Why are there Pipes on my Roof – The Experts Explain

When looking at rooftops in your neighborhood, you might get curious as to why there are pipes popping out of the roof. The pipes that you see are an integral part of the Drain-Waste-Vent (DWV) system of any house. Albeit hidden by walls, floors, and ceilings, they are essential to maintain the equilibrium of the whole plumbing system. They provide two essential functions: drainage and venting.

So, why are there pipes on my roof? The pipes on your roof are known as plumbing vent pipes. They are responsible for letting air into the plumbing system and preventing sewer gases from remaining within the house. The reason why they need to be placed on the roof is to keep away unpleasant fumes.

As the experts from Better Homes and Gardens explain, these two functions ensure that the whole plumbing system remains healthy and functional. Drainage is what enables the drain pipes to be subjected to the appropriate air pressure at all times. This allows them to function smoothly and to promptly get rid of sewage and greywater from fixtures. 

According to research published in Water Supply, the negative pressure that a clog could bring about can lead to the intrusion of microbial and chemical contaminants into your water stream. Thus, drainage is paramount for your health.

The venting function, instead, is what permits to keep away unwanted sewer odors. The need to let these fumes dissipate quickly explains why vents are situated on the roof, far from windows or air conditioning systems.

Should My Roof Vent Pipes Be Covered? Here is the Truth

At least two types of covers are available for vent pipes: the so-called boot, which is a rubber cover, and metal caps. But do vent pipes need to be covered? The answer is not univocal, and different factors need to be taken into account.

Many people believe that they need to cover their plumbing vent pipes to protect them from rainwater. This is not necessary, as vent pipes are connected—through the plumbing system—to the water system. Thus, they are capable of eliminating excess water by themselves.

Furthermore, covers can lead to poor venting by partially obstructing the rooftop vent pipe. This is particularly worrisome in winter, especially when it comes to metal caps. Low temperatures can cause the formation of ice on the underside of the cap, thus choking the vent pipe.

More generally, covers can deteriorate due to extreme weather conditions, which are ever more frequent. In sum, as a general rule, you do not need to cover your vent pipes.

So, when it is a good idea to cover your plumbing vents? If you live in a stormy region and are worried about the possibility that debris might enter your rooftop vent pipe, it may be a good idea to consider some coverage. However, if you are unsure about the best solution for you, it is always a good idea to rely upon roofing professionals.

Can a Rooftop Vent Pipe Cause a Roof to Leak?

A smoothly functioning plumbing vent pipe system will not make your roof leak. However, roof vents are susceptible to various kinds of damage. For this reason, they should be subjected to checks on a regular basis, as leaks might be dangerous for your house and health, as the American Public Health Association has underlined.

However, if a leak does happen, it might be useful to know that the most common causes of leaks are:

  • Damage of the Rooftop Vent Pipe Collars. The collar is the part surrounding the base of the rooftop vent pipe, around the spot where it penetrates the roof, and it creates a seal that keeps rainwater and debris out. However, if the collar is worn out or has been exposed to harsh weather, it can leak water seep through the roof.
  • What to do? If the collar has deteriorated, it needs to be replaced. An additional solution would be to install flashing around the base of the rooftop vent pipe.
  • Damaged Pipes. A sign that will immediately inform you of potential damage to the roof vent pipe is if any drain in your house or building is leaking wastewater. The leaking occurs because the positive pressure of the air isn’t properly released in your pipes, but is instead pushed back on the water, causing the reflux of wastewater.
  • What to do? If something, for example a storm, caused some damage to your rooftop vent pipe or parts of it, they will need to be replaced. Repairs should be performed by a professional, as they entail a certain level of risk.

How Do I Seal Around the Pipes on My Roof?

Normally, homeowners will call an expert roofer or plumber only when they notice the dreaded brown spot on their ceiling. By that point, the risk of water breaking through the ceiling is very high, as it is the possibility that dangerous mold has formed, that can harm you and your family.

Once a roof has been affected by leakage for a long time, it can be very costly to repair. Plus, even after you repair it, thus killing the mold, the latter can remain allergenic for a very long time. Therefore, it is important to prevent leakage, taking appropriate actions before it happens.

The easiest way to prevent leakage from your vent pipes is to install a rubber collar, also known as pipe boot, around them. Rubber collars cover the existing rectangular metal flashing around the pipes, thus providing extra protection. However, be sure to keep in mind that rubber pipe boots do not last forever. On the contrary, they need to be replaced, on average, every 10 years.

With that being said, a reliable pipe boot shouldn’t be a hassle to find, so be sure to take a look at this highly rated choice from EAGLE 1. Provided through Amazon selection, here!

Another—more long-lasting—way to seal around the pipes on your roof is to completely replace the collar around the vent pipe. If this flashing was not properly installed, in fact, it can cause your roof to leak, especially in adverse meteorological conditions.

The technique is relatively simple. All you need to do is unscrew the original vent pipe flashing, carefully remove it, and substitute it with a new one, taking care to secure the new collar with silicone to prevent any future leakages.

Finally, for minor damages, you can simply use a putty knife to apply roof cement if the crack is in the sealant around the vent pipe. A waterproof silicone-based caulk is instead more suitable if the damage is situated on the metal collar or on the rubber boot. Just apply either product until it fills the crack, and you should be safe from further leakage for several years.

