Solution to a bubbling toilet and sudden water level changes in the toilet bowl. Both indicate an air-venting problem in the drain system.
By the DIY experts of The Family Handyman Magazine:September 2006
If you have air bubbles that rise up through your toilet bowl (except when it flushes) or notice the water level rising and falling, you probably have a clogged or improperly vented toilet. This is especially true when you have an appliance like a clothes washer nearby. Your drain
line is gasping for air.
When you pour
liquid from a can, you’ll notice that it
doesn’t flow evenly unless you have a
second opening for air. The same
holds true for plumbing. As water
goes down a drain, air is needed to
equalize the pressure in the drain line.
This is the purpose of a venting system.
If the drain lines in your home
have poor venting (as in Figure A, for
example), water rushing down the
drains will pull water from nearby
P-traps. The drain in the toilet bowl is
basically a P-trap. If the problem just
started, it’s probably a blocked drain
or vent that needs to be “snaked” out.
And since the water in the toilet is
dropping and gurgling, it’s likely that
the problem is near that area.
Unfortunately, a clogged or missing
vent is tough to fix, since it usually
requires breaking into the walls to
examine the drain system. Unless you
have plumbing experience, this project
is best left to a professional.
Venting in this system is
missing, or the vents
don’t open to “free” air.
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