The RX580 apparently has the access hatch to the waste ink tubing in the front right of the printer (looking at the front).

This picture:
http://www.continuousink.info/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=447&g2_serialNumber=1

...provides a decent indicator of where it is and what's behind it.
(Source: Jayman007 on CDCovers.cc forums)


UPDATE:
Confirmation that the tube should be disconnected from the left side of the trapdoor (which is where it connects to the internal waste tank).



Last edited by Martin on Thu Sep 03, 2009 5:52 pm; edited 2 times in total
_________________
Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680

Found a source for some more images on this score...

This one:
http://www.pcworld.idg.com.au/mim.php/prodid/4447/vid/0/angleid/4/resid/2
.. indicates that there is NO trapdoor in the rear but other images have indicated that the trapdoor arrangement in the front does exist.


_________________
Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680

Modification guide added to the OctoInkjet site:
http://www.octoink.co.uk/kb/questions/65/Epson+RX640


_________________
Printers: (Canon) MP500/830, MX700, iP4000/4200/4300/4500/5200, iX4000(A3) (Epson) C84/86, D88, CX6600, R285/800/1900 (HP) K550, K850, K5400, L7680