Sonic Boom When Flushing Toilet

[mlaurens1213]

I own a 3 story apartment building with one unit on each floor. A single vertical PVC drain pipe serves all three bathrooms. I live on the first floor, and the drain pipe is within one of my bedroom walls. The problem is, every time a toilet on the 2nd or 3rd floor is flushed, it creates what is essentially a mini sonic boom in my unit. It is easily heard in the living room which is outside the bedroom, but inside the bedroom, it is of course very loud. I couldn't believe the level of noise when I first moved in - my jaw literally dropped. The noise is hard to describe, but thunderous is the best adjective. It's like a thunderous waterfall. It only lasts 2-3 seconds as the water surges past my unit.

I also had some work done on my bathroom shortly after I moved in, during which my section of drywall was filled with a really dense, sound insulating material on both sides of the drain pipe, but it only reduced the noise by maybe 10%.

I've searched all over the internet but haven't seen anything like my situation. I know that PVC drain pipes are expected to be noisy, but when reading about the noisiness of PVC drain pipes, I've never read any descriptions that sound as bad as what I experience multiple times a day.

I'm wondering if maybe the drain pipe is not perfectly vertical, but instead has some kind of bend somewhere, and the bend is causing the acoustic effect. Or if there might be some other characteristic of the pipe that is causing it. My understanding is that the top of the drain pipe extends to the roof and vents to the outside air - is it possible the noise is caused by roof vent being substantially blocked, and that causes an acoustic effect? To be honest I haven't checked the roof vent.

I'll include a mock-up schematic.

 

[Twowaxhack]

You could have the pipe replaced to cast iron or wrap the pvc with sheet lead.

 

[MrInfoPhilly]

a couple things., Solid Core PVC is quieter., which has red letters., You may have Drain pvc pipe., which is even louder.
2.) The quiet solution would be to replace with Cast Iron for the vertical Stack., that is 1 solution.
You can add a velocity break., have a plumber add an Offset in the vertical stack somewhere in the 2nd Floor. Its loud because you have freefall in thin PVC pipe.

Twowaxhack gave the correct answers
Either use Cast Iron., insulate the existing piping., or add offsets...
I'd personally swap about 20ft 2nd floor ceiling below the toilet inlet to the first floor with Cast Iron., and be done with it. Cast Iron is used in hospitals for the Waste because its QUIET.