sink drain vent?

[skippy102162]

Have a shower and incorporated the shower drain and sink drain together to empty into the gray water container or the sewer.  Do I need to vent the sink for more efficient draining AND is there a concern when hooked up to the sewer regarding odors if not vented?

[oldmoose]

There's a thread about sink vents on the General page. Lot's of info.
Moose

[tlhdoc]

Do you have trouble with your sink or shower draining?  If you don't, then you don't need to install a vent.  If you do have a slow drain, then a vent will help.  When draining into a sewer does water lay in your hose?  If so you will not have a problem with odors backing up into your PU.  If the hose is on a steady down hill, you could have a problem.  
 
I have a vent for my sink and haven't had a problem with sewer odors.  I have only had full hookups a few times.