Why is my Epson Stylus Cx7800 leaving horizontal and vertical white lines when I copy a paper?

White lines appeared? In vertical or horizontal?
Vertically white lines : clog on head. Check nozzle & head cleaning.
Horizontal lines : error in linear encoder.

Common problem..

Check your settings for proper DPI (dots per inch) and also change the ink cartridge.. ensure it is cleaned and calibrated as well..

Clean your rollers or call a printer repair man.

Please make sure the scanner flatbed is clean.
You can also try to copy and see if it happens on copying.
If it does, then your printer needs servicing.

It is CLOGGED print-heads that cause the ink to _not_ be sprayed onto the paper, resulting in "white" horizontal lines.

Run a "print-head-cleaning-cycle", using the Epson software installed when you installed the printer.

Just go to Epson's website and you could download a copy of the drivers, and any other software that was on the cd.

You don't need to do head alignment, because it is for vertical banding in printout. Vertical banding can be minimized by disabling high speed option without doing head alignment. If your printout have horizontal white lines, do check nozzle and head cleaning, or you can minimize white lines by printing in best quality (photo).

Nozzle check must perfect for perfect output. There are tranversal lines at vertical straight lines that represent same point of head micro piezo. If tranversal lines no clog at all, but vertical straight lines not perfectly straight, the result not good (like horizontal white banding). Check it? Head aligment is for vertical banding. If your result is horizontal banding, you don't need to realign head. It's caused by some residual at the output of head sprayer. So, the spray of ink not straight to paper. Try to print with photo/best photo.

Clean the nozzles, align the print heads, turn it off for about an hour. You may need to do this twice, but it works for me.

Is there any debris under the printhead nozzle plate?