One of the toilets in the house has an intermittent issue with air
Occasionally, when just sitting there unused, a single bubble of air
will 'blurp' as it reaches the water surface in the bowl. It might
happen once or twice in a day, or as many as ten times (possibly
more). The toilet has zero problems as far as function go.
I think we first noticed this last year but it went away after a
while. It returned a couple months ago.
I've read that a clogged waste vent could cause this. I've looked in
them (from the roof) an don't see any blockage. The other toilets in
the house don't have this problem either.
All that could cause that is air being forced up the sewer pipe. Examine
your plumbing. That would be gas bubbles from the sewer or septic system
that are bringing that gas into the house. Not a good thing.
Thinking out loud (and I know that's dangerous): there's no pressure
in a drain line. They are designed to run at atmospheric pressure.
So there is no way a bubble gets forced backward through a trap unless
something temporarily increases the pressure.
My guess would be nothing wrong with that toilet, but something wrong
elsewhere in the system. Perhaps your wash machine line, dishwasher,
etc. Something else is producing system pressure that doesn't escape
through the roof vent and goes to your toilet instead.
hmmmm... toilet was added later to original plumbing and is not close
enough to a soil stack vent? toilet is on basement floor and was
added on top of a floor drain with its own trap (double trapped)?
clogged traps where leaves block the sewer inlets for roof rainwater?
I have one which exhibits that sort of behavior, but it is more often
than not. I'm not shocked though. It was installed as an after though,
above a slab with very little pitch to the drain pipe. It does work
surprisingly well though, it flushes solids better than others that
seem to have everything going for them, though watching the event it
seems unlikely. It farts then swirls then slowly starts to the bottom
only to gurgle when it gets there, but somehow in all of that the
payload gets delivered.
Or, the pressure outside of the house could be greater than the inside
of the house. If you have a newer 'air tight' house, and you use a
kitchen fan for example, to pump air out of the house, then you might
create enough of a pressure difference to suck air in through the
toilet... Just a thought (do you feel wind every time you open the
to answer some questions:
- it is not a well-sealed house. built in 1953. lots of drafts.
- nothing else is happening when the bubbles occur. no other devices
connected to water or sewer operating.
- this toilet is in an original toilet location in the house and is on
the first floor.
- admittedly i can't see all the way down the vent. perhaps i should
try better with a good flashlight. there's certainly nothing within
the top 5-10'.
Since you claim that nothing else is happening in the house at the
time, and as VC says, the only thing that can cause this is "air being
forced up the sewer pipe", (similar to my explanation) my next
question would be:
How are the pipes outside your house connected to the sewer? Where I
live, my neighbor's waste pipe and mine are connected to a wye just
before the main sewer. From there a single pipe goes into the main
sewer. I don't know if it's possible, but maybe a blockage after the
wye forces air back in *your* pipe when your neighbor flushes.
Have you discussed this issue with him? If you're friendly enough, you
could call them right after the next bubble and ask them if anyone in
thier house just took a dump.
re: "admittedly i can't see all the way down the vent. "
I'm not doubting this as a cause, but I'd like an explanation as to
how a clogged vent would cause this symptom.
How would a clogged vent force air back up through a toilet?
A clogged vent means there is no means for the pressure in the pipes
to equalize with the pressure of the house. Gas buildup in the pipes
would create added pressure, and eventually it would escape -- say
through the toilet.
But, if this were the case, then that bubble would likely be very
smelly, and the OP didn't mention smell. Also, it would be more
likely to occur when another toilet was being flushed etc, again,
inconsistent with the OP's description... so the bubbling toilet is
still a mystery.
I don't think you can use smell to confirm anything. If the plumbing
is vented properly and in working order any atmospheric pressure in
the drain pipe should be vented out the vent at the top. It should
not be forcing air back out of the toilet. It's an old house so
either improperly installed plumbing or a clog could be the
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