Very seldom will you be presented with one option when it comes to things like supplying or removing air from your home. The reason for this is that there is so much variation in housing design and structure that one single option will exclude a vast number of the population.
So, when it comes to venting your plumbing vent, the roof may be the most popular option, but it is certainly not the only one. Just for clarification, here we are discussing stack vents, not just any plumbing vent pipe in the system.
Plumbing vents can also be vented through walls and soffits. However, if these locations violate any of the plumbing vent termination requirements, then the stack vent has to go through the roof. It is less likely that the roof location will violate these requirements.
Plumbing Vents Don’t Have to Go Through the Roof
Section P3103.1 of the IRC states:
“Vent pipes terminating outdoors shall be extended to the outdoors through the roof or a sidewall of the building in accordance with one of the methods identified in Sections P3103.1.1 through P3103.1.4.”
From this regulation, we can clearly see that the homeowner has at least two options: the roof and the sidewall.
However, there is one more viable option for venting your plumbing exhaust. This one is not stated as explicitly, but it is permitted if we examine the code properly. This third option is venting through the soffit.
Section P3103.3 of the IRC talks about making vents through the soffit weathertight with caulk. They would not state this if venting through the soffit was prohibited.
So, as long as all the other plumbing vent termination regulations are met, you have the option of roof (through the roof, not into the attic), sidewall, or soffit (through, not into).
Rooftop venting is probably the most common route. This has several beneficial implications:
- There will be more professionals willing to install roof plumbing vents.
- These professionals will be more experienced in doing so, and the job is more likely to go smoothly.
- With more offers come potential savings since you can compare prices between several professionals.
- If you’d like to install the vents yourself, a more common placement means that more materials, such as websites, guidebooks, and videos, will be available to guide you.
Additionally, venting up through the roof means that you almost completely eliminate the risk of the gases getting trapped against your house, as can happen with soffit and wall vents.
Installing vents on your roof also means that they will be relatively out of sight. This can aid your home in looking more aesthetically pleasing.
Although rooftop venting is a very popular choice, there are plenty of disadvantages that come with choosing this option.
First of all, roofing material is very difficult to cut through.
This is a necessity since rooftops must be impervious to the elements, but the nature of roofing materials makes cutting through them a challenge.
Additionally, once the robust roofing material is cut through, you are introducing a leaking risk into your home.
Although you can patch up the empty space between the plumbing vent and the roofing material with flashing and caulk or something similar, no seal is perfect and there is still a risk of leaking if the job is not done perfectly.
Venting your plumbing vent through the roof can also make clogging a very real issue because when a plumbing vent is located on a roof, there is nothing shielding it from blockages.
These blockages can result from frost and ice buildup, nesting materials from animals, and plant debris.
Since a plumbing vent has to both allow air to escape as well as enter the pipes, blockages are detrimental to the function of the system.
Clogging of plumbing vents leads to negative pressure buildup, which does not allow the plumbing utilities connected to this plumbing vent to work at their best.
Signs that your plumbing vents are clogged include gurgling sounds in your pipes, standing water in your bathtub or shower, as well as the smell of sewage.
When compared to roofing material, walls can be much easier to cut through to install plumbing vents.
However, this is not the case if your walls consist of brick or concrete panels.
A horizontal stack vent rather than a vertical one comes with the advantage of it being less likely to become blocked.
This is because nesting animals such as squirrels will have a harder time getting into a sidewall vent because of the lack of a platform beneath it. Animals would have to either fly right into the small opening or scale up the side of the home, which can be quite difficult.
Additionally, if venting through the sidewall is a closer alternative to venting through the roof, this can be an advantage.
With a shorter venting distance, less venting material can be used and more time can be saved when installing the vents since the pipes don’t have to travel as far.
This leads to both money and time being saved.
Although rain getting into the plumbing vent system is not a huge deal, wind entering the system can create some issues.
Wind blowing near the opening of a plumbing vent can decrease the air pressure inside the plumbing vent, creating negative pressure.
A negative pressure system in your plumbing vents can cause problems in the flow of your plumbing and lead to odd sounds, gross smells, and overflow catastrophes.
Sidewall venting also involves the disadvantage of it being difficult to terminate the vent away from openings of the home.
The IRC requires that plumbing vents be a certain distance away from openings to the home and, with the home’s sidewall being the location of many openings of the home, including windows and doors, avoiding openings can be quite difficult.
Additionally, some climate zones may not allow sidewall venting.
In colder climates, there is the concern of freezing plumbing vents when they are exposed through the sidewall rather than the roof. This is the main reason why some zones may not allow this location for venting.
To make sure you’re complying with both international and local building regulations, it is wise to check with your local building codes to ensure that sidewall venting is allowed.
Soffit venting may not be as common as roof venting, but there are some scenarios where it is helpful.
Installing vents through the soffit can be far easier than doing so through roofing material as well as sidewall material. Soffit does not have to be durable to combat weather and is, therefore, easier to cut through.
Because the soffit is located under the eaves of the roof, the area is fairly well-protected from the elements, including one that can cause problems in your plumbing system: wind.
Wind would have to move underneath the eaves and up to blow near the opening of the soffit. This is fairly unlikely, which means that you are less likely to experience low air pressure related to this that negatively impacts your plumbing system.
The hidden nature of the soffit also makes it far less likely for animals to nest in it or for stray leaves or debris to clog the vents.
Although it is possible to vent a plumbing vent through the soffit of your home, this configuration can present some problems.
The location of the soffits under the eaves of the roof creates some problems relating to compliance with the IRC.
Roofs often extend past the walls of the home for aesthetics as well as to protect the home from various weather conditions.
This creates a problem since this overhang may be located near the property lines. Plumbing vents must be at least ten feet away from property lines, which can create problems when venting through the soffit.
The soffits also often hang over openings such as doors and windows. This can make it difficult to comply with the IRC since vents must be a certain distance away from openings for the safety of the inhabitants of the home.
Additionally, when sewer gas from the plumbing system passively travels through the plumbing vents and through the soffit, it may be more difficult for the sewer gas to be dispersed so that it does not create health concerns for those in the area.
The sewer gas may linger under the soffit, a situation compounded because of how unlikely it is that wind will enter this space to help disperse the gas.