Low water level in bowl with strong siphon

[Eval]

hi,guys! I am new here and found this great forum by fixing the low water level in my toilet. I found this page( https://terrylove.com/forums/index....ns-minutes-after-flushing-has-completed.3066/ ) first and inspired me to consider a clog.But no clogs in my drain pipes. Problem still hasn't been solved, so I need your suggestion how to fix it or just buy a new toilet?

Background
I live on a apartment at 23rd floor, this building is 28 floor and 2 years old. Main pipe is two 160mm diameter PVC pipe. I ask my neighborhood, main pipe seems to be good. Toilet works well until last mouth.
last mouth,my toilet's water in bowl will not refill up after flushing, this low water level maybe caused by the non - stop siphon and the drainage is smooth.I tried to replace a new wax flange, using a pipe snake to shoving, but not works. Finally, I removed the wax flange, the water can refill but still drains, much better,but water level still low. And no flange maybe leaking at bottom and smell terrible. So I don't know how i can do next. Still using snake to shoving clogs? or get new toilet? I need your helpful suggestion, many thanks.

 

[Reach4]

Interesting... removing the wax ring made the toilet operate better. Sure sounds like a venting problem. But even then, the operation was not really right.

Your drawing shows a trap under the toilet. The trap for the toilet is part of the toilet itself. I expect there is no trap under the floor for the toilet.

So you could measure the pressure in the drain lines with a manometer. https://terrylove.com/forums/index....b-drain-stumped-3-plumbers.76371/#post-560269 described making a very inexpensive open air manometer.

Would your problem be made better with a new adjustable fill valve where you could increase the refill rate? Maybe. Would a new toilet improve things enough to deal with the apparent venting problem? Maybe.

Would adding an AAV under the lavatory admit enough air to help this situation? You don't show a lavatory in your diagram.

I think I would lean toward a new toilet.

 

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[WJcandee]

That sure seems like an awfully-small water spot to start with. How do you know that's the normal settle-level? Have you tried slowly pouring a couple of glasses of water into the bowl after shutoff to see if it can settle higher. If it continues to drain down after shutoff to the point you show, then it seems to me that it's either: (1) the toilet is very much not level front to back or (2) it is being siphoned b/c there's no vent on that branch. Does it always do this or just when you're running the washing machine?

An AAV would be a relatively-inexpensive thing to try to see if it makes a difference. Is there no sink in the bathroom with the toilet? You show the floor drain and a washing machine, but no sink? If there is a sink beyond the toilet from the stack, then an AAV by the sink (like Reach recommends) would be easy-enough.

BTW, I join Reach in assuming that there's no trap under the toilet. The toilet's trap is in the toilet itself; toilets are installed over a closet bend that contains no trap, which is why you plug the hole with a rag when you have it off, to prevent sewer gas from coming into the room. (There is basically zero sewer gas that comes up in our house in the country when I pull a toilet; in our City apartment, within 5 seconds it's almost impossible to breathe.)

You need the wax ring to keep the sewer gas from coming into the room. So you have to put it back right away.

Also, in a 28-story building (rental? condo?), normally you're prohibited from messing with the plumbing, by whatever agreement you have with the building owner or condo association and usually by local law. If this is a sudden event, I suspect that there is a whole or partial blockage of the main vent or similar issue.

Is there a reason not to contact the building services to complain about this and get them to fix their own issue with the building plumbing. Putting in your own AAV seems like a lot of self-help to have to do in a multifamily building.

 

[Jadnashua]

Does the bowl water level rise, then drop while refilling or after the flush?

As suggested, try SLOWLY pouring some water into the bowl to see where it stops rising and see if it stabilizes (may take a minute or so after you stop pouring). If it rises, and stays there, the first thing to look at is in the tank (assuming it has a tank!) and look at the hose coming out of the fill valve that goes to the overflow tube...that tube must not be blocked, and must point down the overflow, AND, must not be pushed down inside of the overflow tube...it should have a clip on it holding it up above the water level so there's an air gap. That is what refills the bowl.

If they used the wrong fitting and you have back-t0-back toilets, when someone on that other toilet flushes theirs, some can come shooting across into yours and rock the water level. That can make some of the bowl water slosh over the weir (the outlet) and down the drain, lowering it.