normal drain action, or.....?

I've got the master bath gutted and a rag in the toilet drain flange to block the gas. The wall behind the toilet is common to the main bath, where another toilet sits exactly opposite the one in the master. The stack is in the wall between them, and both connect via a very short run of 4" pipe. Both have a 12" rough.

I've noticed over the last few days that the rag in the open drain seems to be "sinking" into the drain, but kind of ignored it. Yesterday I was in the bath and happened to be looking at the drain when someone flushed the toilet on the other side. The pressure actually pushed the rag back out a couple inches before sucking it back. I noticed just a little water oozing around the top of the rag.

I would certainly think this is not desirable, but is it a problem? The toilet on the other side is a Toto Drake, so I know it's pushin that water (and content- ) out the pipe pretty quick. The house is on a slob so making a change is not particularly easy.

comments? should I be concerned?

TIA!

-art-

Does the other toilet connect to the stack just above the "rag stuffed joint"?

Doesn't sound like a problem to me. When the toilet flushes, it sends a pretty good slug into the main stack, compressing air in front of it... a light plug like a rag is going to pulsate a bit as the air passes it....

Keep an eye on that rag.... don't want to lose it down the pipe and end up fishing for it.... As for the house being on a slob....... well, hose him down and send him on his way...

Do not forget about your rag. I did that once and did not remember untl after many test flushes. It was a nightmare.

That's pretty normal.

The rag will wick water that's in the pipe.
When things are back together, it should be fine.

thanks for the responses all.

the two toilets are "back-to-back" with the drain stack in the wall right between them. it's a slab floor so I can't actually see the connection, but I have to assume that they on the same level - connected with a double-y most likely.

I suspect that with the old toilets I might not have noticed anything on the flush, but this new Drake really packs a punch - which is why it does the 900 grams.

just goes to show that with some things a little knowledge is more confusing than beneficial. kinda like the difference between being a good sausage cook and one day deciding to check out how it's actually made....

ps - I'm thinking I can solve my 'problem' by just getting a bigger rag that fits nice and snug (as in tight!) at the top of the flange.