How to Clean Waste Ink on an iP1500

Unplug the printer from its power source.
Lower the front cover on the Canon iP1500 by pulling on the top of the front lid of the unit. Pinch the hinges in toward one another to release the front cover from the printer and remove it entirely.
Near the hinges of the front cover of the unit, you will see two screws. Use the screwdriver to remove these and place them in a safe location.
Turn the printer upside down. At the back of the printer, you will see a tab on each side. Press down on these tabs to begin to release the base from the upper portion of the printer.
Turn the printer right side-up again and locate the pair of tabs at the back of the printer where the paper feeds into the unit. Pry these out with your finger to release the top of the printer cover from the base. Lift the cover off the printer and set it aside.
Turn the printer so that its front side is facing you. On the left hand side of the unit, you will notice two prominent silver screws. Behind these on the inside of the panel they attach to, is a single black wire. Carefully pry this wire out of its channel, but be careful to avoid breaking the solder joint between the wire and the motor it is attached to. Unscrew the two silver screws.
Turn the printer so that the opposite side faces you. When facing the front of the printer, this would have been the right hand side. You will notice a plastic grid with a single silver screw slightly above and to the left of this grid. Remove this screw.
Face the front of the printer again. Slide the printer ink carriage to the left so that it is positioned in the middle of the printer. There is a metal track just below the carriage that extends for the length of the printer. Remove the screws holding the track in place.
Look at the top of the unit. You will see the circuit board attached to the front of the unit. There is a series of three blue cylinders on the circuit board and a white wire near it. Gently pull this wire out of the circuit board harness. Directly below the blue cylinders you will see another screw. Remove this screw.
Pull upward on the unit to loosen it from the printer, but do not pull it all the way off the printer. Remove the paper support tray at the back of the unit by pressing the tabs you find at the base of the tray. There is a spring attached to the back of the tray, so use care when removing it, as it will have to go back together again.
Look at the top of the unit. At the rear of the printer under the paper tray you just removed, you will see a silver screw. Remove this screw. Look down and to the right of this screw in what would be the four o'clock position and you will see two semi-transparent tubes running parallel to one another. There is one additional screw here. Remove this screw.
Look directly to the left of the semi-transparent tubes. Here you will notice two more silver screws. Remove these screws. The assembly connected to the semi-transparent tubes can now be lifted gently out of place. Beneath this is located the waste ink absorber sponges. Do not completely remove the assembly or move it any further than is necessary to pull the sponges out of the bottom of the printer.
Rinse the sponges with warm water to remove excess ink, wringing them out several times but being careful to avoid tearing. Allow the sponge to dry on a towel after it has been rinsed. You can use a hair dryer to speed up the drying process. After the sponges are completely dry, reinstall them into the printer and reassemble it in the reverse order from which you disassembled it.