Toilet Burping and Gurgling, Affecting Other One

[vfrkids]

We always liked this toilet for it's strong and quick flush (American Standard Chamption, I believe, with a 4" flush valve), but now we consider it a problem especially seeing the water 'burping' up before going down, and it causes a similar burp and sucking of some water from the the adjacent bathroom...

When this toilet flushes...
https://youtu.be/_iQReCCjCt4


...this happens in the other one
https://youtu.be/TK7i3feK6dM


We just remodeled the bathroom adjacent to this one and the new toilet (wall-mounted) gurgles a bit and has some water sucked out when the American Standard is flushed. The bathrooms are adjacent but the toilets are on different walls and not directly back-to-back. The American Standard is in an updated bathroom done before we bought the house.

This behavior was happening before the new bathroom remodel as well but it wasn't pronounced or particularly problematic; now the gurgling in the new bathroom is louder and the wall-mount toilet bowl has less water to begin with, so we definitely want this addressed.

Yesterday the plumber snaked all the vent pipes in the house and found a bit of leaves but nothing that made any difference.

The new toilet and one other in the house work fine and do not affect each other when flushed

I realize this is a trial-and-error type of problem and I would like to get it resolved in the smartest and least costly way (hence my posting here...)
Appreciate any advice.

 

[Mr_David]

Maybe just Me but I had to read your post a few times to clarify.
The A.S. is the existing water closet and I am going to presume it is floor mounted .
The new water closet is wall mounted.
The gurgle was occurring prior to replacing the wall mounted WC but not as severe.
So the only thing you changed was the wall mounted WC ?

If that floor mounted WC was added to the system improperly it is highly possible you have a venting problem.

Maybe with a line camera you can map out how it's plumbed and vented.

The new wall mounted WC is probably more efficient than the old one.
The weir and is shallower than the old WC and is less resistant to the air back pressure from the other toilet.

Pull the AS WC and set it up on some blocks outside.
Flush it.
Because it is not restricted by the connection to the drain it most like will not burp back on itself. This would confirm it is not the WC causing the problem

 

[vfrkids]

You summarized perfectly, thanks.

Plumbers will be coming back to try to figure it out, but wanted to be as knowledgeable as I could to speak intelligently on the issue.

The AS flush is quite fast and strong - does it make sense to think that replacing the flush valve with a regular flapper (smaller than 4" if possible), could slow/weaken the flush enough to alleviate the issue despite possibly less-than-adequate venting?

 

[Mr_David]

You won't be able to replace the flush valve with a different type.
Good luck!

 

[vfrkids]

You won't be able to replace the flush valve with a different type.
Good luck!

in that case - and sorry to bother you further - would I have to replace the entire toilet or could I just try a different tank?