Signs of Poorly Vented Plumbing Drain Lines

Solutions to a bubbling toilet or changes in the water level in the bowl.

Why is the Toilet Bubbling?

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 toilet bubbling problem is especially true when you have an appliance like a clothes washer nearby. Your drain plumbing line is gasping for air.

If you suspect it’s just a simple toilet clog, here’s how to unclog it.

Popular Videos

Why is the water level rising and falling?

Other explanations for toilet water levels rising and falling are that a waste pipe could be pitched incorrectly, which can make the water settle to a new level or there is a hairline crack in the porcelain in the trap that is causing a slow leak. But it’s usually the air vent that causes the water level to rise and fall.

Howdrain plumbing works

When you pour liquid from a can, youll notice that it doesnt flow evenly unless you have a second opening for air. The same holds true for plumbing vent pipe. 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, its probably a blocked drain or plumbing vent pipe that needs to be snaked out. And since the water in the toilet is dropping and gurgling, its 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.

Check out these 5 brilliant ways to unclog a toilet without a plunger.

Figure A: Common Example of Poorly Vented Drains

Bathroom plumbing venting in this system is missing, or the vents dont open to free air.

plumbing vent diagram - signs of bad ventilation Family Handyman

Next, check out these 10 silent signs that you have a major plumbing problem:
1 / 10