The house’s vent pipe allows sewer gasses to escape into the outside air above the house. It runs inside the walls of the house from the roof to the main drain pipe. When water enters the pipes, it drains away because air from the vent pipe eliminates the vacuum. Gravity takes over and the water drains down the pipe.
A good way to demonstrate this is to take a straw and suck up a little water. Place a finger over the top of the straw and lift it out of the glass or bowl. The water will not go anywhere because air is not allowed to enter above the water to break the vacuum. Remove the finger and the water drains out of the straw.
Over time, heat and cold from the seasons will cause any pipe to expand and contract. This can cause weak spots in the pipe wall and cracks can occur.
If there is a crack in the pipe, sewer gasses can enter the home and create an unhealthy situation. The smell will be evident; checking the sinks and toilets will not reveal any sewer water backing up into the house.
The problem will not solve itself; it will become worse and could require major repairs. Sewer gasses are unhealthy to breathe. For those selling a home, this situation must be remedied before the house will pass an inspection for sale.
Finding and repairing a crack in the vent pipe may or may not be a DIY project. The type of repair will depend on the material the pipe is made from. Cast iron and PVC pipes require different methods for repair. Before trying to make this a DIY repair, study the type of pipe in the home and determine if the handy person’s skill can safely handle the project. If not, a professional plumbing company should be called to locate the crack and make the necessary repair.
PVC pipe can be repaired by cutting the cracked part out and inserting a new piece of pipe. In line connectors, a hacksaw and PVC cement are required to make the repair. Dry-fit the connectors and repair piece first before cementing to ensure the proper fit.
Cast iron pipes can be repaired if they are not too badly damaged. Special fittings and connectors will allow the handy person to replace the cracked section with PVC pipe. The pipe below the repair should be supported by connecting it to a wall stud using metal strapping. This will prevent the pipe’s weight from placing undue strain on the new pipe section and repair joints. Keep in mind that a wall, floor or ceiling may need to be opened to gain access to the cracked pipe.