Here a table that analyzes reasons that are reported on what can cause damage to rooftop vent pipes:

Common damage to rooftop pipes Percentage of total results
Snow and rain may cause damage to rooftop pipes33.33%
Rooftop Pipes can be affected by high-wind speeds and carried debris5.55%
Damage to pipes can be produced by heat from the sun11.11%
Animals can occasionally damage rooftop pipes11.11%
Rooftop pipes are susceptible to damage from foliage and branches22.22%
Rooftop pipes sometimes are poorly assembled and aren’t sealed properly16.66%
Data derived from plumbing forums online

Here is an informative video on the process described above.

Best Roof Location for Sewer Vent Pipes: 5 Simple Tips

Sewer vent pipes are a part of a fundamental yet fragile system. Thus, nothing can be left to the case. In particular, the International Plumbing Code (IPC) established the guidelines for a vent pipe positioning that guarantees the functionality and safety of sewer vent systems.

In particular, these should:

  1. rise at least 152 mm (6 in.) above the roof as a general rule, or 610 mm (24 in.) in snowy regions;
  1. measure at least 51 mm (2 in.) in diameter and extend for 305 mm (12 in.) inside an insulated area inside the building before extending through the roof in snowy regions;
  1. be a minimum of 305 mm away from any vertical surface, such as the sidewalls of an upper story of the building;
  1. be located no closer than 3 m (10 ft) from the nearest window, measured horizontally, or 60 cm (2 ft.) above the nearest window or other openings, measured vertically. 
  1. This responds to the need of having any foul odor evaporate and not re-enter the house.

In sum, to be safe and functional, vent pipes should be positioned away from any opening and be wide enough to perform their tasks even in adverse weather conditions.

How Do You Clear a Roof Vent Pipe: A Guide in 5 Easy Steps

A common question when it comes to unclogging roof vent pipes is whether this can be done DIY, or if it is necessary to call a professional roofer every time. In principle, you should be able to unclog the pipes on your roof by yourself in two situations: when the clog is situated at the opening of the rooftop vent pipe, and when the pipe is not yet completely obstructed.

  1. Security First. Climbing your roof is a dangerous operation. If you do not feel comfortable working at great heights, consider asking someone for help or hiring a professional plumber. At any rate, make sure you have someone assisting you throughout the entire operation.
  2. Find the Vent Pipe. Make sure that you operate on the right pipe. You should look for a 3-inch tube made out of PVC or cast iron. To confirm that that is the vent pipe, have someone inside the house flush a toilet: if you hear gurgling, that is the tube you need to operate on.
  3. Start Clearing Debris Around the Pipe. Firstly, this move will give you a better visual of what is going on inside the pipe, so that you can determine if you can unclog the pipe alone or if you should call a professional. Secondly, in many cases, the clog is formed by debris on the outside of the vent pipe. In such cases, just cleaning around it will allow the pipe to function again.
  4. Remove the Clog with a Plumber’s Snake. This simple instrument, also known as a plumber’s auger, will allow you to remove clogs that are far away down the pipe and out of your reach. A great choice that won’t require you to have a drill or other supplemental tool is the all-in-one Plumber’s Snake by POPULO. Check out pricings from Amazon here. If you cannot reach the clog, it probably means that it has formed at a T-joint or in another delicate spot. In this case, consult a professional.
  5. Use a Garden Hose to Clear the Vent Pipe. Sometimes, the plumber’s snake will not be able to remove the entirety of the clog. If this happens, feed the end of a garden hose down the vent and have your assistant on the ground turn on the water. A sudden whooshing sound will be the sign that the vent pipe has successfully been cleared.

Does a Plumbing Vent Actually Need to Penetrate the Roof?

If you are renovating your house or installing new fixtures, you might be wondering whether vent pipes must go through the roof, as this might bring about extra costs. Although rooftop vent pipes normally go, as the name suggests, through the roof, this is not a strict requirement according to the International Plumbing Code.

A common alternative—provided that the local building codes allow it—is to have vent pipes that go through an external wall. However, if you decide that for you it is more convenient to have vent pipes going through a back wall or the attic, you should know about the extra precautions that it is necessary to take:

  • The rule that vent pipes cannot be less than 10 feet (3 m) horizontally from openable windows or other air intake openings is confirmed (unless they are placed at least 3 feet above the openings). If you live in a crowded area, this rule applies both to openings in your building and neighboring buildings.
  • Vent pipes should not be placed less than 10 feet (3 m) from the property line, once again for hygienic-sanitary reasons, as the sewer gases need to have enough space to disperse in the air.
  • Make sure that the vent pipes are placed at least 10 feet (3m) above the ground, to avoid any potential health hazards. Sewer gases need to be as far away as possible from where people live.
  • If you have other types of vents on your roof, vent pipes cannot go right under the soffit, as the gases coming out of them might contaminate the other streams of air and be reverted into the house.
  • If you want to place vent pipes that go through an exterior wall, the risk of them being blocked by rodents or other animals is increased. Therefore, it is important to provide some kind of coverage.
  • Finally, in climates where the 97.5% value for outside design temperature is less than 0°F (-18°C), vent pipes installed on the exterior of the building should be protected against freezing by insulation or heating.

Aron Blake

I am the lead copywriter on Homezesty and the Webmaster. I have a lot of experience in home renovations and the creation of style. I enjoy writing and sharing my tips on how to create the best living environment. My Linkedin Profile, My Twitter Account

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