I have a single hole sink with the dishwasher drain going into the disposal
The wall plumbing has the P trap coming from the disposal into the wall drain. There is an air vent with a P trap entering the wall drain directly BELOW the disposal p trap in the wall drain.
I'm constantly getting back flow from the lower vent trap. Originally there was a double sink and the dishwasher drain hooked into this vent trap. I'm wondering if this vent trap shouldn't be above the disposal trap since I now only have a single sink and there isn't a vent above the disposal trap. It seems it would have gotten air from the second sink before and now there is no air above.
Does this sound logical?
When I get back flow it's when I run the disposal and there is some water running.
Best Answer
My question would be how do you keep water in the trap for the vent? , I would add an air admittance valve then you won’t have to worry about water in the trap and won’t get back flow through the vent. The air admittance valve on the open end of the pipe.