Most of us think that plumbing is just about drainage and pipes. Plumbing has got a wider meaning and it involves many more things than what we presume. Venting of drains is something most of us are ignorant about. It is important for the drains to have vents to let out the toxic gases that can build up in the system. If there is no proper venting then these gases will start flowing back through the toilet and kitchen sink into your house which can be hazardous. When water is flowing through the drains with a bubbling noise then it means that your drainage system is not properly vented. Call the plumber and see what he can do to vent the drainage system. Moreover an adequately vented drainage pipe will be able to maintain a neutral pressure thus helping with the drainage process. Such drainage systems are found in old houses. No vent drainage will slow the process of drainage and will flood your house with poisonous gases.
An ideal drainage system will have two kinds of vents that include a wet vent and a dry vent. The stack is what is called the wet vent. It constitutes of a 4 inch pipe that is long enough that it runs from the sewer connection to a few inch lower than the roof of the house. All the drainage pipes are generally connected to this stack. It is called wet vent because it carries all the waste water along with the waste. Drainage pipes will have a Ptrap to prevent gasses from entering the house. A wet vent is not enough to vent the gases your plumbing system should also have a dry vent.