In the first picture below (please try to ignore my abuse of expanding foam) the black 3" schedule 40 pipe on the right is the main drain line for the second floor (toilets, showers, sinks). The white drain line connecting to is from the kitchen sink and dishwasher.

The smaller 1-1/2" pipe going to the left is a vent. It goes to the left, then down, then to right; the laundry sink (and thus the laundry machine) drain into it at this point - see the second picture - and it then connects to the main drain line with T.

As you can see, it's leaking. This leak is because He Who Shall Not Be Named drill a bloody hole into it, seemingly with a hole saw. He then shoved 1/2" PVC drain line for the furnace condensate into it, and slathered some unknown gray goop over the whole mess.

It has apparently had a slow leak for years, and rotted out parts of the separating wall that was near it. When I removed the wall, the condensate drain line popped out. Thus, the Very Rapid Leak began when using the laundry sink or washing machine. All I had on hand was some adhesive flashing, which obviously didn't work very well.

Can I connect the vent to the kitchen drain line at the top instead, and if so, how? In an ideal world, I could find a 2" clamp on right angle, with a 1.5" T connection built in.

Having this vent pipe connected up there would make fixing up the mess below a lot easier - not to mention, it previously butted up against the separating wall so that the former owner cut out a section of drywall to allow it to fit, and then .. painted the insulation.

I was thinking about using the rubber PVC couplings with screw in clamps to do so, at least temporarily. Long term, the whole setup needs some work - the Y going into the 3" pipe on the right has a little crack at the top, hence the black sealing tape around it, and the drain line from the kitchen (the white pipe) has a slight incline rather than decline, and I'd like to replace that rubber PVC coupling.

Not to mention removing the expanding foam. ;)

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  • 1
    On the other hand, maybe this is the time to do it right - replace the broken Y in the 3" drain line, fix the line and slope coming from the white pipe..
    – negacao
    Jun 29, 2023 at 12:38

1 Answer 1


The washing machine drains into this sink (which drains into the line in the second picture).

As far as I can tell, code requires a vent pipe very near any laundry drain, if not directly connected to the stand pipe.

So I believe the answer is no, I cannot simply change the vent to connect to the upper drain lines - if I do so, I must add an additional vent, or at least air inlet valve, near the laundry drain.

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