Yes. Whoever is upstream would need to flush first and then as that poop would arrive under the downstream toilet if that person flushed - whoosh - they could collide in the main line. But gravity being what it is… there is little chance of a clog in the downstream toilet unless further downstream is clogged and then it could back up all the way back to both of you! But that’s what the siphon is for so it’s not actually going to come up out of your toilet… (Usually)
This is why in hotels you’re going to notice that all the toilets and the showers and the sinks form parallel runs all the way along the building. They’re all going to go down into a horizontal submain sewage tube (4"+) which is going to be pitched from one end of the building to the other. On the bottom (far) side of that is going to connect to the vertical main sewage line that’s going to go down vertically below the ground to the actual municipal sewage system as well as vent vertically upward out the roof.
schwim@piefed.zip 1 week ago
The reason it wouldn’t collide has something to do with an element of the network of pipes that I haven’t mentioned yet.
First, all pipes have a pitch or slope. That’s to ensure that the flow only goes in one direction. Secondly, pipe joints have a “sweep” to them, meaning the joint directs the the waste to go in a certain direction when intersecting another pipe.
The fitting in the image below is called a sanitary wye(Y). Imagine that your toilet or sink would be the source of the waste and would be connected to the 2” side. You can see which direction this would direct the waste and each connection to the trunk would be directing the waste in the same direction. For this reason, your flush would never collide with another, instead it would be like you both would be speeding along in the same direction and just kind of blend together if they happened to meet in the pipe at any time.
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Pressurized plumbing does not have these sanitary features, they just have hard angles with no sweeps because the pressure is what pushes the water to your faucet. Drain lines lack this force so everything is handled by pitch and flow guidance in the form of these joints.
terranoid@lemmy.cafe 1 week ago
So technically if I have the right fishing gear, I could turd burgle my apartment neighbors without leaving a trace? Like a poop ninja?
Doxin@pawb.social 1 week ago
People do this all the time accidentally with drain snakes. So yes.