Dryer vents perform the crucial act of moving moisture and hot air outside your place of residence. The ductwork of a dryer is exposed to heat, moisture, and flammable lint, so it needs to be able to handle all of these with minimal risk to safety and appliance effectiveness.
You may be tempted to use PVC piping because it is one of the cheaper options and works well as ducting for other household appliances. However, this is one of those situations where you just need to bite the bullet and spend a little more on metal ducts. Let me tell you why.
Dryers can’t be vented using PVC ducts. PVC’s maximum operating temperature is near to dryers’ operating temperatures, so PVC can warp. PVC also builds up static charge, which traps lint and increases the chance of sparking. Lint is flammable, so PVC creates a fire risk. Trapped lint makes dryers ineffective.
PVC Cannot Be Used for Dryer Ducts
PVC can be used for other home projects, like venting bathroom fans, but it cannot be used for dryer ducts.
The dryer duct environment makes using these plastic pipes dangerous and ineffective, which we will discuss shortly in detail. First, you should know that the danger is such that avoiding PVC in dryer ducts is not just a recommendation; it is an official regulation.
PVC Dryer Ducts Contravene Building Codes
According to Section M1502.4.1 of the International Residential Code (IRC), dryer exhaust ducts must be made of metal (at least 0.0157” thick). Thus, using plastics like PVC and ABS violates the building codes.
Consequences of Building Code Violations
What happens when you violate the building codes?
Well, firstly, it is unsafe to do so. The code exists to protect the health and safety of people; they are not random hoops for homeowners to jump through.
Secondly, contravening the building codes can lead to fines. If a home inspector comes to your house and finds it hazardous to you and your neighbors, you can be penalized for this and forced to make the change to achieve compliance.
So, while it may be cheaper to use PVC initially, if this usage comes to light, you can add the cost of a fine and metal ducting to the price of these PVC pipes.
Thirdly, if your house violates the building codes, then your homeowners’ insurance is in jeopardy.
Most insurance policies are dependent on the house being up to code. If your house burns because your plastic ducts caused a fire, then you will not be paid out for this. Imagine being without a home and without a way to pay for a new one or repairs.
Finally, if you plan on selling the house, you will be in a bad position. House sales usually involve some kind of inspection. If it is discovered that you have vented your dryer with PVC pipes, then the sale could fall through. What potential homeowner would be keen to buy a house knowing that a re-ducting project is top on the list?
Alternatively, you may have to lower the asking price of the house so that it is less the cost of replacing the dryer’s ductwork.
Local Building Codes
The IRC is applicable in most states. Some sections are used as it, but others are adapted and adjusted to each state in the local building codes. This means that you should check your local code for the final word on PVC dryer ducts.
However, as you will see in the following sections, this practice is unsafe. This means it is unlikely your state will allow it, and even if they do, it behooves you to stick with metal ducts.
Reasons for the Prohibition
As mentioned, not allowing PVC dryer ducts is not a purposeless regulation to make your life as a homeowner more difficult and expensive. There are very real safety-and function-related reasons for this prohibition.
Heat Intolerance Threshold
Dryers are heat-generating appliances. The average drying temperature of dryers is 125 °F to 135 °F (51.6 °C to 57.2 °C). These are not mickey mouse temperatures.
PVC has a recommended operating temperature of up to 140 °F (60 °C). This is very close to the average dryer temperature. Too close to be safe.
But what happens at and over PVC’s maximum operating temperature? The pipes won’t suddenly burst into flames—that happens at temperatures above 734 °F (390 °C). However, the PVC pipes will begin to warp and may even smoke.
Dangers of Warped Dryer Ducts
Warped ducts interfere with airflow and air pressures in the system, causing strain on the dryer’s motor, shortening its life, and reducing the effectiveness of the appliance.
Furthermore, misshaped ducts result in areas where water and lint can accumulate. The accumulation of these can cause mold to grow in your ducting. Lint build-ups also introduce another and more serious risk—a fire risk. I’ll tell you more about this in a minute.
As mentioned, PVC can start smoking once it gets hot enough. The fumes produced by PVC contain a higher amount of chlorine, thanks to the large presence of chlorine in PVC’s chemical makeup.
While a little bit of exposure to chlorine fumes will not kill you, extensive exposure can have negative health effects.
Exposure to any type of plastic fumes can cause respiratory issues, headaches, and irritation of the nose, eyes, and lungs.
Static Electricity Build-Up Inhibits Efficiency
Static electricity is able to build up on plastic pipes like those made from PVC. This happens because plastics are insulators, meaning that they do not conduct electricity very well.
As the dyer exhaust air flows through the PVC pipes, it creates a static charge. The lint that is carried in this air is readily attracted to the static electricity—just think of how much more likely you are to receive a static shock when you wear a woolen sweater.
Lint will begin to accumulate and will reach a point at which there is so much lint build-up that it affects airflow and diminishes the efficiency of the dryer. Your dryer relies on the movement of air into and out of the tumbler to dry the clothes. If this is impeded, the clothes will take longer to dry.
Furthermore, the motor has to work harder to move the air and can overheat and eventually fail.
A dryer that is under strain will use more power, so it can also make your utility bills increase.
PVC Pipes Are Fire Hazard
As I mentioned earlier, the fire risk with PVC pipes is not directly related to the PVC material as it is only flammable at extremely high temperatures. The risk is related to lint.
Lint is flammable regardless of what material you use for your ducts. However, with PVC ducts, the static build-up makes this risk exponentially higher than it is with metal ducts.
Not only will more lint accumulate in the pipes because of this static, but the static itself provides a ready source of ignition for the lint. One static electricity spark in a lint-lined pipe, and you have a duct fire.
Furthermore, if the temperatures are high enough to warp the PVC, then even more lint can collect in the grooves, bends, and twists, literally adding more fuel to the fire and being just as dangerous as foil dryer ducts.
Additional Dryer Requirements
In addition to the rule about dryer ducts having to be made from metal, the IRC has other important dryer duct requirements (Sections M1502.4.2. to M1502.4.8)
- Dryer exhaust ducts must not be deformed to fit into any space and must be securely supported at least every 12 ft (3.658 m).
- Ducts must be connected and sealed with the male end of the duct pointing away from the dryer. This ensures fewer places for lint to get stuck and reduces airflow interference.
- Fasteners cannot protrude over 1/8” (3.2 mm), or they will interfere with airflow and catch lint.
- Transition ducts must be a single length of duct less than 8 ft and cannot be concealed.
- Exhaust duct power ventilators must be installed as per manufacturer instructions, and booster fans are prohibited.
- The maximum length of dryer ductwork is 35 ft (10.688 m) or as per the manufacturer’s instructions.
- You can use elbows, but each elbow reduces the maximum allowable length as per Table M1502.4.6.1.