I have one toilet (of three in the entire house) that bubbles when initially flushed. When the toilet is flushed about three or four medium to semi-large air bubbles emerge, then the toilet functions normally. I understand the basic design of a toilet, my thoughts go to the vent pipe. Any thoughts on "why" a vent pipe could/would become blocked & how to correct this?

Thanx..

OK ...been reading other add'l/similar posts.. I just got off the roof (single story, albeit high pitch roof to permit high interior ceilings) where the 1 1/2" PVC vent just took 25' of drain snake as fast as gravity could take it, with absolutely no resistance / obstruction... any vent stack shouldn't be 8-10' below grade.....

Anyone got a Plan B?

In my line of work, we come across all types of weird situations. I have seen things such as birds, squirrels, ect.. get into a vent pipe, and cause all kinds of trouble. Is there a cleanout on the drain? Is another plumbing vent clogged? sink? tub? they may all be tied together? Maybe try that.
www.restinpeacebugs.com

My first thought would be 1 1/2 vent? You should have a 4" vent for toilet. If the vent was throttled down in the attic below so the pipe is smaller though the roof. That will act like a plug all on its own. National plumbing code as I understand it requires a 4 inch vent.
Might want to look into that further.

nothing else appears to be affected... I'm going to go with a "rubber bladder drain cleaner on the end of a garden hose" thru the vent suggestion... I've already tried 50' of std drain snake that disappeared into oblivion..... (albeit retrieved... ) I've seen those work wonders... my take is if ya don't ask, you'll never get the "no schitt there I was...." answers... (... ummm... sorry Retired USMC MSgt.... )

'tis a 1.5" PVC vent... nothing around here has a 4" vent anymore/anywhere... nowhere on a 3000 sqft house... just a bunch of 1.5"er's..... same all around the neighborhood.... (20 yr old)

I think I would remove the offending commode and try pouring 3-4 gallons of water straight down the pipe to see if you get the same effect. Sure sounds like a venting issue if the waste goes down OK after the bubbles. The problem with snaking through the vent is that the problem may be where the lateral enters the verticle stack. In that case the snake proves that the stack is open, but the pipe from the commode to the stack may have a restriction.

There could be a bird nest in the vent. This has happened on numerous occasions

I had the same problem occur at my house with 1 toilet upstairs and 2 on main level.They would all bubble at various times. Thought at first it was a vent pipe problem. I tracked down the vent[s] which became 5 -3"vent. All end up in the attic due to a metal roof all had vent covers in place so no bird/squirrel nest. After 2-3 weeks i then experienced slowing drains. i ran a snake down a cleanout [ 2 of them 50 ft apart]toward the street with no blockage on the first . The second at the street hit paydirt. I called the city they came out and s***** their line it cleared my line and since then no more air bubbles?

I had the same problem with one of my toilets. It was a first generation water-saver type and it bubbled a couple every time it was flushed...did it ever since we bought the home. I rebuilt the toilet replacing all the innards, but to no avail. During a remodeling project the toilet ended up in another bathroom...the bubbles followed. The new one did not bubble so I decided it must have something to do with the toilet. It was a cheap model someone added to our 1950's home before we bought it. I eventually disposed of it. I have not seen any bubbles anywhere else in our home.

If you had a clogged vent stack, you should experience other bubbling sink drains and the bubbles would occur with or without a flushing toilet. There woulod also be the issue of the smell.

My home does have a single 4" vent on the roof, but that is because of its age and the fact that it is cast iron. It's a 1.5 story Cape and I could probably burn 30' of snake before the first cleanout in the basement. Most newer homes have 1 1/2" vent stacks depending on thrir service, and may have one vent for each water group. Sometimes it is easier to run separate vents than to try and collect them all into one big run through the roof. also, the 1 1/2" vents are far less likely to attract vermin tenants.

Are you on a spetic system? or municipal sewer?

Normal city sewer..... this is a vent issue... just have to work thru the fine points...

Do you have a cleanout in the basement or yard that is easily accessible, ie, one that you can open easily?

Look, I hope I am wrong for your sake, but I do not believe this is a vent issue.

You could open a cleanout or even the p-trap in the bathroom where the bubble toilet is, and you will most likely bypass any vent clog you might have. Therefore, in theory when you flush the toilet after opening a trap or cleanout, there will no longer be bubbles if it is a vent problem.

I will be VERY surprised if the bubbles go away.

Probably unrelated, but it drove me nuts:
We had an old toilet -- here in the South people call it a "commode" -- that seemed to fill upward before (maybe) flushing downward.
I noticed that there was very little water flowing down from the rim; instead all the water was shooting out the nozzle which helps the flow enter the pipe. But not having enough new water in the bowl, there was no siphon to "help".
I realized that all the small holes around the rim were clogged with minerals from the water.
I cleaned them by jamming a scratch awl into each one, "stirring" the handle around to break up the deposits. If I chipped a little porcelain, oh well, the thing wasn't working anyway.
This worked wonders!
Also, over the years, I have learned to keep both top and bottom of a wax ring dry during installation to get a good seal.
Good luck.

Hi, I'm a contractor in North Carolina. Code requires that a vent be 1/2 the size of the drain served, or larger. Yours should be a "Minimum" of a 2 inch vent, 3 or 4 preferably.
Either install a new vent, OR cut in a 3 inch mechanical vent (air admittance ). Sounds like your house was plumbed incorrectly.
And don't get me wrong: I do NOT like mechanical vents, as they need to be replaced. A VTR (vent thru the Roof) is the way to go.