There could also be a clog in the pipe that services the water flow.
Slow drain roof vent.
If the air from the drain or toilet smells like sewage this can also be a sign that the vent pipe is blocked.
If the water moves slowly from bathtub drains or bathroom sinks the problem could be related to improper or inadequate venting.
The drain in the toilet bowl is basically a p trap.
If the problem just started it s probably a blocked drain or plumbing vent pipe that needs to be snaked out.
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.
If you notice that one or all of your drains are backed up and very sluggish it could indicate a vent issue.
How to unclog a toilet vent pipe.
When tubs and sinks drain slowly it may be an indication of an undersized or blocked vent.
If the plumbing air vent or vent stack becomes completely blocked a vacuum will form and you will no longer hear gurgling.
When the vent pipe is clogged it shows up within your home in a variety of ways from ghost flushing from your toilet to a sink that won t drain properly.
The odor of sewage.
But one of those issues pertains to a clogged plumbing vent.
Slow clearing drains if the drain just isn t clearing and you ve done everything reasonable to clear a possible clog in the drain your problem may be an obstructed vent pipe.
Elevated drainpipe pressure prevents water from draining off at an average rate.
If the vent line is obstructed it can cause a number of problems including.
Slow drains can stem from several issues.
However if every drain in your house is slow it s possible this is being caused by blocked vent pipes.
A vacuum is being created that is pulling things in the wrong direction.
Slow drainage slow drainage is probably the most common sign of poorly vented drain lines.
Your vent pipe can become clogged from a variety of things.
A single slow drain usually indicates a blockage in the drain itself.
You will also be able to smell sewer gases in the rooms where the affected fixtures are located.
Slow draining is one of the first signs of vent blockages but it s also caused by obstructions in the drain so you need to keep investigating to narrow the problem to a vent issue.
If you can t clear a slow flowing drain with a plunger auger or drain cleaner the vent blockage may be severe.
However if all of the drains in your home are slow and you re also noticing the other issues described in this section blocked sewer vents are more likely to blame.