Yes they are different pipes to connect to, and there really is no good way to add a Y fitting as one is in front of the tire, and the other is behind.
On mine, I added a black tank flush. That way I can flush the tank and hose before moving the hose to the grey. I have only used the trailer one time so far, but it worked great. Here are a few pics.
Here is a link to the thread with my mods on my 177LHS.
http://www.keystonerv.org/forums/showthread.php?t=26505