Sorry to hear about your sewer connection problem. However I don't know
anything about how the 74's are configured. You may want to post a
question on AirstreamForums, there are lots of folks there that may have
some insight for you. Here's a link if you aren't already registered:
http://www.airstreamforums.com/forums/?referrerid=30
It's free & there's a wealth of knowledge within the
membership...besides, it's fun!
Good Luck ~
Shari :)