Originally Posted by isola96
With all respect Redwood if you have a tiger growling in your sink or you have a big bubble shoot up in toilet when flushing its a vent issue not saying this is just for feature reference
No disrespect taken, venting is one of the most misunderstood parts of plumbing...
Fixtures will drain quite well without any venting at all, and in many cases too well which brings us to the reason for venting. Venting protects the trap seal by allowing air to break the siphon keeping water in the trap after the drain is used. S-traps are a prime example of this especially that toilet flushing noise at the end of the draining with the water being sucked out of the trap.
The only time a fixture will not drain due to venting is if the drain is going to a closed container where air needs to escape in order for the liquid to enter the container. This would include things like a sealed sewage ejector pit. Certain conditions may mimic this such as a clogged line, double trapping, or a severe belly in the line in which venting may mask the symptoms of the underlying problem. Sewers will accept waste without any problems unvented as will most septic tanks.
Here are a couple of You Tube Video's done by a Tech School Plumbing Teacher in New Hampshire to illustrate vented vs. unvented sink drainage on a mockup in his classroom.
As you can see the difference between vented and unvented draining is insignificant.
The venting of fixtures often relies on the flow of air through the pipes connecting the fixtures together. When pipes become flooded due to a clog air will bubble up in numerous fixtures throughout the home depending on the design of the drainage system and the extent the pipes are filled as vents are cut off by water in the pipes.
Something not draining is caused by a clog and almost never caused by venting except under the conditions I outlined earlier.
In the case a toilet the design of the toilet itself is that of an unvented fixture with a s-trap and the air gulp at the end of each flush is the trap siphoning dry. Of course the trap seal is replenished by the fill valve as the tank refills after flushing. The toilet not flushing will prove to be one of 3 causes and venting is not one of them.
- There is insufficient water going into the bowl from the tank to cause a proper flush. The internal passages of the toilet may be blocked slowing the flow rate, the tank water level may be too low or, a badly worn or, improper flapper is closing too soon.
- There is a clog or, restriction within the trapway of the toilet.
- There is a clog in the drain line from the toilet.
Additional troubleshooting or, information is needed before any correct answer can be given.