Why is My Bathroom Fan Dripping?


If your house was constructed within the past 20 years, then it probably has an exhaust fan in its bathroom. The main purpose of a bathroom fan is to eliminate all the moisture that builds up in the bathroom after you take a shower or bath. The fan can even get rid of bad odors from the bathroom.

However, there are times when a bathroom fan might drip. This can become a big problem because it will add moisture to your bathroom rather than take it away.

The bathroom fan starts dripping when warm moist air condensates in an uninsulated or poorly insulated ventilation duct. As the condensation forms on the wall of the ventilation duct, it begins to drip back down into the bathroom.

A leaking bathroom fan can stain ceilings and even cause moisture damage. It is important to figure out what is causing it.

The next paragraphs will help you find out exactly why it is dripping and how to fix it.

Bathroom Duct Condensation

During the winter season, it is normally much colder outside than it is on the inside. If you normally take hot showers in the bathroom, then it will be even hotter in the bathroom during and after your shower.

Where do you think all that warm moist air from the shower goes? It goes through the exhaust fan and air duct.

An uninsulated air duct in an attic is usually around the same temperature as the outdoor temperature, which is cold in this scenario.

Insulating the duct will prevent the bathroom fan from dripping, there will be no brown spots around the fan and the lifespan of the duct is increased since it will be dry and won’t rust.

If you remember your science class from high school, then you know that moist warm air will condense whenever it makes contact with cold air. As a result, condensation will form in your air duct.

In a previous article where I discuss why range hoods drip I have listed detailed recommendations on what to use to insulate the duct.

You may notice water dripping down from the exhaust fan as soon as you get out of the shower. It could also take a few minutes for the water to drip down after you have gotten out of the shower. It all depends on the size of your house and the length of your air duct system.

Condensation can form in the summertime too, but for a different reason. People like to blast their air conditioners inside their homes during the summer.

If your air conditioner is set to a low temperature, then cool air could make its way inside your air duct. Then, after a shower, the moist warm air hits the conditioned air and causes water to drip from the bathroom fan.

If you don’t want to/ are unable to insulate the duct and the bathroom is facing an exterior wall you could install a new fan on the wall instead. This requires no ductwork and can be done in an hour.

Read my article can a bathroom exhaust fan be mounted on the wall if you wish to learn more.

Bathroom Vent Leaking After Snow

Another reason for a leaky bathroom fan is when you have a lot of snow or ice on your roof. The accumulation of snow and ice may cause a bathroom fan leak as soon as those outdoor elements start to melt. This could happen as the moist warm air passes through the exhaust fan and comes out of the bathroom vent cover on the roof.

When the warm air makes contact with the snow and ice, these elements will melt into water. The water will flow through the vent cover, down the air duct, and out from the bathroom exhaust fan. Then you will have dripping water coming out of your exhaust fan.

When the warm air makes contact with the snow and ice, these elements will melt into water.

Water Dripping From Bathroom Exhaust Fan When it Rains

It might seem obvious that water will accumulate on your roof when it rains outside. However, a fully functional exhaust fan system is supposed to prevent rainwater from entering through the vent cover on the roof. But this might not happen if certain conditions exist.

The problem is that rain could leak down into the bathroom if the vent cover is defective or not installed correctly. The vertical slope creates an easy path for rainwater to flow into your bathroom fan once it is in the air duct.

Below we discuss how you can remedy the problem.

How to Stop Water Dripping From Bathroom Fan

Now you know where the water leak originates. Everything from condensation to rain, water, and snow can cause a leaking bathroom exhaust fan.

A properly functioning exhaust fan system should not leak water back into your bathroom. So, if you experience a leak from one of these natural elements, then it means something is wrong with your exhaust system, and it needs to be addressed.

Nine times out of ten the leak is caused by inadequate duct insulation.

Replace or Add Insulation

The air duct should have insulation on its outer walls. The purpose of the insulation is to separate the warm air that is vented out from the bathroom from the colder air that is in the attic. This will avoid condensation.

This insulating sleeve from Amazon makes it very easy to add insulation to an existing duct. Make sure you order the right dimension and enough to cover the entire length of the duct.

The air duct should have insulation on its outer walls.

If it is cold outside, then it means your air duct is cold too. That will cause condensation on the walls of your air duct. That is why if you notice water dripping out of your exhaust fan after you have showered then your insulation is probably the problem.

The solution is to replace your insulation with more robust and better-fitted insulation. Most likely the insulation has slid down over time and the top part of the ventilation duct is left uninsulated.

You might want to call a professional handyman to perform this task if you’ve never done it before. It requires a certain level of skill to ensure the insulation is fitted just right.

Replace the roof vent cover

When you first notice a bathroom exhaust fan leak, you’ll want to inspect the roof vent cover(louver) immediately. When the leak occurs only when it is windy and rainy, nine times out of ten, the cover will likely be the source of the problem.

Sometimes heavy winds, flying debris, and other outdoor elements can cause damage to the louver. Since it is on your roof, the cover is in an area of your home that suffers the most impact from nature. If you find a bad or defective vent cover on your roof, it means that water can pass through it.

Therefore, you’ll want to inspect the roof vent cover and make sure it is not damaged. Sometimes it is not the cover that is damaged, instead, it has been installed incorrectly and water is leaking from the outside of the vent duct. Then its best to have a professional replace it as soon as possible.

Replace the Fan

Bathroom fans do not last forever. If you shower every day and use your exhaust fan to eliminate the moisture in your bathroom each time you shower, then your fan will probably wear out after 5 to 10 years.

Older fans tend to slow down and have more trouble pulling moisture out of the bathroom. Because of this, a lot of that moist warm air won’t make it to the vent cover on the roof. Instead, the warm air will stay trapped inside of the air duct with all the cool outside air. This will cause condensation to form.

Find out how bathroom exhaust fans work

If you’ve already verified that your insulation and roof vent cover are in good condition, then you probably have to replace your bathroom exhaust fan. In most cases, you will have to upgrade to a more powerful bathroom fan that does a better job of pulling out the moist air from the bathroom. Check out my other article if you want to find out how to remove the old fan.

The home ventilating institute recommends that you keep the fan running for at least 20 minutes after the shower. The moisture does not get pulled out immediately after you flick the switch on the wall. You need to give the bathroom fan some time to eliminate all the moist air from the bathroom.

I recommend a longer period than 20 minutes. Check out my other article where I discuss this in more detail.

Use a Dehumidifier

If you’ve tried all three of these solutions but continue to have water leaking from your bathroom fan, then your only solution left is a dehumidifier. A humid outdoor environment could potentially affect the humidity level on the inside of your home. It could affect the humidity in your air duct as well.

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Joonas Pütsepp

I like it when I'm able to fix everything that needs fixing around the house. In order to do that, I have to do a lot of research. This site will cover everything I learn and maybe help others do the same.

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