A:AnswerHi Lydia, The ink has different characteristics. 502 and 522 ink should not be mixed. Mixed ink may not work properly in your ET-3700 and may affect warranty coverage. Regards, Mark - The Epson Team.
A:AnswerOne is DYE the other is Pigment.
502 bottles will not fit on the 522 tanks, nor 522 bottles fit on 502 tanks.
I did read C/Y/M are both pigment, however the bottles still will not fit on the others tanks.