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Can Bathroom Fan Be Vented Using PVC Pipe

Ducts with a smooth inner surface are the best for exhaust systems. While they are mandatory for range hoods and dryers, they are not required for bathroom fans. Flexible ducting is much more affordable, so many people give up smooth ducts. But PVC piping represents the best of both worlds.

However, piping materials are regulated by code. So, PVC is only the solution if it’s allowed. And if it is allowed, you also need to know the benefits and drawbacks of this choice as well as any linked regulations.


PVC pipe can be used for bathroom fan venting provided that it has a flame spread index of less than 200. PVC Schedule 40 foam core pipe is the perfect material for venting ducts as it is designed for drain, waste, and vent purposes.

PVC Pipe Ducting Appropriate for Bathroom Fan

According to Chapter 16 of the International Residential Code (IRC), the materials for all HVAC duct systems must conform to industry standards.

Section M1601.1.1 says that ducts must be listed and labeled according to UL 181, must have a flame spread index of 200 or less.

After extensive research, I cannot discover if PVC is UL 181-listed without purchasing the standard. As this costs between $700 and $1,600, I decided against getting a copy of it. However, if you called a local professional, they would likely have access to the standard and could tell you if PVC qualifies.

With regards to the other requirement, PVC has a flame spread index rating of less than 10, so it more than qualifies.

You also have to consider local codes and regulations, which can differ from state to state as these take precedence over the IRC. We can still look at the IRC, though, because local state codes are adapted from the IRC.

Our informative article, What Kind Of Duct To Use For Bathroom Fan, explains the different types of bathroom fan ducts.

Requirements of PVC Pipe for Venting Bathroom Fan

When using PVC piping to vent your bathroom fan, check the regulations in your area for the type of pipe that can safely be used. Some considerations when using PVC pipe are:

  • The PVC pipe should be for drain, waste, and vent purposes only and suitable for gravity-fed waste elimination systems.
  • The PVC should be designed for non-pressure systems with temperatures not exceeding 140 °F (60 °C).

PVC Schedule 40 Foam core pipe is the ideal pipe for bathroom fan venting. This type of piping is non-toxic, easy to install, and is code compliant. The PVC pipe fittings can be safely cemented and sealed, preventing any water that might collect in the pipe from leaking and causing water damage.

An added advantage is that PVC Schedule 40 Foam Core has a lightweight cellular core and is co-extruded. This means that while the walls of the pipe are solid PVC, the inner core is foamed (or cellular) PVC, making the pipe lighter.

Certified cellular foam PVC piping should have the certification number ASTM F 891 stamped on the pipe.

The PVC piping needs to be as straight or as rigid as possible. Bends in the pipe increase static resistance causing problems for the fan. If your designs include bends, use long-sweeping elbows rather than short bends to improve circulation.

Our informative guide, How Bathroom Fans Should Be Vented | A Complete Guide, provides more information on venting bathroom fans.

Does PVC Pipe Need to Be Insulated

PVC pipe should be insulated when used as a ducting material for bathroom fans. Insulation prevents moisture build-up and condensation on the inside and the outside of the pipe.

In warmer climates, the indoor temperates are generally kept low, which causes condensation to form on the outside of the duct pipes. Water can drip from the pipes causing moisture damage to the fittings and the ceiling.

When hot, moist air is vented through the duct in colder climates, it connects with the cold duct, and condensation forms inside the pipes. The water could eventually drip down, causing unseen damages.

An uninsulated duct could cause a bathroom fan to drip, causing unsightly brown stains around the fan.

This Is Why PVC Pipe Is Good for Venting

PVC piping is an excellent material to use for venting your bathroom fan as long as the correct type of pipe is used. PVC creates a better seal than metal, so you won’t experience any problems with leakage as you could with using metal ducting pipes.

According to various online sources, PVC pipes are the material of choice for ducting. Here’s why:

  • PVC is durable and safe. The lifespan of PVC piping is expected to be 100 years or more, so it could outlast the fan itself.
  • PVC foam core pipe is less rigid and lasts even longer than standard PVC pipe.
  • The core inside the PVC foam core pipe insulates sound, muffling any noises from the vent.
  • Tightly sealed, leak-free fittings prevent water loss and costly water bills.
  • PVC is free from bio-film contamination. Bio-film breeds bacteria and mold, which will not breed in an adequately sealed PVC pipe.
  • Fewer materials are used for the manufacture of foam core PVC, making it more cost-effective.
  • PVC is a lightweight material that does not rust, corrode or scale.
  • PVC is a low carbon plastic making it recyclable and sustainable.

PVC Pipe Has Drawbacks as a Ducting Material

Even though PVC piping is our material of choice for ducting material, it is not perfect. PVC piping does have a few disadvantages and limitations which could influence your choice of materials:

  • PVC pipes are not flexible. Maneuvering the pipes through the ceiling or roof can be difficult, limiting your installation and placement options.
  • Once PVC pipe is cemented to the fan, it is difficult to remove and will need to be cut off should you need to replace any components or relocate the fan or the vent. The PVC pipe might not be salvageable and may need to be replaced with a new one, adding additional costs to the repair or relocation of the fan.
  • PVC piping can become brittle in lower temperatures and is prone to cracking when exposed to freezing or colder temperatures over an extended period of time.
  • PVC piping has different rated strengths. If the wrong strength is accidentally used for a particular job, the outcome might not be as expected. The pipe might not last as long, and the installation could fail.

How to Connect PVC Pipe to Bath Exhaust Fan

Before you connect any piping to your bath exhaust fan, check the building code requirements and install according to the manufacturer’s directions.

Requirements:

  • PVC pipe
  • Heavy-duty clear PVC cement

Method:

Connect the PVC pipe to the bath exhaust fan using PVC heavy-duty cement. This forms a secure water-tight bond and a properly seated joint with the fan exhaust. The best glue to use for this is a specialized PVC cement that uses chemicals to weld the PVC pipe to the exhaust vent port.

You will need to cement the pipe in place to ensure that moisture does not leak from the join and cause moisture damage to your ceiling or roof.

Sources

https://codes.iccsafe.org/content/IRC2021P1/chapter-16-duct-systems

https://findanyanswer.com/goto/440535

https://pvc4pipes.com/pvc-pipes/why-pvc-pipes/

https://www.thisoldhouse.com/bathrooms/21016701/how-to-install-a-bathroom-vent-fan

https://homeguides.sfgate.com/insulate-pvc-23600.html

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