http://www.terrylove.com/forums/show...light=disposal There is a drawing in this thread that may help you.
I have this annoying problem. Went to local DIY store, no help. Plumber here to do bathtub looked and he was stumped.
Here is what I have. As you face the sink to the right is the under counter dishwasher. Then I have a double sink. The sink closest to the DW has a disposal on it. Then I have a secondary sink to the left of the main sink. Standard kind of double sink.
Okay when I put stuff down the disposal side and turn it on with water running, At initial turn on the second sink gets a flow of whatever was in the disposal. It, the sink gets nasty looking.
A straight pipe runs to the secondary sink which has a pipe going down to the trap then out. The secondary problem sink does have the flapper do hicky built into the PVC to guide everything down, but it doesn't.
Nothing is blocked. All pipes taken down and checked. Dishwasher runs fine, water runs fine, only when I first start the disposal do I get the back up.....
Any help would be appreciated.
Can you post a picture?
Semi-professional plumbing designer
Enjoying life in SW Florida
I would suspect that your "flapper do hickey" is installed upside down.