over the service station where it will drag the head over a wiper assembly which will wipe any excess ink or sludge off the cartridge head and into the spittoon. Inside the spittoon may be a sponge that helps to soak up the ink so there is less chance of a spill while moving the printer.
Remove the output tray by lifting it up and then pulling straight up until it comes out.
Take off the stopper assembly by fully extending it and then pulling it toward you while lifting slightly.
Remove the clean-out trough assembly by turning the knob located in the middle of it, counterclockwise. Pull the trough assembly straight out toward you after you have turned the knob until it is completely out.
Take off the access door on the top of the printer by lifting up the access door and removing the two T-20 screws that are holding it in. Lift the whole access door assembly straight up making sure it doesn't catch on a different part as you lift it.
Use your flathead screwdriver to pry open the snap that holds the right end cap assembly onto the input tray. Lift the printer and remove the cover making sure you unplug the two wires that are plugged into it.
Locate the service station assembly on the right side of the printer and remove the two T-10 screws that are holding it in. Slide the service station assembly backward to remove it
Take apart the service station by removing the two screws located on top of it. Inside you will notice a sponge and the spittoon.
Drain the excess ink that is in the spittoon and use warm water to clean it and the sponge. Make sure the sponge is completely dry before you reassemble your printer.