A google search for Canon waste tank revealed some informative sites like
http://www.neilslade.com/Papers/inkjetstuff11.html
http://www.fixyourownprinter.com/forums/inkjet/15284
http://www.essex1.com/people/speer/canonink.html
http://www.uktsupport.co.uk/canon/canonidx.htm

You might have to do a little search yourself for the exact model of your printer.

Making an error might necessitate a call to a Canon repair center. The recommended procedure, of course, is letting them do everything - which might turn out more expensive than simply buying a new printer. It really is a shame.

Kees