I noticed that my washing machine drain may not be properly vented: There is just an ABS pipe sticking up behind the laundry. In the basement underneath, it just goes into a cast iron sewer line that's shared with the adjacent bathroom sink:
Here is how the pipe looks behind the laundry:
Here is how it looks from the basement:
You can see how the ABS pipe is connected to the cast iron pipe via a wye fitting (but no further connection). On the left end, the wye for the bathroom sink in my diagram can be seen.
Please note that the ABS pipe does not just stick up straight. As a matter of fact, it goes into the wall. Hence there is at least one elbow in the wall (indicated by the right angles in my drawing), but I do not think it's a p-trap: I tried sticking down a fishing tape with paper. I can clearly feel hitting an angle. Even when I push beyond the angle and then pull out again, it's bone dry. With a p-trap the paper would need to be wet, right?
Hence I believe this installation might not be proper.
On the other hand, in the 1.5 years of living here, I have never smelled sewer gas in this room. I also stuck no nose into this pipe and carefully took a deep breath: There is nothing that would smell like sewer gas.
Question 1: Does this require fixing?
Question 2: How can I best fix this without re-doing everything new?
One issue I see is that there is just not much room. Here is another picture that shows the ABS pipe sticks out not more than 1ft before going into the cast iron part:
But not just with the length, it's tight in general: There is not much room for a p-trap. There are conduits, water pipes and wires closeby and the pipe goes up between two wooden beams, so not much room there either.
